Ask the A&Ps

Avoiding maintenance can be a good thing when what's recommended is unnecessary. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Dominick is questioning his mechanic's advice on prop overhauls. He has a Cessna 310 and his left rpm is too low on approach when the control is full forward. It's not an issue on the ground or on takeoff. His mechanic recommends overhauling the propeller, and since he's doing one he should do both. He swapped governors and that didn't change anything. He sent the prop back for IRAN and they didn't find anything significant. Paul suggests it's the low pitch stops. This is a classic twin owner trap, Mike says. The two engines are never the same. Everyone agrees that he can leave it as is.  Vas has an RV-10 and the Lycoming IO-540 has been acting up. During some flight training in the airplane, he noticed oil consumption went up, metal was in the filter, and he ended up overhauling the engine. He's wondering if he should have just pulled a cylinder instead. He was flying 140 hours a year, and he's wondering why he would get corrosion. Higher oil consumption isn't a corrosion problem, but the cam and lifter spalding do indicate it. These were unrelated problems, according to Mike. Paul thinks it's possible the damage was already in place when there was a previous IRAN. They settle on it being a lifter hardening issue, meaning poorly manufactured parts.  Jim has a Mooney M20K and an instructor showed him a leaning procedure while in cruise at 9,000 feet. They set the manifold pressure to 30 inches, the RPM at 2300, and then pulled the fuel back to 11 gph. That's how he's been leaning ever since. CHTs are in the 360/370-degree range. He trails the cowl flaps to try and cool the CHTs if it's a hot summer day. If the TIT gets too high he'll enrichen it just a touch. Paul said if he adds more fuel and the TIT goes down, he's running rich of peak.  Peter found some residue on the top of his intake valves on the engine on his 172N. He typically flies with autogas. He's wondering if can or should get rid of it, and if so, how to do it. Paul said people talk about it, but he's never done it. They suppose it's not carbon, but probably coked oil. They suggest a wobble test if he's really worried, but generally they think he can leave it alone. 

How much should a mechanic tell a client during an annual? Mike, Paul, and Colleen handle this question and more. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Justin flies a Twin Bonanza and cylinder 5 on his left engine takes as much as a minute to fire up and start running. It comes online fastest if he goes very lean quickly after starting. He's pulled the valve cover and springs off, and it's not a sticky valve, and he's reamed the valve guides. Mike wonders if it could be a primer problem. Justin disconnected the primer line, ran the boost pump, and checked for leakage and couldn't find any. Paul suggests taking the line off, capping off the injector, and then trying it.  Jorg is trying to make sense of his data. He has a K35 in Austria and he has GAMI injectors and an engine monitor on his IO-470. He has a low CHT on the number 6 cylinder, and it's the first one to go on the lean side, and it shuts down first if they go very lean. An induction leak test seemed fine, and his GAMI spread is less than a gallon an hour. The valve was also lapped. Mike said a low probability culprit could be if the bleed air holes in the injector nozzle were plugged, since they don't seem to have an impact at wide open throttle, but would at a reduced throttle.  Mark saw a Youtube video and is now wondering if there's danger lurking in the alternator. The video mentioned how an alternator elastomer coupler failure could lead to a catastrophic engine failure. Paul said the installation is critical because of some critical components. Mike thinks the video relies on old information. He said Continental used to employ a spring, which would come apart and throw large chunks of metal into the engine. The coupler is meant in part to protect the engine if the alternator seized, but sometimes the coupler would fail and cause its own failure. The newer versions have an elastic or rubber piece instead of a steel spring, which shouldn't cause an engine failure.  Chaz is an A&P/IA and he wants the team to weigh in on the debate as to whether the inspector should give pilots a full list of squawks or only the airworthiness issues. He personally thinks he should give the whole list so the owner knows where he stands. The hosts agree that the full list is preferable. The mechanic is giving a full slate of options, and not a required list. Airworthiness items can be listed separately or be flagged. 

Quick corrosion, long-lasting engines, and mobility mods are on tap for this episode. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: Patrick is looking for the right fit on a potential aircraft purchase. He had a shoulder replacement and lost some mobility in his right shoulder. He’s wondering if he could get an accommodation on things like flap controls. Paul suggests he look for an older Cessna with the progressive flap switch, not the one with pre-selected detents. The hosts thing that up/down progressive switch would be a minor alteration and just a few wires. The pre-select flap lever is probably a major alteration and a lot of work because there’s a lot going on behind the panel.   Jeff has a Maule M7 on floats and is battling corrosion. Recently he did a salt water landing, sat for about 3 hours in the water, flew home, and his left main gear didn’t rotate as he landed. He saw that the main forks had a bloom of corrosion that froze the wheel. He washed everything in fresh water, and then next day saw a bloom on the other gear as well.  He is wondering if he had a stray current given how quickly it developed. Mike thinks it’s unlikely because if the battery if off it’s completely isolated from the rest of the system, meaning their shouldn’t be a way for the battery to provide electrical current anywhere on the airframe.   Lindsay recently purchased a Piper Lance and wants to make sure she keeps the engine going as long as she can. They go over the basics and make sure she is boroscoping the cylinders, fly it regularly, etc.   Mark is wondering how soon is too soon to put in cowl plugs after flying. He has a Cessna 206 and he’s wondering if he can put in the cowl plugs right away. The concern is about the plugs, not the engine, Paul said. The hosts all agree that he's fine to seal the cowl off as soon as he likes.

Is going past TBO more expensive? Plus fuel vents and turbocharger temps. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below:   Mike wonders if running past TBO actually costs more. He has a Mooney and has heard that overhauls far beyond TBO can cost more as a result of having to replace more parts. That is an oft-reported myth, Mike says. The only things that can cause an up charge on most field overhauls are having to replace the case or the crankshaft. Otherwise it’s a fixed price. Paul says the top engine generally goes into the trash. On the crankshaft, they usually just have to polish it or grind it. There’s no repairing a crankshaft. If it’s bad, it was bad because it had some other type of problem. You can go thousands of hours on crankshafts. Mike said Lycoming had a white paper on their website that said crankshafts are generally good for 14,000 hours. Cracks on the case can be welded.   Mark has an early 182 and he’s having issues with the fuel caps properly venting. He has noticed that once you fill the tanks with cold fuel, there doesn’t appear to be an outflow vent. Paul said there’s a small weep hole that allows the expanded fuel to vent. But Mark’s tanks still aren’t venting. He pulled it out but didn’t seem to find a weep hole. He said it looks original and has an early Cessna part number. If the fuel is pouring out it needs to be replaced because the check valve is bad. The wing will balloon and can cause structural damage without a weep hole. He said when he removes the cap a big woosh of air will come out, indicating the fuel isn’t venting out as it expands.   Jim is wondering how TIT and EGT intersect. He flies a turbo Saratoga and has been experimenting lean of peak and rich of peak. He’s noticed a significant difference between EGT and TIT. If the TIT is farther away from the engine, he’s wondering why it’s hotter than EGT. He’s also wondering how hot he can let the turbocharger get. Mike said TIT is hotter because the EGT probe is only seeing gas flow for less than a third of the time, and only when the exhaust valve is open. The EGT probe actually measures a “probe” temperature that averages the temps over time. When the gas gets to the TIT probe it’s a constant heat from all cylinders all the time. Redline on his TIT is 1,650 degrees, which Mike said is a continuous operation limit. Paul asked what the exhaust system is made of because that matters. He suggests not exceeding the red line. In cruise, the lower you can keep the T**s, the longer the system will last. Mike limits his TIT to 1,600.

What exactly should we be looking for in our cylinders? Plus torque tales, making TBO, and overzealous manufacturers. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full show notes below: Jared asks what he should be looking for with his borescope. He’s seen bad valves and what that looks like, but he’s also hoping to see what bad scoring and other things. Colleen stresses to focus on what goes wrong with a cylinder, and being able to identify those attributes. Things like broken rings, piston pins, detonation signature, etc are identifiable, and can be examined. Paul said rust is always something to look for, but most cylinders have some. Knowing how much and why it’s there is what matters. Mike said rust would cause him to consider the camshaft on an airplane in a pre-buy situation, for example.   Chad has a new Cessna turbo 206. He wants to be sure to get to TBO and then some. Paul said the one thing he needs to do is fly as often as possible. He is flying 400 hours a year, which the hosts love. He asks if he can fly a maximum continuous power, and the hosts agree that he can, so long as his cylinder head temperatures are within spec. The book tells Chad to lean to peak turbine inlet temperature, and not to run lean of peak. He wants to know if this is a real threat or a hollow one. Once again, the hosts agree that it’s a hollow threat, and that he should operate lean of peak if he can. They also discuss the myth of turbo cooldowns. Mike said George Braly instrumented a turbo and found that it actually got hotter as it sat on the ramp “cooling down.”   Serrhel is sick of the Continental maintenance schedule. He has a Cirrus that is under warranty, and he’s required to do the maintenance as scheduled. At 300 hours an injector cleaning was required, and only a few months later, the injectors had to be cleaned again during the annual. Cirrus and Continental required it, even after some pushback. Paul said manufacturers don’t buy into the probability of maintenance induced failures or in the concept of reliability centered maintenance. The discuss the reasons why manufacturers think this way, and Mike said a conversation with a factory representative taught him that they basically don’t trust GA pilots and owners to maintain aircraft at a high level.   Patrick is throwing down a challenge to Paul. He said Paul always stresses that when tightening case through-bolts, you torque simultaneously with torque wrenches on both sides at the same time. Old Continental videos say the same, but the video shows the technicians only torquing on one side at a time. Despite the guidance, Paul said it doesn’t make sense to put a torque wrench on both sides at the same time. Mike said if you put a torque wrench on both sides, one side will be torqued dry and hit the pre-load spec too early. Mike and Paul then get into a debate about how the logbook entry should be made when if you decide not to follow Continental’s advice. Patrick further mentions that the Continental service manual doesn’t say it should be simultaneously.  

The definitive guide to owner maintenance, slipping starter adapters, and close CHT tolerances. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join

Creative leaning techniques, rusty cylinders, and odd manifold pressure indications are on tap this time. Send your questions to [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join

Old engines, rusty airplanes, and a strange valve incident are the puzzlers for Mike, Paul, and Colleen this episode. Send your questions to [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: John has a Beech Musketeer who had an unusual situation with his valve. The valve seat separated from the cylinder barrel and dropped down, striking the piston crown. He's wondering if he did anything to cause this, despite never exceeding 425 degrees CHT. The hosts agree that it was probably a manufacturing error, even though the cylinder had a few hundred hours on it. Mike said the only way this can happen is with a manufacturing problem or a high heat event. Larry has an early SR22 with 3,300 hours on the engine. It's not in need of an overhaul now, but Larry has read those early SR22 cases are more robust, and he's wondering when the time comes if he should overhaul or do a factory reman. The hosts aren't aware of any particular issues that make cases from that generation better, but they do offer some sound advice on the reman versus overhaul question. Mike said that if the engine has been treating him well that Larry should overhaul it. And if it's been a lemon, send it off and get a new one from the factory. Larry is a little worried about resale, since people are skiddish with high-time engines. Mike suggests that an airplane with run-out engines is the best investment because it's been fully depreciated. Any additional time is essentially free. Terry has been looking for a 182 and he saw one in California with corrosion. He wonders how much corrosion is too much. Paul said that according to Terry's photos, he wouldn't think twice about buying the airplane. The general rule is that you can take off only 10 percent of a structure and not worry about it. The skin on top of the wing where the corrosion can be seen is only 25 thousandth of an inch, which means you could only take off 2.5 thousandth of an inch and still use that skin. White splotching can be seen in the photos, and Paul said it's common for airplanes of that vintage, and not to repair it. Instead, he recommends spraying it with ACF-50 or Corrosion-X every few years. Doing so will stop the spread and not allow any further damage.

Pre-emptive engine overhauls, upgrading an old electrical system, spark plug anti-seize, and old wood wing concerns are on tap for this episode. Send your questions to [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: Lance inherited some furniture that had lived in the Midwest for 200 years, and began splitting after only a few years after he moved to Salt Lake City. He's wondering if the same concern would hold with wood wings, like those on the Bellanca Viking. The hosts say not to worry. The wood spars are lathered with a varnish that helps keep out moisture, Sitka spruce is resistant to splitting, and Mike said in his experience with Vikings in the 1970s, shops didn't report issues with airplanes that had lived in different parts of the country. Jim has an Arrow and he wants to guard against the long down times we're seeing at overhaul shops. To do so he wonders if she would pick the right time and pre-emptively overhaul his engine, or at least change out the cylinders. Mike, Paul, and Colleen fully lecture poor Jim on the perils of so-called top overhauls, and instead advise him to do nothing more than stock a cylinder in case the time comes and he needs it. Darren is thinking of putting an all-new panel into his Tri-Pacer, and he's wondering if he should upgrade his generator to an alternator when he does it. Paul said he's not worried about the generator when it comes to his avionics, but given that Darren flies at night, Paul thinks an alternator is probably a good idea. Steve is wondering about spark plug anti-seize compounds. He uses the Tempest and Champion products, but found Lycoming's service instructions that prohibits their use. It calls for a copper-based compound, or motor oil. The hosts think the guidance might be a result of getting the carbon-based anti-seize on the insulator, which would cause arcing. They all agree that motor oil would be a bad choice. Paul thinks the Champion compound is fine, so long as you use only a little, and keep it off the last thread. Mike now uses an anti-seize stick that you apply to the threads, almost like a lip balm.

A creative modification, lean of peak with turbocharging, electronic ignition, and oil leaks are on tap. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Tom has a turbocharged Mooney and he's wondering how to manage it while lean of peak. The hosts say the first goal is to get on the lean side quickly, and then fine tune once there. They argue you can hear and feel when you're lean of peak, which is how you can expedite it. Then check the CHTs and the T**s to make sure they are below limits. That's it. Paul said in that way turbos have an advantage because it doesn't at what altitude you lean, the numbers should be similar. He tends to lean based solely on fuel flow. Ray is considering going to dual electronic magnetos, but he's concerned about redundancy and the safety of the associated battery. The hosts talk at length about the benefits of dual e-mags, and think that redundancy is better with e-mags than traditional magnetos, so even though you're going away from two independent systems, it's still an improvement. Mike said the TSO for the battery containment is extremely high, and not to worry about thermal runaway. The company must also think so because apparently the experimental version is largely the same, minus the same battery containment. Eric is a new A&P and he's trying to become better informed on the difference between major and minor overhaul. He helped a friend create an external charging port for a battery minder on the belly through an inspection port. The hosts are wowed by the work, and want to do it themselves, and all agree it's a minor alteration. It doesn't stick out into the airflow any more than a GPS antenna, which is a minor alteration. Mike recommends reading FAR Part 1.1, which gives the definition of a major alteration. If it doesn't meet that definition, it's minor. But of course Eric is a scientist by day and doesn't love the ambiguity of the reg. Mike says it's in his best judgement, and part of his role as a mechanic. Walter is trying to track down an oil leak on his Beech Sierra. Over a few years he's had his mechanic address multiple trouble spots, and over time that's helped. But recently he's had some oil pooling on his lower cowling. Colleen thinks areas such as oil return lines are problematic. The rubber boots connecting those lines get worn out and can be replaced. She's been trying to track down an oil leak on her Lycoming without luck, and gives Walter a bunch of places to check.

Mike, Paul, and Colleen dig deep for some detailed troubleshooting on digital fuel indicators, oil temperature, gear problems, and more this episode. Send your questions to [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Will's fuel indicators are giving off infrequent red Xs on his Garmin G1000, and it started happening right after maintenance. Paul is suspect that a mechanic caused it, especially because you have to take the wings off to get at the sensors. But he's pleased at Will's level of troubleshooting, which includes info about what happens when the tanks is full, half full, and while turning on the ground. Based on the information, Paul is sure it's a sensor issue. On computer-based fuel indications, a mismatch between multiple sensors can often result in the EFD showing red Xs, he says. It turns out Will's mechanic was able to fix the problem by checking the connectors in the same inspection panel he had opened for the annual. Brad has a Cessna 182 that he keeps in a dry climate but is now flying to the Texas Gulf Coast a few times a month, where it sits for three days. He's wondering how to hold back corrosion. Paul suggests he wash the airplane when he gets home each time, and make sure the inside is fogged with Corrosion-X. Mike said not to worry too much about the engine because his single-weight oil and CamGuard will help protect it for those three days. Carl has a Cessna 210 and twice the landing gear motor didn't stop running when he cycled the gear. Paul then spends a few minutes describing the 210 gear system in great detail, including all the safety of wallet issues. The oil temp is high (235 degrees) on one of the engines on Ben's Twin Comanche. The hosts go through a slew of troubleshooting steps, most of which Ben has already performed. The hosts settle on this being an airflow issue, and not a fuel issue. Mike said the oil temp limit is an oil longevity concern, not an engine damage concern.

From maintaining aircraft records to dealing with bad advice and sub-standard parts, Mike, Paul, and Colleen say being an aircraft owner is one of the hardest jobs in aviation. Email your questions to [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Randy wants to know if circuit breakers have a life limit. He has a Mooney with about 3,000 hours. He had one that was acting up, and was wondering if he should intentionally exercise or change them on some interval. Paul said he recommends to all his clients that they exercise their breakers every few years, since they do tend to corrode. Just tripping it breaks oxidation off the contacts, he said. If you check the resistance before and after the resistance often goes down. Colleen said she replaces a few breakers during each annual.   Gary owns a Lake Amphibian with a IO-360 and he runs with fine wire plugs. At the last annual he found four of his Champion plugs had infinite resistance. They otherwise seemed to function normally. He’s wondering what the implications are? Paul said he has boxes old boxes of new Champion plugs that he can’t force himself to throw away, but he refuses to give them away either because he doesn’t trust them. The hosts said they’ve seen many problems with Champion fire wire plugs and the insulators. So they’ve stopped using them and suggest others do as well. They all endorse the massive electrode Champions are just fine, however.   Chris helps clients establish aircraft logbooks after they buy their first airplane. Paul said: You should keep as much of the maintenance records as possible for value. Old invoices he puts in a bag and sets them aside. He keeps weight and balance history and it’s nice to have a 337 record. Only the current equipment list is necessary. He’ll recommend customers organize their own logbooks and not pay him to do it. Colleen also keeps a separate spreadsheet for time in service of all the airplane’s components. That makes it easy for inspection, replacement, and for ADs. Mike’s records include a big Word doc that includes all his maintenance records and a spreadsheet with the weight and balance, equipment list, and so on. Paul suggests only giving your maintenance provider a thumb drive so they can’t hold your logbooks hostage, nor do anything else you don’t approve of. Then when you’re ready to leave, you get the thumb drive and the sticker to go in the logbook when you get home.   Paul read an article that advised against leaning too quickly and leading to washboarding of cylinders. Mike thinks that came from an old service bulletin. He said it needs to be taken in context. They were talking about heating the cylinder too fast. They weren’t talking about the transition from rich of peak to lean of peak, but rather a very rich mixture to a slightly less rich mixture. The piston heats faster than the cylinder barrel, and it expands faster than the cylinder. The piston could potentially cause metal to metal contact.

What's in our oil, how to keep cool (and warm), and lean of peak are on tap for this episode. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: Mark flies a 182 and he read on a forum that the reason we've had so much spalling of lifters is because they took zinc out of the oil. Mike said this rumor has been going around for years, but doesn't make sense considering zinc was never in aviation oil. It's in STP, which is used as a thread lube. He cautioned not to put that in the engine because it's not ashless. The problem with lifters has been poor manufacturing, Paul said. Bob has an RV-10 and he's been trying to run lean of peak with wide open throttle. His technique has been to reduce rpm to get to 55 or 60% power and then lean. But doing so puts him at around 2,000 rpm. He's worried that running it too low might result in problems. Mike gives Bob a better technique. He said the mixture controls power while lean of peak, although running at a lower rpm is generally better since the combustion event takes longer. By running a lower rpm you're giving the engine more time to burn through the available fuel/air mixture. The low rpm prohibition that Bob is worried about in other airplanes is usually the result of propeller resonance issues, they say. Jeremy wants to know when to plug in the pre-heater. Other pilots have told him he needs to plug it in 10 to 12 hours before flying, but he's checked the temperatures with his engine monitor and found they rise about 35 degrees above ambient in two hours. Paul cautions that the oil won't be that warm, only the metal at the CHT probe, but because Jeremy is running multi-weight oil it doesn't matter. Mike said his rule of thumb is generally to preheat when it gets below 32 degrees F, and that when the rocker covers no longer feel cold to the touch that you're done. In Jeremy's case they agree that two hours seems fine. Johann has a Cessna 210 that has a hot cylinder. He's gone over the baffling, which helped, but he's wondering what else to do. Paul tells Johann to throw fuel at the problem. He sets the fuel flow a half-gallon to one gallon over the book number, advising that you'll know you've done too much if it runs rough at takeoff. With Johann's intercooler, he recommends even more. Because intercoolers bring more dense air into the engine, you have to adjust the fuel flow, although the manufacturer doesn't say how much. So it takes some trial and error. Paul also advised Johann to look at his engine mounts and considering installing an aftermarket prop. On the 210 a tight tolerance between the spinner and the cowling can greatly reduce temperatures. If the spinner is low you can raise it with new mounts or spacers under the front mounts.

In this episode, Mike, Paul, and Colleen discuss unnecessary maintenance, lean of peak, and flaming exhausts! Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: Mitchell has a Cessna 185 and he's wondering if it's smart to change out the rotocoils on his engine at some pre-determined point in order to avoid uneven heat patterns on his exhaust valves. Paul, despite having done this, advises him to borescope, and only change when he sees an uneven heat pattern. Since Mitchell already borescopes often, Paul thinks he'll catch a faulty rotocoil quickly. Mike suggests that Mitchell could hit the coil with a mallet and if it doesn't turn to change it. Regardless of the test or monitoring method Mitchell chooses, they agree it's unnecessary to change the springs pre-emptively. Doug has some questions about lean of peak. Specifically, he's wondering why his EGT spread is so large when his GAMI spread is only .2 gallons an hour. The hosts remind him that EGT only matters as a way to identify peak. Otherwise the relative and absolute numbers are meaningless. The big gap in EGT and CHT numbers often comes down to cooling inefficiencies, according to Mike. If the numbers indicated that the cylinders were making differential power, Doug would feel the engine roughness. So the hosts think he's doing just fine. Adam wants to know if he can use an automotive alternator in his Cessna 172 under the new VARMA policy. The policy allows for part substitutions when no aviation parts are commercially available. Since 172 alternators are available, he must use one of those. The hosts then discuss what makes an aviation alternator different from an automotive version since Cessna and Piper use GM and Ford alternators. Paul and Colleen focus on the brushes, which are different, and ours turn the opposite direction, which would require a different pully. Although they agree an owner could bring an aviation alternator to an automotive rebuild shop with aviation parts, they recommend against a straight automotive version. Mark has a Cherokee 235 and he likes to take videos of his flights in order to critique his skills. One one night flight he saw flames coming out of his exhaust, which he obviously found alarming. The hosts put his mind at ease, telling him it's a natural by-product of the combustion process, and simply represents the power his engine is making. But they dig further to find out two important points. First, Mark doesn't have a flame cone on his exhaust. If he did, the flames probably wouldn't be visible. And two, this only happens when he's lean of peak. This intrigues Mike because it's evidence of a slower combustion process that's known to happen during lean of peak. He surmises that because the process is longer, but the rpm consistent, combustion isn't complete when the valve opens, which is why Mark only sees the flame.

Gotchas and head-scratchers are the theme this episode, as Mike, Paul, and Colleen help an owner with a pitted camshaft, an inop instrument, a faulty vacuum line, and ops procedures. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: Mike had two airplanes over the past 10 years with crankshaft pitting, despite regularly flying, hangaring, and using an engine dehydrator. He's wondering if there's anything else he can do to keep the rust away. The hosts focus on the timing of the events and consider that maybe Mike was caught up in a period when Continental had manufactured some sub-standard parts. They are confident Mike did the right thing by having his mechanic use the guidance in Continental's Service Information Directive 05-1B, which describes how to inspect and then when to replace the cam if spalding is found. Trevor has a Cessna 152 and he noticed that the vacuum line near the static sump had been bumped and was disconnected. It's a simple assembly that doesn't require tools to replace, only some teflon thread. He's wondering if that would be acceptable to do under the regulations for preventative maintenance. The hosts agree that it fits the definition of preventative maintenance perfectly, but that changing out the line would trigger the requirement for a static system leak-down test, which doesn't meet the definition. So, although a pilot could probably replace the line, he/she would have to hire a mechanic to do the leak-down test anyway. Brian is the manager of a flying club with a Cherokee that has a persistent inop flag on the S-Tec 30 turn coordinator, and he wants to know if you can label only the inop flag as inop. Mike thinks that's sound logic, but Paul and Colleen are a little more skeptical. When Brian says the airplane is used for checkrides, the hosts agree that DPEs are probably not going to allow it, and to placard the entire autopilot inop. Tim is wondering how many times to cycle the propeller during the run-up checks. The hosts all agree that once is sufficient, unless there's a need to do more. That might be because the oil is very cold, the hub is large, or there wasn't a good response on the first try. But all the parameters that need to be checked can be done in one pull, and a second and third pull are unnecessary and cause unneeded strain on the engine.

How do you fix a fix? Mike, Paul, and Colleen explore STC challenges, including parts, wrong installations, and ADS-B that isn't working. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org Full notes below: Barat has a Cirrus SR22 with an STC air conditioner. The driveshaft recently broke and he’s wondering how to fix it. Some mechanics he’s spoken to won’t use alternative parts, but others will. Mike said it’s not unlike altering the original type certificate. The question is whether your alternative to the supplemental type certificate is major or minor. Mike and Paul agree that it sounds like a minor alteration because the parts are now available from Cirrus, based on the STC that Barat had it installed previously.   Kevin has an LX7 with advanced avionics. A month or so after a trip through the Southwest, he got a letter from the FAA saying his ADS-B wasn’t functioning properly. He’s wondering how to know whether or not it’s working. Mike said he thinks this problem is similar to the transponder question. Even though there’s a reg that requires that an installed transponder be on and functioning, there’s no way to know if that’s the case, other than an ATC report or during a 24-month check. The hosts suggest you could do the same with ADS-B, requesting a report from the FAA on a periodic basis.   Byron has a Cessna 170 that he purchased three years ago. The airplane came with vortex generators that were installed incorrectly. Byron is wondering what he should do next in terms of holding the original installer accountable. The hosts caution him on going to the FAA because they can’t investigate halfway. Mike wonders whether the FAA would actually go after the mechanic, since it’s not a safety of flight issue. Paul thinks making an honest mistake is usually let off from the FAA with minor infractions.

Mike, Paul, and Colleen are in the hot seat as they answer live audience questions from Airventure 2025. We'll be back with our regular show next time. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join

How to tell the difference between greases? Mike, Paul, and Collen break it down, plus high lean of peak temps, breaking in an engine on an experimental, and composite airframe cracks. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: Mark wants to make sure he’s clear on which grease to use for which application. The manuals call for specific greases, but there are allowances for those with equivalent specs. But Mark wonders how to determine whether another grease is equivalent. Paul said you need to find the spec sheet for the grease the manufacturer recommends, and the spec sheet for the grease you’re thinking of using to make sure they more or less match. He also mentions Hartzell’s guidance that you can move up in grease numbers, but not down. Paul also cautions Cessna owners not to grease their flap tracks. They’re not meant to be greased, although the rollers are supposed to be lubricated. Grease Options March 24 2022, David Prizio, Kitplanes:  https://www.kitplanes.com/grease-options/#:~:text=If%20your%20plane%20lives%20on,05%20and%20GN%2015%2C%20respectively   For a full grease cross reference chart: EMTC https://emtc.aero/wp-content/uploads/2021/01/Mappe2.GREASE-XREF-1.pdf From the LPS product application guide: https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://pdf.directindustry.com/pdf/lps-laboratories/application-guide/11942-89226.html&ved=2ahUKEwjYgbmQiIiOAxVHHTQIHS21OzQQFnoECB4QAQ&usg=AOvVaw0KD4UOmbKMMo-0_4cGPymS Todd has a 2008 Cessna 400 that he just took delivery of. The airframe around the windscreen has a few little cracks that look like spider cracks. He’s read that there’s been an issue with this area and he’s wondering how much it matters. Paul said Todd is seeing cracks in the filler, and the expansion and contraction rate of it is different than the structure, which causes the cracks. Cessna apparently said back when it was built that they were working on a warranty repair for this area, but never did so.   David is wondering how to break in a new engine on a new experimental airplane he’s building. He has the engine now pickled, waiting for the airplane to be finished. Colleen did some research and on the Van’s forum someone posted a poll asking how people balanced engine break in. Some mentioned not doing the stalls on the initial flight, and they decided to prioritize the engine break in. Mike said high power ground runs are fine during break in. Low power or long idling can glaze the cylinders.   Jason is worried about his lean of peak temps on his B55 Baron. With the cowl flaps closed and a relatively warm day outside, he can’t keep one of his cylinders below 400 degrees. He’s done the Savvy flight test profile, and Savvy told him that the GAMI spread is acceptable and suggested checking the baffling. The first thing the hosts tell Jason to do is not compare the two engines. It’s irrelevant data. They focus on the baffling, even though Jason’s mechanic said it looks good. Paul said he’s seen cases where the baffling is wavy, which requires a slit be cut so that it lays flat and incoming air flow pushes it against the surface next to it (usually the cowling). After taking a deeper look, the hosts also suggest swapping probes to see what happens.

Mike, Paul, and Colleen explain why they almost never set their parking brakes. Plus, valve guide concerns and gotchas on preflight. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: William wants to know how Mike, Paul, and Colleen do preflight inspections as A&Ps, and if they look at something that most pilots don’t. Colleen said she always checks the last thing she worked on. She suggests to look really carefully at any work that’s recently been completed. Paul mentions the nut and cotter pin on the trim tabs on Cessnas, especially after maintenance. Mike said he worries if the airplane has been moved while on the ground for things like tow limits. Paul also said to check nests, pitot covers, and fuel vent covers for bugs, dirt daubers, etc.   Michael is wondering what’s wrong with his parking brake. When he first bought the airplane, the parking break worked to hold the airplane, but wouldn’t release without touching the brakes again. Now, after some work during annual, if it’s anything more than an idle, it won’t hold. Paul said he only ever sets the parking brake to get out and set the chocks. There are only two possibilities, the hosts say. IT’s either mechanically mis-rigged, where the valve isn’t cutting off the line completely, and the other is that the valve is leaking. Paul said the system is simple. You hold the brakes, and the valve pinches off the line.   Joey has a Cessna 150 and he does a lot of his own maintenance. About a year ago he had a stuck exhaust valve. A local mechanic did the rope trick to free the valve. He cleaned the exhaust valve guides, although not thoroughly enough. He had planned to do it every 300 hours. He and his wife were flying a few months later, got another stuck valve, and thankfully were able to make a safe emergency landing. He tries to fly very lean, but it happens so often he’s wondering what else he can do. Paul said to definitely ream all four cylinders. Joey is planning to do it every 300 hours at this point. But it takes a full day and he’d like to do it less. Unfortunately the hosts don’t see a way around it until he can run unleaded fuel. He might try a lead scavenger like TCP, they say.

Oil is everywhere this time, with consumption and temperatures problems for three of our owners. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Mark has a Twin Comanche and is loving his new electronic ignition. He has an issue where oil temperature and CHTs are slightly different on one engine than the other. His oil temperature also spiked on one climbout on a hot day, and he’s wondering what’s wrong. He’s using the variable timing. Nothing like this happened prior to the ignition install. Paul suggested that maybe some baffling changed during the install. The hosts narrow in on either airflow or oil flow as the culprit. Colleen said to think of baffling not as trying to direct airflow across the engine, but a system that creates a high pressure, pushing air through the cylinder cooling fins.     Chris is wondering what’s wrong with his new engine. He has a Cessna 206 and he put in a new Continental IO-550. After some initial runs, but found that it was burning about a quart of oil per four hours. On one flight is running a bit rough. It had turned out to be a failed magneto. They added an air/oil separator, which obviously didn’t help. He did some low level, high power runs that didn’t seem to help. At 100 hours he did a ring flush on Savvy’s recommendation. The ring flush seemed beneficial. Then after 10 hours he had only burned a quart. They are now at 150 hours and they are at a quart every 4 or 5 hours, and they’ve done another ring flush and it’s burning less oil again. He’s wondering why the rings are clogging up. Mike immediately zeros in on the problem by asking how long Chris has been running straight weight oil. He admits it was 150 hours on the advice of his mechanic. AD oil helps to prevent sludge build-up.   Willie is wondering if you need an A&P to do an AMOC, or alternative method of compliance with an AD. The hosts describe the process, which can be completed by any “operator” meaning owner. So, one need not hold an A&P to request an AMOC. Most AMOCs apply only to the operator, although Mike said a manufacturer can develop a global AMOC that would apply to everyone.   Steve was flying his Cessna 182RG with a Lycoming O-540 that he recently top overhauled with all new cylinders. He flew low and at high power to break them in, and oil consumption stabilized. He flew another 15 hours on regular oil and Camgard with virtually no oil burn. Then on a flight he was asked to slow rapidly on approach, and on that one flight he lost oil at a rate of three-quarters of a quart per hour. The consumption eventually settled at around a quart every 2.3 hours. He’s wondering if ring flutter is real and whether it caused the increased oil consumption. He didn’t notice excessive oil on the airplane. A ring wash didn’t fix it. He eventually decided to just overhaul the cylinders again. On inspection they didn’t find anything. Mike would have suspected a broken ring or expander spring. Paul wonders if the piston rings were wrong for the nickel cylinders Steve had installed. Unfortunately, he found a broken stud at 20 hours on his new cylinders. They hadn’t properly torqued 4 of the bolts on his cylinders, reinforcing Mike’s point that sometimes it’s better to leave cylinders in order to avoid maintenance induced failures.

A Cirrus with fluctuating fuel flow, de-injecting an engine, and fear of overhaul are on tap for this episode. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Joe has a Maule with a 540 engine in it. The company has a mod to turn the engine to a carbureted version and he’s wondering about the legality of something like that. Paul said it happens in the 210 market. Whether it’s a good idea is another issue, the hosts say. Joe is unable to run autofuel is the injected version, which is why he’s interested in it. Colleen said she’d rather have an injected engine than run mogas.   David wonders how perspective owners are so afraid of TBO. He has a 182 with an engine that’s nearly at TBO, and people who contact him are afraid of the high time. The hosts discuss strategies for buyers who may be looking at airplanes with engines at TBO. Assuming the engine is running well, a new owner can fly it on that “borrowed time” while they learn and enjoy the airplane. Alternatively, if the engine truly needs to be overhauled, the time down is obviously a concern for a new owner. Mike said he thinks it’s best to buy an airplane with a run-out engine. The price has been discounted for the cost of the engine, the seller is motivated, and worst case you have to overhaul it soon. And every hour and year that you don’t have to overhaul it is “free.” And when it does come time to do the overhaul, you get to do it to your spec.   Shalom has a Cirrus that isn’t behaving. If he sets the mixture at lean of peak, the fuel flows start to fluctuate. A few minutes later, it will drop off sharply, and then back quickly. The manifold pressure and rpm stay pretty consistent. He’s changed the fuel pump and the spider. Nothing has helped. Mike said if there’s a constriction in the fuel line between the fuel control unit and the manifold, it can cause oscillating fuel flow and lower flows.

An owner wants to fly his engine after it sat for 7 years. Plus, prop strike at the shop, lean of peak, and break-in trouble. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: Rupert is having trouble breaking in his new cylinders. They have five hours and the temperatures are still trying to go above 420 degrees on departure. They’ve checked fuel flow and baffling. In a twist of irony he is causing his cylinders to run too hot because the break-in is being prolonged because he won’t run the engine hard enough. Paul said Comanche’s have notoriously have poor baffling, which can also compound the problem. They recommend running it hard for a few hours and not to worry about the temps being around 420.   Craig has a Pitts that was damaged on a high-power run-up after his annual. The tail came up and hit the prop. He’s wondering if there’s something else they should inspect since the case is going to be open. His crank is subject to an AD. The associated service bulletin requires replacement if the case is opened, but the AD does not. He said the insurance has agreed to replace the crankshaft anyway. They said other than close cylinder inspections, it sounds like he’s fully covered.   Larry was finding that the lean of peak indication on his Dynon would show that he was lean of peak before the cylinders were actually there. He found a short paragraph in the manual that says if he changes the horsepower percent rating, it works fine. He also describes a procedure in the Dynon that basically recreates the GAMI lean test. Mike describes how Savvy does the AI engine modeling. The amount of air or fuel going into the engine will be the limiting power factor. In rich of peak, fuel is abundant, so air is the limiting factor. In lean of peak, fuel is the limiting factor.   Dave last ran his engine 7 years ago. He mixed oil and camgard, put it into a pressurized tank, and sprayed it under pressure into every place he could. He’s changed desiccant plugs, and had a dehumidifier running as well. If he has pitting he’s wondering if it’s dangerous to fly. Paul said airplanes don’t fall out of the sky because of pitting on the camshaft, and Mike added that they do fall out of the sky after taking off cylinders to look for signs of corrosion. Either the engine will make metal in the filter or it won’t, he said. If the filter is clean for the next 100 hours he dodged a bullet. Nothing that could be wrong corrosion wise is a safety of flight item. It’s a safety of wallet item. Paul said he would recommend changing the oil soon after running it. If the cylinders don’t look corroded the bottom end probably isn’t either, Mike said. Paul suggests he crank the engine with one set of plugs inoperative until he gets an oil pressure indication, and then start it normally.

Valves are sticking all over as the hosts give advice on how to avoid pulling cylinders. Send your questions to [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Rick has a 182 with a new Pponk engine and he’s burning lots of exhaust valves. He’s wondering what he should change operationally. Paul said to borescope more frequently to find the asymmetric burn patterns before they need to be replaced, and if they start to have asymmetric patterns to lap them immediately. He recommends borescoping every 100 hours. Mike gives some initial results of Savvy Aviation’s borescope initiative, which after 100,000 images found that 7 or 8 percent of valves showed signs of heat distress. Twenty five percent of the engines had at least one valve that was heat distressed. About 85 percent of those valves were in the early stage of distress and could be lapped. Only about 15 percent were considered late stage.   Brad has an SR22 with an IO-550 that had high oil usage. They pulled a cylinder, rehoned it and put on new rings. Later he started asking questions about torquing the through bolts, and the shop told him they held a wrench on the other side, but didn’t torque both sides. He’s wondering if he should go back and retorque the bolts. Mike and Paul think he’s probably ok.   Bruce is sick of sniffing gas fumes. They installed new fuel senders and a digital fuel gauge in their 172. They followed the procedure to calibrate the fuel senders, but he’s having trouble getting it correct. He’s as much as two gallons off from what it should be. Paul starts by asking what bucket Bruce is using because the utility buckets from the home stores are unreliable as calibrated containers, he said. The other issue is the wet wing construction, which can lead to dams that make it difficult to fully defuel or refuel. Bruce has even accounted for temperature. He’s within half a gallon on one side, which Paul said is usually as close as you can get it. Ed is stirring the pot. He read that in an article in the American Bonanza Society publication that operating lean of peak is bad for engines. Obviously the hosts disagree, and a discussion of the merits of rich of peak and lean of peak ensues.

It's all engines all the time this episode. Rusty ones, sticky ones, and one that doesn't burn oil. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: Ralph had to throw away his relatively new engine. His flying club has a 1968 Cherokee 180. They overhauled their engine, and the first annual looked good. On the second annual and after only 100 hours of flying, they had a stuck valve. Digging in they found extensive corrosion. Now past a second overhaul, they want to ensure it doesn’t happen again. The hosts focus on how much (or little) the airplane flew with the new engine. 50 hours a year isn’t much, especially if they weren’t regular hours. An hour a week is great, for example, and something like 4 hours once a month is worse. They advise Ralph use camgard, fly more often, hangar it, and use an engine dehydrator.   Adam has a Cirrus SR20 on leaseback to a flight school with only 500 hours on it. A student was taking off, and around 900 feet they heard a bang, and experienced partial power and a loss of oil pressure. Lycoming took the engine back for an inspection. Sticking valves caused it to throw a rod. Mike said Lycomings often stick valves, and it’s something that should be expected. The manufacturer recommends a wobble test per Lycoming Service Bulletin 388C every 400 hours in airplanes and 300 hours in a helicopter. You can go a thousand hours with the new valve guides. Mike stressed that it’s also very important to be trained to detect morning sickness, which is usually the first sign of a valve sticking problem. If a cylinder doesn’t light up with the others on a cold start, or feel rough, it indicates valve sticking and the engine should be shut down right away and examined by a mechanic. Colleen suggests having an eagle eye on the engine monitor during the first startup of the morning. Mike said leaning aggressively, especially on the ground, can also help. Adam asks if Lycoming’s recommendation to run the engine up before shut down in order to clean the valves actually does so. Mike thinks it’s just inconsiderate of those around you, and maybe not terribly helpful.   Jason runs mogas on his Cessna 182. Last year he was climbing through about 8,000 feet and the engine started to stumble. He added carb heat and a few other things, but the engine seemed to come back to life on its own. His Savvy account manager said it was probably vapor lock. Mike agrees with the account manager that the airplane was exhibiting vapor lock symptoms. He thinks it’s possible that a fuel line might be close to the exhaust or something else is warming the fuel before it gets to the carb. Paul suspects it might be the fuel line to the JPI engine monitor transducer. They recommend wrapping it the fuel lines in fire sleeve to see if that improves the problem.   Thad has a 1977 Cessna 182Q. He had the engine rebuilt in 2021 and since then it has been “a rockstar.” He thinks it might burn too little oil. It’s only burning about a quart every 50 hours. It makes more chromium and aluminum than the lab is happy with. He wonders if the lack of fresh oil is somehow concentrating the contaminants. It’s possible he’s not getting enough lubrication on the cylinders, Mike said. The chromium can only come from the rings and the valve stems. Usually the problems with the valve stems come combined with increased nickel because they are made of an alloy. Mike said the aluminum in his report is ok, although slightly high. Thad said they’ve borescoped the cylinders and everything looks good. There’s still cross-hatching on the cylinder walls. The hosts are intrigued, but Mike thinks it’s faulty thinking. They debate how much metal stays in suspension though the process of adding quarts. Mike suggests keeping an eye on the filter, but otherwise to keep flying.

Chris is trying to make sense of his logbooks. He has a Cessna 172 RG and he and his partners had a few electrical issues recently. Some of the logbook entries went in the airframe book and some went in the engine logbook, and he’s wondering about the decision-making process involved in picking the proper logbook. Mike said there’s no requirements around which entry to put in which logbook, and in fact, there’s no requirement to have a logbook in the first place. It’s easier and retains the value of the aircraft, of course, but the need to keep a specific logbook isn’t based on regulation. The reason we use different logbooks, he said, is because if we were ever to sell the engine separately from the airplane, it would be nice to be able to include the record in the sale. If the item would move with the engine, put it in the engine logbook. Paul said his shop only puts the annual inspection in one logbook, and typically that’s in the airframe book. Brandon has a 1977 Cessna 182Q with a low-time engine. Every time he borescopes it he sees lots of lead buildup on the valve stems of the cooler cylinders. He’s wondering if there’s a way to run it hotter, or is there something he can add to the fuel. The hosts agree that it’s actually a mixture distribution issue, something normal and expected in the O-470. Paul had a 182 and he did a bunch of lean testing. When he would lean to roughness and roll it back only enough to smooth out the engine, he would have two cylinders lean of peak, two at peak, and two rich of peak. Mike suggests adding TCP to the fuel. The main downside is that it’s quite toxic, so careful handling is required. Scott is interested in pushing the boundaries of the maintenance regulations. He’s wondering if he is allowed to sign off an AD as an owner because the regs don’t specifically state it has to be a mechanic. Mike thinks it must be an A&P because they are inspections, and only A&Ps can do inspections. There are a few ADs that explicitly allow the owner/operator to perform them. Paul suggests that a lot of ADs require a maintenance action that is outside the scope of owner-performed maintenance as well. Mike is questioning Continental’s guidance that limits extended running below 2,300 rpm. He finds that his airplane runs smoothest at 2,100 rpm. Mike explains that the bulletin came about after an issue with Cape Air and their 402s. After a few in-flight engine failures, they grounded the fleet and started inspecting engines. The failures were caused by counterweight release with accelerated wear in the pins and bushings. Continental couldn’t find anything wrong with the parts, and they guessed that it was due to operation at low rpm. Cape Air was operating at high power, rich of peak. They never tracked down the real problem, and guessed this was the issue. Cape Air had gone from operating at 2,300 rpm to 2,200 rpm. Mike believes that if you are operating at high power and rich of peak, it might be worth observing the limit, but if you are operating at low power, or lean of peak, you can ignore it.

John is a maintenance officer in a club, and he is wondering about tire ply ratings. The manual calls for 4 ply, but they often install 6 ply and he’s wondering if that’s ok. The hosts all agree that they have subbed in higher ply ratings when supply dictates. Paul’s rule of thumb is that he always allows a higher ply, but not lower. That’s because the ply rating relates to the weight of the aircraft. Heavier aircraft need higher ply ratings. They get into a discussion on retreads, which can cause issues. They like retreads, but caution that you must ensure they will fit in the wheel well on a retract. Paul worked on a 210 once that caught the skins when retracted.   Doug instructs in Aerostars, and he has worked with a number of clients lately who want him to omit the engine-out portion of the training in order to avoid stress on the engines. There’s talk in the Aerostar community about heavy and light cases. Mike said not to worry about the case. Rather, cylinders that rapidly cool are the concern and that’s because the piston and cylinder are different metal densities and cool at different rates, which can lead to scuffing. They all agree the training is important, but pulling the power back slowly, rather than cutting the fuel, will help reduce the risk of engine damage. Paul makes the point that flight schools do this in Seminoles all day, and that he doesn’t hear of widespread issues. Failure isn’t a concern, Mike said. Scuffing is a wear issue. If it’s an issue, Paul said his pistons probably look terrible, but he’s not going to worry about it. He already borescopes regularly. And Mike said he will run an aux tank dry on a long flight.   Jason has a Comanche 250 with some electrical issues. Throughout the flight the bus voltage will come down. After landing and taxiing in the voltage climbs back up, and rests around 13.8. Recently after takeoff, the low voltage alarm flashed and went to 10.8 while raising the gear. The hosts think it’s a voltage regulator issue, where it works when cold but not warm. Paul said he thinks of voltage as an indicator of whether the system is working and the amps as an indicator of how hard it’s working. It should be around 13.8 or 14 when working properly. Colleen said she had an electrical issue where her JPI would go offline when she would cycle the gear. Under the panel she found that there was a loose connection on the shunt, causing high resistance. Jason’s issue could be at the circuit breakers, voltage bus, voltage regulator, or any number of places. One way to easily troubleshoot is to see if he can find anything hot by running his hands along the wires. Or look for discoloration, Paul said.   Steve writes in asking about oil coolers. During his recent engine overhaul the shop asked if he wanted a congealing or non-congealing oil cooler. Congealing is bad, he thought, so he elected to go with non-congealing. But he lives in Arizona and he’s found the engine runs a bit hotter with a higher oil temperature in long climbs. He’s wondering if he made a mistake. Non-congealing oil coolers have a solid line running through the middle that passes warm oil through the cooler at all times. Mike thinks it’s possible the non-congealing has less cooling capacity because it has less surface area.

Should you trade your aging airplane in anticipation of higher repair costs on your current bird? Mike, Paul, and Colleen have a strong opinion on this. Plus, sticky valves, taking good care of turbos, and engine monitor set-up frustrations. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Scott has a Tecnam P2010 with a Lycoming IO-390. He’s had a few instances where cylinders dropped off, the engine ran rough, and then they quickly came back on. It was followed by morning sickness. In essence he had a sticky valve. He found that his CHT temperatures were quite low. At altitude, running the airplane at best cruise power, his CHTs are about 350 degrees. In climb if he leans he can get three cylinders over 350. Mike said he wouldn’t stress about the CHTs, but he would borescope the cylinders to verify that there isn’t too much build-up.   Yuriy has a new-to-him 2010 Cirrus SR22 that’s turbonormalized and he’s looking for some tips on taking care of his turbos. He flies lean of peak at 28 inches. He is limiting turbine inlet temperatures at 1,500 degrees. Mike thinks 1,500 is excessively conservative. The red line is 1,650 degrees, and Mike tries to keep his at or below 1,600 degrees. He also doesn’t subscribe to the one inch per minute reduction of manifold pressure. Lycoming at one time published a document that said not to cool CHT more than 60 degrees a minute. Mike’s engine monitor alarm is at 30 degrees a minute, and he said it doesn’t go off very often. He also doesn’t cool the turbo on the ground before shutting down unless he had high power right before landing for some reason.   Wade has a Cessna 185 with an IO-550. On his last annual he had a few burned exhaust valves. He’s trying to avoid higher maintenance bills in the future. Paul tries to make Wade feel better by telling him that burned valves have nothing to do with how he’s operating the engine and everything to do with the lead in avgas. Going through his operating technique, the only suggestion they have is for Wade to lean much faster, and avoid using the lean find feature. The green arc on his manifold pressure gauge is also wrong. He was worried that he’d have to take off at partial power in order to stay in the green arc on the gauge. The hosts discuss how to reprogram the display.   Matt doesn’t want to throw good money after bad. He’s wondering how long you should hang on to an airplane as it ages. He has a 1977 Cessna T210. Parts are starting to get scarce. It’s hard to find qualified mechanics. He feels like he wants a great airplane that lasts him well into the future. The hosts all agree that it’s better to hold on to the airplane he knows, and not to worry about 210 parts availability, at least when compared to other airplanes. 

Ever wonder how the flap system in a Cessna works? This episode Mike, Paul, and Colleen take a deep dive on the system, plus engine vibrations, leaning for high altitude takeoffs and go arounds, and getting bees out of a restoration. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Ken is experiencing vibrations in his Cherokee at certain throttle settings. After installing an engine monitor he discovered that with the throttle at roughly 90 percent full he could induce the vibration, but then quell it by using the mixture. He could see that a cylinder was going offline at full rich, but came back online when leaned. Mike suggests that he needs to lean in the climb to compensate for the overly rich mixture, but Ken said he’s also able to stop the vibration by reducing the throttle setting but keeping the mixture full rich. The hosts still think he’s too rich. They recommend leaning in the climb and keeping the EGT constant as he climbs. Ken also noticed that the cylinder that goes offline is also an outlier on the engine monitor. They tell him to do a GAMI lean test and an induction leak test to try and isolate whether he has a problem or just a poor mixture distribution. Find the test Mike described on Youtube: https://youtu.be/_VfiPuheeGw For more on the induction leak test Paul described: https://www.savvyaviation.com/wp-content/uploads/savvy_pdf/Savvy-Flight-Test-Profile-Expanded.pdf Marcus has a first generation Cirrus and he wants to ensure he is leaning properly for high-altitude takeoffs. Paul said to put his EGT around 1,300 or 1,350 degrees, which will put him close to the Cirrus chart, but is more accurate. For high altitude go arounds, Paul knows his fuel flow at around 1,300 degrees EGT, so he just sets the fuel flow to the expected amount. Luke has been having an issue with the flaps coming down in his 182. What follows is a loooooonnng and detailed description of the Cessna flap system. Blythe was restoring his family’s Cessna 150 and found a bunch of mud daubers. The inspection panels allowed him to clean out some, but he assumes there are more that he couldn’t reach. Paul said the potential corrosion is a key to the solution. He said the bees don’t like to build nests on corrosion inhibitors. He also said to make sure to check up the vertical stabilizer, which is a popular spot. Mike said he’s had luck with moth balls in other machinery. 

Can one high oil pressure reading forever alter your engine? Mike, Paul, and Colleen answer this question, plus the quirks of the O-470, compression test redemption, and repairman certificates. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Everett is wondering if his oil pressure is forever altered. He has a Piper Colt with an O-235. The pressure used to be 75 psi, and on a flight the oil temp spiked and the pressured went up to 85 psi. Even after cylinder work, the temperature and pressure have remained high. Paul starts by asking if he’s sure the indications are correct. They suspect a blockage somewhere, although there’s no oil cooler on the O-235. They suggest getting a manual to check for the engine’s entire oil pathway and follow it to see if he can find a blockage. Randall wants to know if the hosts are too hard on compression tests. He asks whether they hold any value. Mike said there’s no harm in doing compression tests, but that one should never change or overhaul a cylinder with compression numbers alone. Knowing where the air is escaping does offer some value, they say. There’s not much you can discover on a compression test that you wouldn’t discover on a borescope inspection that impacts safety of flight, Paul said. Manuel asks how EGT and fuel flow relate on his Cessna 180. He’s seeing a spike in EGTs before they come down again on takeoff. The low compression O-470 will have higher EGTs, especially on takeoff. Mike said Manuel's engine monitor is configured for a carbureted engine, and thus puts a big time delay and smoothing function on the fuel flow. Without the smoothing, the fuel flow would wobble up and down often, making it hard to read. That’s why fuel flow indications rise so slowly after adding takeoff power. And bu slowly adding power, Manuel is delaying the addition of the enrichment function of the carb, which is why he’s seeing a delay for the EGTs coming down. Marty is trying to understand repairman certification limitations. He’s done some work on his prop, magnetos, and so on, and he wants to make sure it’s all been legal. Mike said as he understands it, you basically have unlimited authority to do what you want on your airplane. The common sense rule applies, which is to get a demo or some instruction before you do it for the first time. 

Should you overhaul an engine based on oil analysis? The hosts answer this question, plus fuel pumps, valve grinding, and a pesky hot cylinder. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: David is worried about the relatively new IO-470 in his Bonanza. His oil analysis history shows a lot of aluminum, and recently, high on all metals. The narrative said to check for crankcase fretting. Paul said he would check the torque on the through bolts for piece of mind. Mike said he’s not particularly concerned about any of the numbers on the report. He said oil analysis is only a trend monitoring system. Once you establish a baseline you look for major diversions from the report. Colleen disagrees and said they aren’t stable, but have been increasing. There’s nothing that would cause all numbers to go up unless there’s dirt or a bad sample. Paul then details how David can use his borescope to look at the cam, a few lobes, lifters, and so on. It might not give him any information, but it could give him some reassurance that things are ok. Colleen suggests inspecting the pick-up screen if he can. Mike said he would never tear down an engine based on an oil report. Maurice wants to know about the fuel pump on his Mooney M20J with a Continental IO-550. He has an altitude compensating fuel pump, and he wants to know how to use it. Mike explains that it automatically leans for you in the climb. Once he’s ready to lean in cruise, it’s time to lean manually. Jared is ready to start grinding some valves. As he gets deeper into lapping valves in place, he’s wondering what sort of threats there are. Is it maintenance to the extent of being subjected to potential maintenance induced failures? Is it better to wait until a valve needs it, or could it be done pre-emptively? Mike said he wouldn’t necessarily do it pre-emptively, but if he sees any sort of potential deposits then it can be worth doing it. Paul said they go through an inspection process afterwards, including making sure the grinding compound is cleaned up as well as possible, that the valve keeper is properly in place, and that the bolts holding the rocker shaft holds are torqued properly. Paul said it’s critical to get another set of eyes and not check yourself. The hosts haven’t heard of any failures from lapping. Chris has an O-540 in his Cherokee 6 that was recently overhauled. His number 6 cylinder spikes up to 450 degrees CHT on takeoff and he can’t figure out why. Mike looked at his data going back before the current engine and found that even the old engine had high temps on number 6. Chris finds that the cylinder also run the leanest. Paul suggests it could be an induction leak. 

A 182 mysteriously losses power and the hosts struggle to explain why. Plus, basic engine temperature theory, confusing ADs, and why it's so hard to find good help these days. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Andrey was flying low and slow on autopilot for a mission when he noticed the airspeed dropping. He saw a drop in rpm, and an increase in manifold pressure. He also saw very low oil pressure. He added power, climbed, and returned to the airport. After landing, he checked the oil level and everything was fine. On a run-up check after talking to his mechanic, the engine stumbled. A new oil pressure sensor seemed to have fixed the issue, but he’s wondering if that’s really what was wrong. The hosts agree that it sounds like Andrey was having two issues because a drop in oil pressure shouldn’t impact engine performance. A big drop, or complete loss, will impact the prop governor, but not in the way Andrey experienced. After looking at the data they wonder if there was also something working through the oil pressure relief valve. Willie has a Cessna 310T and is confused about the exhaust AD. He’s getting conflicting information from mechanics and 310 experts. Mike was involved in the fight surrounding this AD, which is so confusing that the FAA had to issue an SAIB after the AD to explain it further. Yet the community is still confused, with the top Twin Cessna shops divided on when the AD should be complied with. Mike said it’s his opinion that it happen at overhaul. Others believe it’s 12 years. Andy is a maintenance manager and wants to know how to teach troubleshooting skills. Paul said in his experience techs can troubleshoot in their heads, do it via manuals and diagrams, or not do it at all. The process should not be, let’s go change this part and see what happens, he said. It should be, let’s go test something and see what we learn from the result. Relatively few mechanics are talented diagnosticians, Mike says. It requires a different skill set. Mike discusses Savvy Aviation’s new mechanic troubleshooting service they are working on. Royce wants to know if power equals risk. For example, if you have a higher compression engine or a turbo engine that produces more heat, will that impact EGT? Are peaks different based on the engine? Mike said CHT is basically measuring how much heat is present during the power stroke, while the EGT is measuring how much energy is being wasted out the back door. Paul said you can see this with an in-flight mag check when EGT goes up and CHT goes down. Running on only one plug shows how it’s more wasteful. Compression ratio is the big determining factor in the level of peak EGT. A higher compression engine will waste less heat, and thus have lower EGTs. 

Can you have a prop strike without a prop? This is one of the more unusual questions the hosts have faced. They also track down a carbon monoxide leak, advise on Continental rpm settings, and help an owner who likely had a pre-ignition event. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Robert is an A&P who is trying to help a flight school track down a carbon monoxide leak in a Cherokee. An instructor had a carbon monoxide event, took up a monitor, and found that it was reading at least 300 ppm. The exhaust and heater shroud were replaced, but the cabin was still getting more than 10 ppm. He’s wondering if there is a maximum level allowed in aircraft. Mike said Car 3 didn’t have a maximum, but that Part 23 says 50 ppm is the allowed maximum under current regulations. Hypoxia and carbon monoxide are cumulative, and he said his current comfort is below 20 ppm. He also said leaning impacts CO levels. Peak or lean of peak EGT lowers CO. How it gets in is a bit of a mystery sometimes. He said there was a case where Mooneys with air conditioning were drawing in air from the intake on the side of the airplane. Paul said in a Cherokee it comes in via the forward wing attach point. There is supposed to be insulation to stop it from coming into this area, but over time they are taken out or lost. It’s often not from the engine compartment. It’s through the belly or downstream from the exhaust pipe. John wonders if you can have a prop strike without a prop on the engine. He bought an RV9 with the engine on, but no propeller. He loaded it into the back of a box truck. Stopping partway to check on it, he found the tie-down straps had slipped and the airplane had be banging around in the truck. He’s wondering if he should be concerned, and what he should be checking for. Paul said to put a dial indicator on it and check to make sure it’s less than .005. Some of the bolts on the Van’s prop simulator were lose, and one was hard to screw back in. Paul said he would be surprised if there was any damage. Jesse has a 310 with Continental engines and he’s wondering about the service bulletin that recommends maintaining 2300 RPM in cruise. Previously the hosts said it’s probably good advice when rich of peak, but you could ignore it lean of peak. He wonders if he should go lean of peak first, and then pull the prop back, or is going to a lower rpm first ok? Mike thinks it’s sufficiently brief that it won’t make a difference. Rick had an infant mortality issue with his Mooney. His A&P found valve wear, oil though the rings, and corrosion on the engine, which only had a few hundred hours. He did a top overhaul, flew for 27 hours with the propre break-in procedure. About 30 hours later he got a high CHT indication on a descent, followed by dropping oil pressure. The belly was coated with oil and only 2.5 quarts were left. They found broken rings on 3 of the cylinders. They took off the electronic ignition, but are looking for ideas as to what may have happened. Mike found Rick’s data, which showed the CHT event was in cylinder #1, and the temperature rose at around .7 degrees per second. That approaches Savvy’s rule of thumb that anything at a rate of a degree per second or higher is a pre-ignition event. The hosts think it's possible the electronic ignition was the culprit. He thinks the broken rings may be an unrelated event. Colleen said improper ring installation could have caused the new ones to break She also suggests checking to make sure he doesn’t have a cracked plug. 

How to identify CamGuard in an oil analysis, erratic idles, how to check the oil, and what the wrong prop does to an engine are on tap for the latest episode. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Tan has a 1968 Piper Arrow 180. He has an erratic idle as the engine warms. Mike and Paul said it sounds like maybe sticky valves. He and his mechanic haven’t done the wobble test. It almost can’t be a spark plug, Mike said. Colleen said it could be an ignition harness. Paul suggest he could do an in-flight mag check to help verify. Even though it should start with morning sickness, Paul said it’s not unlikely that it’s a sticky valve. Fuel could also be an issue, as they’ve cleaned the injectors, which Mike, Paul, and Colleen think they induces more problems than it solves. Dicky is concerned about his last oil analysis report. Some of his wear metals are much higher since he’s been using CamGuard, and he’s wondering whether that’s normal. High calcium and high phosphorus are CamGuard’s signatures on an oil analysis, according to Mike. One thing Mike noticed that Dicky didn’t ask about was high silica, indicating dirt in the engine. High silica usually brings high wear metals because the dirt acts to scrub the cylinders. Dicky said he had a problem with his air filter box, and had replaced a part. Enock is trying to settle a flight school debate. He checked the oil and the instructor asked if he screwed the dipstick back in when checking it, or if he just tapped the stick to the top of the tube. Everyone he asked at the school had a different answer. Paul said he screws it back in to check. Colleen agrees. Mike said all the readings should be taken with a grain of salt. He recommends running about two-thirds full. Many type certificate data sheets have a minimum level. And the only somewhat accurate reading is the first one of the day when the oil has time to fully drain back into the sump. Rex is doing his best to follow the hosts’ leaning guidance. He has an RV-8 with an IO-360 engine with high compression pistons and e-mags and a fixed pitch propeller. He isn’t able to lean full throttle, but he can at cruise power. Mike clarifies that the guidance to leave the throttle full forward was for constant-speed propellers. Operating lean of peak slows the combustion event. The flame front takes longer to propagate. Engines don’t like lean of peak if the rpm is too high because the faster speed of the engine doesn’t like the disparity. Mike said he lowers rpm while keeping the throttle full before he leans. Then Rex makes an off-handed comment about his prop pitch, which the hosts quickly pick up on. They are convinced he has the wrong prop. He’s only getting 2400 rpm at full power in cruise. He also had a denotation event, and is trying to determine what the normal timing is supposed to be.

Clogged injectors, how to care for an engine while training, avoiding costly altimeter checks, and engine design considerations are on tap for this episode. Email [email protected] for a chance to be on the show. Join AOPA to become a member of the world's largest aviation community at aopa.org/join Full notes below: Marko’s engine had a strong revving sound on takeoff. He saw that he had an EGT above 1,800 degrees and one that was below baseline. A run-up after landing made it seem like it one cylinder wasn’t firing. A borescope inspection revealed nothing unusual. A subsequent check of the injectors found that there was debris in one. His mechanic suggested it was a blocked injector. He’s wondering what would cause that. It turns out this event was soon after the annual when the injectors were cleaned. The hosts agree that the maintenance is clearly what caused the clogged injector. Mike said this is such a delicate operation that he thinks it’s almost as if the fuel system should only be cleaned under sterile conditions. Colleen said she used to clean hers, but now doesn’t because she knows the risks. Paul colorfully describes the problem of cross-contamination. Dylan teaches in a carbureted Seminole and he wants to treat the engines well, and is looking for best practices. He mentions shock cooling, which the hosts quickly debunk. The school’s engines are over TBO and they’ve never had to replace a cylinder. Obviously whatever the school is doing is working. He’s also wondering about failing the engines. Lycoming recommends failing the engine with mixture, but many people like to shut off the fuel. Mike said he wouldn’t worry about shutting the engine down from the fuel selector, and that it shouldn’t introduce air or other issues. Mike worked in the auto industry for many years, and he works on his own airplanes as much as possible. He’s wondering why aircraft engines don’t have ventilated crankcases. Mike said crankcase ventilation is primarily for environmental reasons. And piston aircraft engines have significantly more blowby. You don’t want to keep it in the crankcase. He said air/oil separators return a lot of junk back with the oil. You want the filth to leave as much as possible. Doug has three altimeters in his airplane, and he’s wondering how to save money on the checks. Mike thinks he shouldn’t be charged three times for three checks because you hook up the equipment once, and adding on a second or third altimeter doesn’t take too much additional time. Each check includes about five tests, according to Paul, and each has to be separately documented. 

Mike, Paul, and Colleen sludge through oil pumps that lose prime, skipping an oil filter change, and using the right oil in this Texas tea-themed episode. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org Full notes below: Mike has a Cessna Bird Dog with an oil pump that isn’t cooperating. When he lets the airplane sit for a month or more, he doesn’t have oil pressure on the first start up. He’s conceived a workaround of pumping oil by hand into the engine and turning the prop backwards. Paul and Mike both describe having experienced this issue with Continentals. Mike said that Continental told him to prime the pump by removing the top spark plugs and pressurizing the case with shop air while you move the starter. Paul said they will unscrew the oil filter, fill it with oil, and then put it back on. Cameron is trying to protect the Aeronca that’s been in his family for decades. He thinks using thinner oil sounds good because its viscosity helps after not starting for a long time, but the thicker W100 might better protect? He flies mostly in the winter, but he preheats. Mike thinks his strategy to use W100 when it’s warm and multiweight is good for colder temps. Paul likes multiviscocity so he doesn’t have to worry about temperatures. Chuck is an A&P with another job, and he’s considering maintenance side hustles. He’s thinking of offering aircraft weighing services. He can either defuel aircraft or completely fill the tanks prior to going on the scales. Advisory circular 43-13 is unclear about which approach is better. Paul has always thought it strange that proper weighing procedures are in the POH, and not the service manual. That’s the first place to check, and the procedure that should be followed first. If there’s no procedure you go to the AC. He finds that most airplanes must be de-fueled first. Mike says to use FAR 43.13(a), which says that the mechanic must use the procedures in the maintenance manual, or acceptable practices and techniques. The AC has a note at the beginning saying that it’s only to be used if the manufacturer doesn’t have a process. But given that the procedure is in the POH, and not the maintenance manual, Mike suggests Chuck can pick and choose the way he weighs the airplane. Jared is looking for a more permanent oil filter solution. First he wonders if he can skip changing the filter when changing the oil, in part because they were hard to get at one point. Paul said the only time it’s required to change the filter is during annual, when the IA is required to inspect it. Mike said he would like to inspect the filter as often as possible. He considers it the most important thing to do to monitor engine condition. Although people have taken their filters beyond 100 hours, there is oil analysis data showing that it’s a bad idea. The hosts then discuss reusable oil filters. Mike changed to reusable filters prior to Oshkosh, and has been initially pleased with the results. The Challenger filter comes off, the filter element comes out of the can, and the filter then washed. He was astonished by what came out of the filter because it’s easier to see what comes out after washing versus having to see what’s in the pleats of a filter.

Lean of peak is causing odd vibrations in a Commander, and the hosts discuss proper troubleshooting. Plus carb heat on the ground, dehydrators, and parts no longer manufactured. Email [email protected] for a chance to get on the show. Full notes below. Chip said his mechanic is concerned about lean of peak because we don’t know the actual temperature at the valve, as the temperature is taken downstream. Colleen makes the point that EGT temperatures are fine because it’s well below the valve limit temperature. Mike said valves burn only when they don’t seat properly. They shed their heat through physical contact with the seat at the cylinder head. They also shed it through the valve stem. Detonation once flying lean of peak isn’t a concern. It’s getting to that point that’s the biggest risk. Paul suggests that once you know the fuel flow at your desired power setting you can lean straight to that fuel flow and not worry about EGT or CHT until it’s set and stable. Chip is also concerned about a vibration in the floor of his Rockwell Commander. Mike suggests he do some testing to help isolate the issue. If it goes away at certain rpms, then it suggests that it’s an engine-based issue. At a constant rpm but with changing pitch, it suggests a potential airflow or airframe source. Frank is questioning the logic of the Luscombe handbook. It says to put the carb heat on for takeoff. It’s also placarded that way on the panel. The hosts can’t figure out why this would be required. The hosts suggest he ignore the handbook and operate as he would in other airplanes, in part because the engine would be breathing unfiltered air while on the ground. Bill has a Cessna 180 on floats with an O-470-50 engine. For the last few months he hasn’t been flying as much and he wants to preserve the longevity of the engine. He is looking for details on engine dehydrators and whether they actually work. Colleen looked through some research and found that those who had done some side-by-side testing had found good results. Mike said Tanis found that people who ran their heaters all the time were causing corrosion, but that if they use engine dehydrators they are fine to run the heater all the time. In other words, they seem to work. Mark is pushing back on airport naysayers that tell him autofuel is dangerous. He flies airplanes with older, small Continentals, and with all the info that has come out on the transition away from 100LL, he’s wondering if he should be worried. Mike said running on autofuel is the best thing he can do for his engine. People tell Mark he has to run at least half low lead. Mike said they’ve never seen issues with low compression engines running on autofuel. Mark flies from an airport a mile high, and locals are also telling him that vapor lock is also an issue. 

Rough idle, electronic ignition basics, airplanes to avoid (or not), and the difference between detonation and pre-ignition are on tap for this episode. Email us at [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Stephen wants to get the engine on his Cessna 206 purring. At idle the engine stumbles down to 600 rpm. It never quits, but doesn’t run smoothly either. Mike asks if they’ve done an rpm rise test at 600 rpm. Paul explains it’s part of the installation process of a new engine. You set the engine at a set rpm, then pull the mixture back slowly to get a 25 rpm rise. More than 25 rpm means it’s running rich. Less than 25 rpm means it’s running lean. Engines don’t come out of a crate ready to go. They need to be set up properly. Mike also said that landing with full mixture rich is an issue as well. He said there are only two times you should have full mixture. One is when starting cold, and the other is when applying 100 percent power (at lower density altitudes). Mark is interested in electronic ignition for his 210, particularly the Surefly. Paul loves the Surefly on his airplane. He doesn’t love the advanced variable timing. He thinks a bit aggressive. But it is selectable, so you can turn it off if you like. Mike said he would try it with the variable timing on, and only turn it off if the CHTs are too high. Colleen said her husband has done the dual Surefly on his Legacy. He has higher CHTs, but not unacceptably high. The fuel burn is also lower, but the biggest benefit is easier starting. Erick is looking for any angle to justify buying his first love, a Cessna 337. He would prefer a turbocharged Skymaster. He’s wondering if there’s any hope for the future of these engines being affordable. You must go and buy a turbocharged Skymaster, Mike said. The engines that Mike has previously been worried about are on the pressurized Skymaster. The turbocharged engines are rated at 210 horsepower, and the pressurized ones are rated at 225 horsepower, which he thinks impacts longevity. He thinks engine longevity is related to horsepower per cubic inch. An O-470 is about .5 horsepower pre cubic inch. The TSIO-360 is around .625 horsepower per cubic inch. Warren is wondering if detonation caused a power failure in an accident he’s studied. The NTSB data shows that the cylinder reached about 700 degrees, and it went up by about 1.3 F degrees per second. Mike said CHT increases greater than 1 degree per second can only be caused by a pre-ignition event. It means that something in the cylinder was either acting like a glow plug, or if there’s a magneto failure. A cracked spark plug insulator can act like a glow plug, for example.

How do you know when to replace certain parts? They begin to talk to you. Find out what, why, how, and when when Mike, Paul, and Colleen tackle this and other questions. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: John is part of a club that owns a Cessna 172. Another member told him he shouldn’t move the rudder by hand when he preflights. Mike said to make sure he pushes it at a rivet line to ensure he doesn’t bend the sheet metal, but otherwise it’s ok. Paul describes how the system is built. He said in a Skyhawk the rudder pedal tension is created by springs that pull them toward the firewall. There’s not a cable tension spec. The steering bungees are between the rudder pedals and the nose gear. If you get in and push the pedals when stationary, you are putting stress on the bungees. Jarek wants to know if the FAA has lost its mind. He is wondering about the FAA’s AC 20-105, which says that engines that run past TBO have a higher rate of failure, and that engine overhauls at TBO are usually cheaper than those that are run beyond. Mike said Lycoming had previously issued a white paper that said that the typical lifespan of a crankshaft was 14,000 hours. Camshafts have corrosion issues, and don’t cause failures, and sometimes gears need to be replaced. But rarely does time impact safety. There are people inside the FAA who disagree with the policy, Mike says. On one hand they require manufacturers to set a TBO. On the other hand, they tell Part 91 operators that they can ignore it. Typically engines that fail that have run beyond TBO tend to be not related to age, but because of maintenance resulting from the fact that the engine is older. In fact, it’s usually the opposite, Mike says. Lower time engines typically fail because of infant mortality. Aaron and a partner recently purchased a Seneca with turbo Continental TSIO-360-KBs. They installed new intercoolers and the manual revision suggests new power settings. He’s ignored the chart and is flying around 30 inches lean of peak. Mike said the chart is interesting if you are operating rich of peak, but irrelevant lean of peak. The power output of the engine is determined by whichever component is in shortest supply. Rich of peak, you have more fuel than you need, so power is controlled by air through the throttle and the prop. Lean of peak, fuel is in shortest supply, so power is controlled through the mixture. He would run a slightly reduced throttle, just to avoid overworking the turbos. Rory has a Cardinal that he bought 12 years ago, and he hadn’t ever changed the ignition wires. So he started to wonder about when and why to change them. The hosts agree that if a wire fails it feels like a stumble or mis-fire because it just takes one spark plug offline. They say to run them on condition, and only change them when they start talking to you through mis-firing.

Metal in the filter, starting problems, and mechanics who don't understand the definition of installed are on tap this episode. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: Roger has a Mooney M20J that has developed an odd starting problem. Over the past few years he’s had to increase the time the boost pump runs before the engine will start, and even then it sometimes doesn’t fully catch. Paul suggested that the bellows inside the flow divider could be bad, which would cause it to perform poorly. Mike also suggested that the idle mixture could be set incorrectly as well. An rpm rise test can verify if it’s correct. Craig has a 182 that he uses to go back and forth to his fishing cabin. He took the back seat out and he wants to add in some plywood in the back to protect the structure. He isn’t planning to affix it in any way other than Velcro. His A&P told him to avoid doing this because the wood isn't burn certified. But without installing the plywood with a structural fastener, it’s not technically installed and he can carry it however he likes. Malcolm has an 182 with the Texas Skyways conversion, and it hangs up during the starting sequence. They’ve replaced the starter, bought a battery tender to check the battery, and more. It’s so obvious what the problem is, Mike says. This is a classic and common problem among Continentals. The starter drive adapter is bad, the hosts say. He can have the part repaired and it should no longer be a problem. Aaron found a significant amount of metal in the oil filter on his Piper Cherokee 140. There was aluminum in every pleat of his filter after only about 15 hours. They were thin, but large flakes. The pieces were too big to even show up in an analysis. No other metals were elevated in the analysis. Colleen suggests that it could be from the oil pump impeller, but since he only found oil in the filter, and not in the sump itself, he thinks it’s coming from the pistons. Mike said piston pins migrate back the other direction, which often means it’s self-resolving. As it turns out Aaron knew the answer. He removed all four cydlinders, and two of the piston pins were severely worn. They also found ring chatter. Mike said Superior has had issues with ring chatter and they’ve tracked down the manufacturing problem and replacing the cylinders under warranty. 

An airplane that hasn't flown in 8 years quits when going to full power. A turbocharged Mooney meters out less fuel as it climbs. Mike, Paul, and Colleen tackle these questions and many more in this episode. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below Eric is having trouble with his Aero Commander. The engine has only 150 hours but sat for 8 years. After an extensive annual, they test flew it. One of the engines dies at full power, but runs fine at partial power. The flow dividers were checked, the fuel lines were blown out, and the fuel servos were bench tested. Colleen suggests that it could be a blockage of the exhaust, especially given the long sitting time. Paul thinks it’s possible that a lack of air supply could be a problem. They suggest opening the alternate air to see if that fixes it. Paul said he would go through the entire induction system to verify it’s clear and open. Will is struggling to get the fuel system set up in his turbo Mooney. As he climbs he says the fuel pump is decreasing fuel pressure. The manifold pressure starts to decrease when fuel pressure gets low in the upper teens. Mike said there’s nothing wrong with the manifold pressure or upper deck pressure. The line from the upper deck pressure to the fuel pump aneroid is bad. The aneroid thinks it’s seeing lower pressure as he climbs, even though it shouldn’t. He thinks there’s a leak in that line, the aneroid, or the upper deck pressure. He suggests pulling the b-nuts and replacing the seals first. Jim is wondering about how to lean when flying low in a formation fly-over. With 10 airplanes and lots of throttle changes back and forth, it’s hard to know how to lean. Colleen suggests doing some tests at the same altitudes not in formation to see what sort of power settings he’s at and apply it based on those tests. Mike said he would lean to around best power. Jason is a partner in a 182 and a potential new partner went for a test flight and found a potential issue. The rpm dropped 150 to 170 during the mag check, and he refused to fly the airplane. So he’s wondering if the pilot was overreacting or if he was right not to fly it. Paul said EGT rise is a better indicator than rpm drop. Very little drop or no drop could mean the P leads weren’t connected. Mike said bigger drops, like 300 rpm, should prompt a timing check. Switching to one plug has the effect of artificially retarding the mag timing. If it’s already retarded, that can make a large drop

Live from Airventure 2024, we present the first of two sessions. Listen as the audience tries to stump Mike, Paul, and Colleen with its toughest maintenance questions. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join

An owner wants his engine perfect for flying around the world, how to start an airplane with electronic ignition, when to fire your mechanic, and defining approved data are on tap for this episode. Submit your questions to [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full show notes below: Ethan is flying a 182 around the world, and he is worried about a CHT imbalance. He’s added an electronic ignition, changed some baffling, changed cylinders, and even got a new engine. It also gets worse as he levels off. Paul said Ethan still has a baffling issue, and the first step is to cut slits in the material to make sure it’s laying flat. The temperature imbalance changing when leveling off makes sense to Paul because the airflow over the engine changes as the pitch of the airplane changes. Mike said it can be inter-cylinder baffling as well. Even CHTs are impossible, he says. A 50-degree spread is good. Colleen suggests pushing the baffling off the back cylinder by wedging in a spacer between the cylinder and the baffling to create a small gap. Frank just installed an electronic ignition for his 182 and is wondering how to properly start the airplane with a split switch. He has been starting it on battery only, as per the airplane handbook. Paul made the point that older Cessnas didn’t have a split switch. Theoretically with the alternator on during the start, you avoid an electrical jolt, although he said he can’t say the battery only start is always better. He recommends starting on both mags. Mike said the only time you wouldn’t want to turn the alternator on during a start is if you have an almost dead battery. It’s more important to avoid the jolt on a gear-driven alternator. Benny is headed for a bread-up with his mechanic. He likes the work the mechanic has done, but in talking to the mechanic about his approach to maintenance, he is concerned they don’t agree on tactics. The mechanic doesn’t believe in lapping valves, for example, and may have a hard adherence to TBO. Benny wants to know whether to switch now or try to work through the disagreements. Mike thinks it’s worth a conversation given how difficult it can be to switch mechanics. Colleen said it’s not going to work, and that the mechanic is most likely set in his ways. Paul agrees that getting a mechanic to change his mind is incredibly difficult.  Dwayne is restoring an antique airplane is wondering what constitutes approved data. Xerox copies are acceptable, despite what others have told him. He also wants to know if reverse engineering a part is considered approved data. Dwayne and the hosts discuss the difference between acceptable and approved data. 

An owner wants to know if he should tear down his engine after harvesting some corn with his prop. Plus, the benefits of flying oversquare, why you should use the boost pump at higher altitudes, and pre-flight procedures. Send your questions to [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: John wants to know if he can manipulate the rudder on his club’s 172 during a preflight. Another club member told him he would stress the nosewheel steering by doing that, but the hosts agree that John that was right. Paul explains that the tension on the rudder pedals is created by springs that pull the pedals to the firewall. The steering bungees are between the rudder pedals and the nosegear, not the rudder. The rudder may move the pedals a little. Bigger stress is when you move the pedals from the cockpit without the nosewheel moving, but even so, Paul said the system is made to do that and is unhurt by those checks. Jeff had a botched landing in his Super Cruiser and hit some corn at full power, and he is wondering whether or not he had a prop strike. The engine didn’t seem to have an rpm drop, and the prop was undamaged. Mike said there’s two possible outcomes. The first is that he didn’t have a prop strike because there wasn’t a reduction in rpm. If Jeff thinks he had an rpm reduction, the AD requires the accessory case to be removed, but not torn down. In all the prop strike events Paul has been involved with, he’s never seen rotational damage due to a prop strike. Magnetos are usually the first thing to be damaged. He said he thinks it’s also unlikely there wasn’t an rpm reduction as it slashed through the corn, and he thinks Jeff is subject to the AD. Tyler is looking at buying a turbo Piper Arrow and he has questions about turbocharging. He wonders about the diminishing returns of oversquare or overboost as it relates to reduced longevity. He’s also worried about boot strapping, which Paul said is self-limiting. Mike said the highest amount of oversquare allowable within the operating envelope is the most efficient place to operate. It’s important to remember that the chart is rich of peak, and lean of peak provides more of a detonation margin. Mike said the abuse to worry about is horsepower per cubic inch. Fred’s engine on his Cirrus had a hiccup and he’s wondering why. He was at 10,000 feet climbing in the clouds. One cylinder was getting hotter, and one had passed 400, so he leveled off, things cooled off, and he started climbing again. Just as he leveled off he tried to do the big mixture pull, it stumbled, so he pushed it forward and it still stumbled. The hosts quickly figure out he had vapor lock. Paul said a lot of Cirrus pilots run the boost pump on low all the time. Mike does that on his 310. With a hot engine and high altitude, the fuel is vaporized, so the boost pump helps move things along a bit. 

Lots of leaks this episode, as Mike, Paul, and Colleen diagnose a leaky strut, a defroster that's not working, a leaking brake system, and more. Send your questions to [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Greg has a Cherokee with a leaky strut. His mechanic suggested pressurizing it with shop air instead of nitrogen. He asks about Granville Strut Seal. Mike said he has a big success rate with Granville, and that he should definitely use it on all the struts. He disagrees with Greg’s mechanic that shop air is ok to use to fill a strut. The reason to use nitrogen is to avoid corrosion inside the strut because shop air has moisture in it. The air valve in the top of the strut is probably where his air is leaking from. Jim has a Mooney M20C and the defroster ducting is falling apart. He’s wondering how to replace it. They recommend taking out the glareshieild, grabbing out the tubing, and buying a new one from Lasar or the factory. The existing one might be repairable with epoxy or new fiberglass pieces. Paul cautions that it’s possible something won’t work after he gets it all back together. Mike thinks it’s almost not worth fixing because of the complications in that tight of a space. Andy is trying to understand the carb ice potential of the Cessna with an O-300 that he’s flying. He’s heard it’s very prone to icing, and the carb temperature gauge shows it’s almost always in the yellow. To stay out of the yellow he would need to fly with the carb heat on almost all the time. Mike said the extreme dryness in a Minnesota winter would make carb ice unlikely. Nick has a few questions about his 182. He’s first wondering when to replace the battery. Mike said that the way to check is an annual capacity check, and there’s an official and unofficial way to do it. The official way is to buy a capacity checking instrument, but that’s expensive. First fully charge the battery, then time how long it takes to go down to a certain level. If it gets below a certain ampere-hour rating, it’s time to replace it. Unofficially you can draw current in the airplane and see how long it takes to draw down. But the act of the capacity check seems hard on the battery, according to Mike. Paul said Concorde has told him it’s not an issue, and that checking them doesn’t damage anything. Nick's second question deals with the brakes. When he bought the airplane he saw in the logbooks that they were being rebuilt once a year. He changed out the master cylinder, the flexible line, the o-rings, and he blew out the line. It’s better, but he still has to occasionally fill the reservoir. Paul suggests checking the line near the calipers. If it’s a solid tube, he said it’s possible that fluid can work it’s way back up the system. He suggests leaving a rag wrapped around the top of the reservoir and fly to check if that’s where the fluid is coming from.

This month Mike, Paul, and Colleen cover the basics. An owner wants to know if he should pull the throttle or propeller first in a climb, another wonders what the ideal power setting is for the run-up. Plus, mis-fueling and tired turbos. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full show notes below: John has a 210 and wants the definitive answer on whether to pull back the power or prop first. Paul said he has a 5-minute restriction on full power. He suggests after 1,000 feet, reduce the rpm only to 2600 rpm. Then reduce the mixture in the climb to maintain the exhaust gas temperature that was roughly at takeoff. Then when he gets to cruise he can set the rpm where he wants. But leave the throttle wide open all the time. Paul sets the rpm where the engine runs smoothest. After the mixture and prop are set, then he can go lean of peak. Mike said lean of peak is usually most effective at lower rpm. Ingram bought a Diamond DA-40 with the Austro engine and he’s worried about mis-fueling. The POH isn’t helpful because it only says to drain and flush the tanks if mis-fueling is suspected. The hosts aren’t aware of a test kit that ensures he gets jet fuel, so they recommend smelling the fuel sample because avgas and jet fuel smell much different. Justin wants to know whether to believe his instructor and general guidance, or the manual. He said he was taught to do the run-up at 1,800 rpm, but the engine manual for his airplane said to run it up at 50 to 65 percent power. Mike said it’s better to run the engine up lean, and that 1,800 is perfectly fine. Without proper cooling, he worries about engine wear with regular high-power run-ups. Royal is wondering if the turbo in his TR182 is losing it’s oomph flying higher. Paul said the fact that it’s turbonormalized means it lasts longer. The waste gate on his system is open until he gets much higher than most. Mike said turbochargers generally don’t lose power. It’s more likely the throttle linkage has changed over the many years that he’s owned the airplane. Paul said cam lobe wear can also be an issue. 

This episode Mike, Paul, and Colleen tell a flight school owner not to throw away a perfectly good engine. Plus, the origins of the annual inspection, safety wire, and poor engine monitor guidance. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Mike has a Cessna 150 with a bunch of advanced avionics, including a Garmin GI275 as primary engine instrumentation. The oil temperature setting frustrates him because it’s flashing cautionary at 200 degrees and warning at 210 degrees. The POH says the max is 240 degrees. Paul said the engine monitor should match the original gauge, so if there wasn’t a cautionary range on the original there shouldn’t be one on the electronic instrument. David is challenging the maintenance norms. He’s wondering how the FAA originally came up with the idea and time frame of the annual inspection. Mike thinks it’s arbitrary because some things should go less than a year, and some can go much longer. Firewall forward and wheels and brakes should probably be less than a year, but things like cable tensions could go less. The phased inspections that turbines go through is more logical, he thinks. The airplane in Albert’s flight school is difficult to start, and his mechanics can’t figure out why. They’ve looked at spark plugs, adjusted the fuel, fuel servo, magnetos, and more. They recommended replacing the engine next. Don’t do that, the hosts say. Mike asks for the starting procedure. In Albert’s write up he mentioned having to wait some time prior to trying to start again. Mike said the only way that would happen is if the engine is continuously flooded during starts. Paul said if there’s leakage in the flow divider, the engine can become overprimed because its as if it is being continually primed. Colleen said it’s not a bad idea to check the ignition harness and other electrical components. And Paul said to also look at the P-leads. Slavic is learning to fly helicopters and he was surprised to find that none of the oil filters were safety wired, and he wants to know if it’s safe. The hosts are shocked. However, a safety bulletin from Robinson says that it’s not required. 

This episode a perspective owner wonders about the cost of tying down outside. Plus fuel pump problems, major versus minor, and more. Email [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Steve’s primer in his Saratoga sat for a long time and was pumping air when he came back to fly it. He had to track a fitting to get it to pump fuel again. Paul thought that since the pump is lower than the level of the fuel tank, then it should have probably been ok with the long break from flying. He suggested that air had gotten in the system somewhere other than the pump. Although the problem hasn’t re-occurred, he wants to be sure there aren’t underlying problems. The hosts think since there aren’t any stains from leaking fuel that he probably doesn’t have an issue. Dennis is looking to buy an airplane and he’s trying to establish the maintenance costs difference between having a hangar and being on a tie-down. They recommended a cabin cover to try and keep the water and UV out of the interior. Dennis is worried about the freeze-thaw cycle during his cold winters, but the hosts aren’t concerned. Paul said not to worry about all the snow that sits on airplanes during the winter either. Dennis asks about glass versus steam, and they suggest that maybe glass would fare better in cold weather. Mark wants to install an air conditioner as a minor alteration in an Aerostar. He and the hosts talk in detail about the challenging issue of minor versus major alterations and what’s involved in that decision. Mark’s concern is that the air conditioner should have a few operating recommendations about usage, recharge, and so on, and he is worried about pushing into the major category. Adding limitations and a flight manual supplement would do that, but the hosts think he could legally offer operating suggestions that don’t cross into limitations. Andrew works at a flight school with some airplanes have that airspeed in knots and some in miles per hour, and he is looking for a way to make life easier for his students. They discuss the issues involved with glass displays that are incorrectly labeled, and what that does to the legality of the airplane. Mike thinks so long as the original backup instrument is still legal that is probably ok. 

Is there a limit to how much oil consumption is too much? This episode, Mike, Paul, and Colleen answer this important question. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Jim has a Cardinal with 3,000 hours on the engine. Everything looks good, except that the oil consumption has increased substantially. They tried the ring flush procedure, and saw the fluid coming out of the carb intake and exhaust manifold. The second cylinder took an immense amount of effort to pull the prop through. They took that cylinder off, and found that the oil control ring had a lot of crud. Mike said he wouldn’t get too invasive in order to solve the problem. It’s not a safety of flight issue. They suggest replacing the cylinders only if the oil consumption bothers Jim and his partner. Jim’s partner suggested also overhauling the bottom end with cylinder changes. They advise against it, instead looking at the cam when the cylinders are off. Mike wonders if the ring flush was done wrong. None of the fluid should come out of the exhaust or carb. He and Paul said they’ve never seen fluid come out of the valves. They recommend trying again. Nicolas and his partner disagree on how often they should change the oil on their Grumman Tiger. His partner wants to change the oil before the winter, when they usually only fly a few hours, and then again in the spring, when they fly around 30 hours. Mike said the oil change intervals are inexact. As the airplane is flown, the oil gets increasingly corrosive. He suggests not letting the airplane sit with old oil throughout the winter. So that’s when he would change it. He’s wondering if he can avoid changing the oil in the spring after only flying for seven hours over the winter. The hosts agree that it’s probably fine not to change the oil at that point. They recommend also getting a dehydrator to keep the inside of the engine dry. John has a twin Cessna with one engine that quits when it’s cold. Mike said the fuel pressure at low rpm isn’t high enough. Or the idle mixture isn’t rich enough, or there’s something wrong with the flow divider. The easiest and cheapest thing to do is to adjust the fuel pressure or the idle mixture on the fuel control unit. Paul said his Cirrus does the same thing in winter. He thinks it’s the fuel divider. Cheryl has a Skycatcher with a window tint and she is concerned about its legality, and whether it should be noted in the airframe logbook. So long as it doesn’t inhibit the view, the hosts think it’s fine. 

Can you fly a turbocharged airplane lean of peak? Absolutely! This episode, Mike, Paul, and Colleen describe how to do it. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below. Mike flies a turbo 206 and a 421 and is trying to fly lean of peak but the airplanes are running a bit rough. He wonders if there are tricks on turbocharged engines. The GAMI spread is half a gallon, so that’s not an issue. Paul said to start by getting the magneto timing really close and gap the spark plugs very tight. Mike said he might be trying to keep the cylinders too cool, which would make it run rougher. He recommends targeting 400 or 410 degrees on the Lycoming engines. Adam read Mike’s column in AOPA PILOT about LSA viability when the manufacturer goes out of business. He’s been interested in buying an LSA, but the story gave him pause. The FAA wants nothing to do with LSAs, Mike said. The hosts then discuss the differences between certification and ASTM acceptance, and what it means to potential owners. Garhett has had a bunch of maintenance-related failures, and it has prompted him to be more involved in his airplane’s maintenance. He’s now wondering the best way to obtain his A&P certificate. Paul suggests he should start by reading the FAA manuals. It took Mike 10 years to amass the required hours by working on his own airplanes under supervision. Short of going to school or getting a job as an apprentice, this is the best route. They then discuss creative ways to build experience. Victoria wonders how to keep the family airplane clean when the airport doesn’t allow water to be used. Mike and Paul suggest flying somewhere else and washing it. Colleen said she would use water or cleaner wax from a spray bottle. Paul really likes Crazy Clean, but cautions against using anything other than water during pollen season. For windshields, Paul said Cessna recommends a lot of water, Dawn, and your hand. Definitely don’t use power tools, they say. 

A light oil mist on his windscreen has one caller concerned he needs to split the case. Plus, Mike, Paul, and Colleen tackle cold cabins, tire changes, and horsepower calculations. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Grant has a Mooney M20F and he’s seeing a light mist of oil on the windscreen after flying. His mechanic thought it was coming from a case bolt, which he re-torqued. That didn’t solve the problem, and the mechanic said the proper way to fix it would be to split the case, which Grant doesn’t want to do. Paul said that’s not the problem anyway. He said misting oil on the windscreen is almost always the crankshaft seal or the prop o-ring, both which should be fixed together. The parts are cheap, and the job is relatively easy. Colleen just did this on her airplane and describes the process. Joe’s kids are freezing in the back seat of the family Cherokee. They’ve put tape around some gaps, and while it’s helped a little, it’s still very drafty. Paul mentions the spar carry-through gap between the cabin and the wing. There’s supposed to be a piece of foam in the gap, but often when the wings are removed the foam isn’t replaced. The floor is lifted up, and you can look in the gap with a flashlight and mirror to see if the foam is there. The rear spar also has a gap where there should be rubber discs glued onto the box where the flight controls pass through. Todd is curious how JPI derives the horsepower number. Mike said JPI keeps the math as a closely held secret. But he said there’s a right way to do it, and it's how Savvy does it. Power is regulated by air or fuel, whichever is in shortest supply. Rich of peak, you have more fuel than the engine can combust, so air is in short supply. Mass airflow is therefore the power determinate, which can be calculated with manifold pressure and rpm. MP is how much air goes into the cylinder, and rpm is how often that happens. Multiplying the two gives the mass airflow number. Power when lean of peak is a function of fuel flow. Fuel flow times a set number based on the compression ratio gives horsepower. He thinks the engine monitor doesn’t know whether it is rich or lean of peak, so it probably computes it both ways, and the lower number is the right one. Seth has some dry rot on his tires and he’s wondering if that means he needs to change thems. Desser says they need to be replaced when the cord is showing, and his mechanic says the dry rot means it should be changed. The hosts agree with the manufacturer that there’s no minimum tread depth, and to keep going.

A Vans customer wonders what to do next, and a 172 pilot asks if carb heat is really necessary all the way to the ground. Plus, the best spark plugs, and a vexing gear issue are on tap for Mike, Paul, and Collen this time. Email [email protected] to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Greg has a kit from Vans on order and he’s wondering what to do next. He can replace his quick build wing kit with the small cracks installed, but he wants to know if he should order replacements. Paul said when sheet metal work is done on certified aircraft in the field, a lot of cracks naturally come up. Greg said a customer has to agree to accept the modified terms of the new contract, and you have to either accept what they send you, or spend money on a second kit. Paul said to deburr as little as possible. The goal is clean, sharp corners, not a knife edge that can cut the rivet. Just barely touch the hole, he said. Travis has an unusual gear problem. He was tasked with ferrying a Wheeler Express RG, an unusual experimental. On the ground the gear works perfectly, but when flying it won’t reliably retract. The system is based on a Glasair 3, and Colleen said the Glasair racers have a similar experience with their airplanes at Reno. On a ferry flight the hydraulic fluid built pressure over a few hours, and Travis had to select the gear down lever in order to release the pressure. Paul said not to spend any more time on the system, and replace it with something from Cessna. Brian wants to get to the bottom of the fine wire and massive plug choice. His shop said he had to replace all 12 fine wire plugs at the last annual, all with around 800 hours on them. The shop recommended Temptest massives, which is what he did. He’s wondering if there’s really a difference in performance. Paul said fine wires tend to idle a little better and smoother. Corrosion was an issue on older Champion fine wires, which is what Brian had. And the ceramic is thicker on Tempest. Fine wires also last longer, usually long enough to cover the additional cost. Mike said they cost about four times as much, but last four times as long. He said some people also report smoother operation at very lean mixtures and small fuel economy improvements. Colleen has fine wire Tempests in her Cardinal but massives in her Skybolt. Her fine wires run a bit cleaner and don’t need to be gapped. Brian has seen a larger EGT differential when flying lean of peak with the massives. Dennis has a 172 and he wants to know if it’s really necessary to keep carb heat on all the way to the ground. Mike said a newer Lycoming Skyhawk is less susceptible to carb ice, but his Continental O-300 is much more likely to produce ice. He recommends installing a carb heat gauge if he really wants to avoid having the carb heat on longer than necessary.

This episode Mike, Paul, and Colleen help an owner with an engine that randomly dies after 2100 rpm. Plus, the role of avgas as a lubricant, prop governor issues, and getting back into maintenance. Email your question to [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Dennis has a Cardinal RG with a prop governor issue. When it’s warm, the prop underspeeds just a little. He’s done a bunch of troubleshooting, and he is at a loss. The manufacturer said to send his prop in, but he is reluctant to do that given how often prop shops deem them unfit for continued service. Dennis is an A&P and he asks if he is allowed to open up the governor and work on it. Mike said he doesn’t advise it because he both can’t do it legally and doesn’t have the right tools. Both Paul and Colleen said their props do the same thing, and they recommend he crank up the rpm just a little since a small amount of overspeed is allowed under the type design. Luis is looking to get back into aviation maintenance after earning an A&P many years ago. The hosts debate the FAR, which says that a mechanic is current if the Administrator deems he or she so, or if the mechanic has served as a technician for the past six months. The hosts think Luis should use the preventative maintenance provisions to do the work without supervision. Jeff built an airplane with a PZL Franklin 235 and the engine won’t make full power. The static rpm is 2800, and anything beyond 2100 kills the engine. He thinks either his homemade exhaust is causing too much back pressure, or there was a manufacturing issue. He wonders if there’s a way to isolate the problem. The ignition timing is set to 32 degrees, which is the manufacturer spec. Mike and Paul recommend backing off the timing first to see what happens. Paul suggests he could also remove part of the exhaust to see what happens. Josh wonders if we are too eager to get off avgas, specifically because of its proprieties as a lubricant. He’s always heard that it lubricates valves, but Mike thinks it’s probably not a concern. It’s true that before valve seats were hardened, there was some microwelding, which led to valve seat recession. Lycoming switched to hardened valve seats in the 90s, and Continental switched in the early 2000s. There is a possibility that some of the older Continental cylinders could have problems with valve recession, but it's too early to tell. He details the work that AOPA is doing with the dual-fuel Baron, which is seeking to understand some of these issues.

Mike, Paul, and Colleen help an owner raise his oil temperatures, explain the rules around ELT battery replacements, debate the merits of a tuned exhaust, and help an owner whose airplane won't quit. Email [email protected] for your chance to get on the show. Join the world's largest aviation community at www.aopa.org/join Full notes below: Chris has a Super Decathlon with CHTs as low as 270 degrees and oil temperature around 150. Even with the oil cooler covered during winter, it still doesn’t get hot enough. Mike said they like to see oil temperature up to 200 degrees if possible. Chris can check the vernitherm by putting it in boiling water to see when it actuates. Mike said the oil temperature gauge is typically reading at the coolest part of the process, and the oil may climb 40 degrees higher. Curtis just wanted to change his ELT battery. His mechanic sent it away to a service center. He received an invoice with three options, none of which included replacing the battery. His standby current apparently tested high. Unfortunately Curtis was in an unusual situation with a foreign-produced part. There are two answers, Mike said. There’s the answer where you feel like you have to follow the manual, and one if you follow the regulations. The manual says the battery must be replaced by a Part 145 shop, but the regs allow the owner to do it under preventative maintenance. Mike contends that since the battery replacement section of the manual is not an airworthiness limitation, Curtis can just brush it off. Pierre-Louis and his club in Switzerland have a tuned exhaust system on their airplane and while he is seeing some benefits in terms of fuel burn and climb rate, he is most interested in the smoothness of the engine. He said it feels like having a 6-cylinder engine and he’s wondering if tuned exhaust systems offer better engine longevity. Colleen thinks it’s possible the engine is actually working harder (more horsepower), so she guesses that the engine longevity would be reduced. Mike said he disagrees because the engine isn't producing more power, its power is being used more efficiently. Paul suggests that less vibration is ultimately better for the engine. Frank has a Rockwell Commander 112 and when he shuts it down it sometimes diesels, or won’t entirely quit. Typically it only happens in the summer after a flight when it’s warm. Mike and Paul said the only way that happens is if the mixture doesn’t fully shut off the fuel supply. Mike said the mixture cable to the carb is the first place to check. Colleen suggests that it could be a leaking primer as well. Mike recommends fault isolating it by disconnecting the primer to see if it resolves. 

This episode Mike, Paul, and Colleen debunk myths, describe valves that are eligible for lapping, and cover the basics of the red box and leaning. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Maciej is a new private pilot who is questioning some operational procedures he was taught. He was taught not to put fuel back into the tanks after sumping it, and he thinks if you sample it and it’s clean, why not put it back? The hosts agree that if the sample is clean, put it back. He also wonders about oversquare on the impact on the propeller. A ground school he took says that it is too hard on the propeller to run it at low rpm and high power. Mike questions the validity of this, and Paul said to go ask the source because it doesn't seem right to him either. George has an airplane with some valve issues. Five of his cylinders have varying levels of green on them. He was told that four could probably be lapped, but the fifth has to be pulled. He’s wondering if green on a valve, which is later lapped clean, weakens or otherwise compromises the valve. Most of the green you see is green deposits, according to Mike. In early days of borescoping cylinders, the colors on the face of the valve were all we had to go on. Now, when we can position the camera between the valve and the seat, and can see if there’s erosion. If there isn’t erosion, it’s a good candidate for lapping. Mike said as long as the valve isn’t a train wreck that it’s worth lapping. Most people don’t do it aggressively enough. Doug is an instructor who was flying a Cessna 182 with a client and the owner didn’t want him to lean, even though they were flying higher than 8,000 feet. Finally he convinced the owner that it was ok to lean a little to smooth out the engine. Apparently the owner was worried about the red box. Since the goal is to stay below 400 degrees on the cylinder head temperatures, Mike thinks it’s hard to get 182 cylinders that hot at altitude, and below 400 degrees there is no red box. Paul makes the point that because power output at 8,000 feet is below 65 percent, you can’t hurt the engine by leaning.

With everything going electronic in the cockpit, will owner-produced parts become a thing of the past? Plus, Mike, Paul, and Colleen talk about their least favorite magnetos, deferring maintenance, and more. Email [email protected] for a chance to be on the show. Join the world's largest community of aviators at aopa.org/join Full notes below: Justin owns a Columbia 400 and he’s wondering if he can make owners-produced parts for some of his electronics. The hosts agree that this is a problem with aircraft maintenance. Because it’s difficult to show original design criteria for electronics, it’s hard to prove the part meets the original standards. There are a lot of things you can’t easily duplicate, Paul says. Ben is a new aircraft owner and a lot of the previous squawks were deferred. He wants to know what he can do to help keep the airplane in top form before the next annual. Most of what Ben mentions is preventative maintenance and relatively minor. Paul said to focus on corrosion issues, including at the forward and aft wing attachments. Those are steel attached to aluminum. If you catch it early you can avoid future maintenance issues. Paul recommends using FAR Part 43 Appendix D as a guide for the what Ben should watch for. Colleen said to focus on things that would be expensive later. There’s a lubrication chart in the service manual, and Paul said to use that and go over the entire airplane. David had a scary experience in his Lance. He was approaching an airport and lost power. He ran through a checklist and nothing helped. At about 400 or 500 feet, descending toward a beach, he got a stall warning. The stall warning caused him to pitch forward abruptly, and the engine restarted. He was able to come in and land normally. After some extensive testing they found that a spring had broken in a mag. David thinks that maybe the spring was wedged in the wall of the case, and dislodged when he pitched forward. The hosts don't see how that's possible, but without further information, can't make a better diagnosis. Ray has a P210 and used an in-flight mag check to diagnose a problem. He was flying back to the States from Canada and he noticed the engine was running a bit rough. He checked the mags and found one wasn’t operating properly. He later decided to stay on one magneto. He’s gone through three magnetos in the past few years. He wonders if continuing the flight on one mag was a good idea, and what he should do now. They all agree that he did exactly the right thing by continuing and flying on one mag. Mike said he hates pressurized magnetos, and he would swap them out for electronic mags ASAP. 

Why you shouldn't jam the throttle forward launches this episode. Also, Mike, Paul, and Colleen help an owner with high oil temperature, advise a builder on engine modifications, help ease the mind of an owner with water in his tanks, and discuss how best to use a borescope. Email [email protected] for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Juan has a turbocharged 210 and he's having trouble going full power on takeoff. He flies out of a high elevation in Colorado, and when he rapidly goes full throttle the engine will quit. It's a bad idea to jam the throttle forward quickly, Mike said. That's especially true with turbocharged engines. Mike said he throttles slowly enough that he's about at full power at rotation speed. Paul points out that even if your oil is at 130 degrees on the gauge, that's not the temperature in the entire system. Everywhere outside in the hoses, etc, is colder. Advancing the throttle quickly can choke the system. Also, in the turbo 210, you can't just slam things forward. You must modulate the manifold pressure because overboosting can flood the engine.  Andrew has a 310 with high cylinder head temps and oil temps on his right side. Some new plugs and new baffling has helped his CHTs come into control. His oil temp is still high. He's replaced the vernitherm, sent out the oil cooler for overhaul, and done some other troubleshooting. The hosts suspect airflow because it happens under reduced power on descent. There's a baffle that separates the cylinder and oil cooler that Mike thinks could be an issue. Paul suggests flying with a GoPro or a borescope camera in the cowling to see what happens in flight.  Dan is building an RV10 with an IO-540 that he's going to overhaul before he installs it in the airplane. He's considering going to 10:1 pistons and porting and polishing and he's wondering about performance and reliability. Mike throws a little cold water on Dan's plans. He thinks it's not worth the risk. Colleen made a pro/con list and she said they are forged, which makes them stronger. They are more energy efficient, but that means they burn more fuel. There's a different magneto timing. They run at a higher pressure, and that probably means they'll need to replaced sooner.  Dennis gets water in the left tank of his Piper M600. His mechanic checked the cap, didn't find an issue, and swapped caps. Now both tanks have water. Paul said it could be that there's no new water, but leftover water from long ago. The water that collects sticks to the sides of the tanks and then rolls around as little balls until it finally makes it to the drain port. In other words, he suspects it's all old water that is just working its way out.  John has a borescope and he's wondering how to best put it to use. Mike mentioned Savvy's new borescope image collection efforts, and he refers to the intro, where they discuss the standard set of images. 

Mike, Paul, and Colleen help an owner with a bad lifter that shows itself after oil changes, guide an owner through a change his maintenance schedule, discuss what constitutes damage history, and take a guess at why POH numbers change over model years. Send your questions to [email protected] for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Steve has a 1975 Taylorcraft with an O-200. After oil changes one of his cylinders has some valve clatter. It tends to go away sometime later, only to come back after the next change. The oil filters are always clean and the oil analysis is good. Paul said there’s not much he can do about it, and Colleen said it’s also not a big safety of flight issue. Mike suggests they measure the dry tappet clearance to see if it’s wide enough to accommodate a larger pushrod to help eliminate the problem. Colleen said she read about a technique to fly it full power for an hour to see if resolves. They call it an Italian tune-up. Jim is on board with condition-based maintenance, and wants to alter the rubber hose component change schedule in his Rotax. Mike suggests that Jim can extend the change interval to maybe 10 years because he lives in the Midwest, and keeps his airplane hangered. The hosts discuss their method for inspecting hoses, how to manufacture them, and the various materials and considerations. Ken is considering a Cessna 180 with damage history. It was repaired and has flown 200 hours since repair. The damage history in question wasn’t so much damage as an improperly installed part that was replaced. Metal was found in the filter, a top overhaul was completed, and the owner is confident the airplane is running well now. Mike said the two things he needs to consider are whether the cylinders were reworked appropriately, and whether they were installed correctly. Considering it was a reputable overhaul company, the hosts are confident everything is ok to move forward. Scott wonders why on the same airframe, the performance speeds change over time. Paul guesses that early performance numbers were a combination of optimism, marketing, and guessing. And newer numbers are spot-on and well tested. Mike guesses that aircraft generally get heavier over time and maximum gross weights increase, necessitating speed increases.

Prop hubs that were nearly scrapped, how to properly measure the oil level, semi-synthetic oils, and tachs that don't agree are on tap for this episode. Email [email protected] for a chance to get on the show. Join the world's largest aviation community today at www.aopa.org/join Full notes below: Bill has a Cessna 182 with a prop that hadn’t been overhauled for about 7 years and 600 hours. This past March he had to send the engine off for some work, and he decided to send the prop off at the same time. They told him the hub was close to being trashed because of corrosion. He’s worried if he had gone another year the prop would have been scrapped, and he’s wondering what he can do to maintain the hub. Paul said he regularly sends out props that are 12 years old and he’s never had a hub rejected, but Colleen said her hub was rejected for corrosion. Mike thinks prop shops are zero tolerance outfits. He said just because they find something wrong with it doesn’t mean it was unsafe. Prop failures just don’t seem to be a problem, the hosts agree. The bottom line: don't send out your prop unless you absolutely have to. Tate is wondering how to accurately measure his engine’s oil level. He suspects that we add oil more often than is necessary because many of us check the level after flying, and seeing it lower, think that we’ve burned oil during the flight. Paul recommends picking a consistent interval to determine oil consumption, ideally at least 24 hours after shutting down. He said if you check the oil level right after shutting down and it says 6, you probably have 7 or 7.5 quarts. Mike said the only way to check consumption accurately is to check how many quarts you add over the course of an oil change interval because that’s averaged over many more hours. Rex is trying to avoid sludge in his engine and knows synthetic oils cause problems, but he’s curious about semi-synthetic oils. Mike said it’s more of a concern in Continentals than Lycomings. He recommends if Rex wants to do that he stick to unleaded fuel. He is considering running 50 percent mineral oil to compensate for the problem of keeping the solids in suspension. The original tachometer and the tach in Pete’s JPI run at different speeds. After many years of operation there’s now a big difference in time between the JPI and the mechanical tach. He wants to know which time to use for maintenance and aircraft valuation. Always use whatever time runs the slowest, Mike says. 

This episode is all about engines--how to fix one that runs rough, how to save money when buying one, why one went bad so quickly, and how to preserve one during a build. Email [email protected] for a chance to get on the show. Full notes below: Brendan’s friend has a Taylorcraft with a tricky engine issue. It started with low rpms in flight, and has since been repeated on the ground. The mags have been rebuilt, both mags swapped, cylinders reworked, new carb swapped, new plugs, and they even bypassed the fuel system. Colleen suggests new plugs to ensure they haven’t been accidentally dropped or damaged. Paul suggests basic things such as the carb valve improperly moving. James and a few partners are looking at their first airplane. He’s interested in the costs and complexity of things such as retract versus fixed, constant speed versus fixed pitch, turbo versus normally aspirated, and more. Colleen said she recommends four-cylinder aircraft because of the cost and complexity. They all agree that constant-speed is a big improvement for not much more money. With retracts, insurance is a concern. Colleen said she paid a lot for maintenance the first two years on the gear, but it’s been otherwise trouble-free. Mike said turbocharging does add some expense. He said to budget to change the turbocharger once between engine overhauls, and maybe some additional exhaust system maintenance. Will found metal in his filter during an oil change and found a pitted lifter when borescoping, and is worried about a spalled cam. There’s only 200 hours on the engine and he flies regularly and uses Camgard. It did sit for six months during maintenance, but he had a dehydrator on it at the time. The hosts go through a complete troubleshooting and logic process to discover what might be wrong, and they plead with Will to get to his mechanic quickly before the case is split. Tim is building an RV-14 and just ordered his engine. He’s wondering how to keep it corrosion-free while he finishes the airplane. Their first advice is to follow the manufacturer’s guidance carefully to keep the warranty intact. It comes bagged with a desiccant pack that indicates if moisture levels get too high. But that system is only set up for a few months. Mike said you can only partially pickle it by swapping the desiccant packs, and maybe a dehumidifier. There are models that use desiccant packs, or an electronic one called a Black Max. 

How far can you go with preventative maintenance? The hosts discuss this, plus oil-soaked plugs, a strange fuel smell, morning sickness, and more. Email [email protected] for a chance to get on the show. Full notes below: Lamberto has a 152 with oil soaked plugs, and is having to clean them every 25 hours. He wants to fix the problem, not simply deal with it. His mechanic suggests a harsh chemical. He’s tried new plugs without success, the hosts agree his BY plugs are the best for oil-fouling anyway. A solvent won’t help, Mike says. He suggests a ring wash, which involves filling the cylinder with a mild solvent, then pulling the prop through the combustion cycle. That forces the fluid through and cleans little by little. If you try to pull the prop through it’s probably too late and the cylinder needs to be removed and the rings probably replaced. Colleen likens it to flossing. Darin is curious about how far he can push preventative maintenance. His thinking is that if you can clean and gap spark plugs then you should be able to do the same to fuel injectors, and so on. Mike says it’s not entirely clear. The FAA has issued a letter of interpretation basically saying that the list in Part 43 is a list of examples, not an exclusive list. Cristopher flies a 172XP in a club in Germany and wants to fly beyond TBO, and also solve an oil issue. He thinks it’s coming out of the induction system drain. The only way that can happen is via the intake valve. They recommend borescoping the cylinder to confirm the leak. Callum has a Bonanza and smells fuel in the cockpit when transitioning to lean of peak. Paul suggests checking the throttle body area behind the panel. The mechanical changes when you lean can cause it. Mike knows of another airplane where this has happened, and they isolated it to a leak in the fuel selector. When you lean a bunch of fuel goes back through the return lines, he said, and any leak could show at this point. Jason has a 182 with an O-470 with a cylinder that is acting up on start when it’s cold. His engine monitor shows very low EGT when starting, and takes as much as a minute to 90 seconds to come to temperature. The CHTs are also much lower. The hosts agree that he definitely has the symptoms of morning sickness, and it’s time to ream it. 

How cold is too cold the fly? Mike, Paul, and Colleen answer this question, and help an owner solve radio problems, advise an owner to fix his probes, and describe the process to become an A&P in the latest episode. Send your questions and comments to [email protected] for a chance to be on the show. Full notes below: Chad has a Cirrus and he’s looking for some cold-weather guidance. A mechanic told him that subzero temps aren’t recommended for a piston. The POH says that flights below -23 degrees Celsius need the cowl inlet plates. The hosts agree that there’s no problem flying in cold weather, but cold starting requires some care and preheating. Mike said the only problem with low oil temperature is that it doesn’t boil off the moisture, and low cylinder head temperatures could bring lead scavenging problems. Colleen said that lead deposits only matter on valves because it could prevent them from seating properly. But, that can be cleaned off if it occurs. Andy has an LX7, a turbocharged airplane. His TIT sensors don’t seem to be working. He’s been using CHT and EGT as a proxy for TIT and he wants to know if that’s a problem. Why not just fix it, Mike says. Andy said he is planning to fix it at the next annual, but Mike said to deal with it now. They recommend a range of troubleshooting options, but agree that it's not a probe issue. Darrell has a radio in his Ercoupe, but above 1,200 rpm it is static-y and unreadable. He’s checked the antenna, the coax, the mags, and more. Paul said it’s most likely a connection issue. He recommends starting with the Veclro microphone key switch. Next move to the microphone plug, which often oxidizes. The hosts also recommend checking the P-lead. Chase wants to get his A&P based on some of his own owner maintenance, refurb work, and building an airplane. He wants to know how to log his time. Mike said this is highly variable based on the inspector’s preferences, so he recommends calling the FSDO to ask what they want. When Mike went through this process he went back and recreated some of his previous experience on an Excel spreadsheet. Paul helps his employees get their A&P by recording the N-number, date, description, and time in a logbook. It’s important to note that there’s no calendar time limit of how far back you can go.

A compass that works on the ground but not in the air leads to a fun debate between Mike, Paul, and Colleen. Plus, the basics of lean of peak (again), jailbreaking a Rotax, and the liabilities of being a mechanic. Send your questions to [email protected] for a chance to be on the show. Full notes below: Blake flies a Mooney that has a compass with a mind of its own. On the ground it works well, but in the air it vibrates a bit, but otherwise doesn’t move. Paul said his fuselage can become magnetized, which would obviously impact the compass. To solve this he says you need to degauss the frame. Mike suggests he start pulling circuit breakers to see if that fixes it. Colleen thinks it’s a current issue since it gets better when the RPMs decrease. With higher RPMs the wires in the airplane essentially become small electromagnets. Lenny is concerned about the liability of working as a mechanic in retirement. Paul said there is liability, but that the job is worth it. Mike says you either worry about or you insure against it. He describes his idea of a maintenance club. The concept is that a group of aircraft owners comes together and hires a mechanic who only works on their airplanes. The mechanic makes more money and the owners have better access to service. Andres flies a Bonanza lean of peak, and he wants to make sure he’s avoiding the red box. Mike said there’s a theoretical red box that only exists at GAMI on a test stand. Everyone else must use cylinder head temperature. With CHTs of 380 degree F, Mike said Andres is completely fine. The red box has fuzzy boundaries. He thinks of it as shades of alarm as you get closer to the center of the box. Colleen said her technique is to get on the lean side and just operate where it sounds and feels the smoothest. James has a Rotax 912iS engine on an experimental. It requires about 40 psi in the fuel system to operate. He thinks by updating the fuel computing he could lower the fuel burn, which is currently 4 to 4.2 gallons per hour. Rotax offers a higher level of controller that the hosts recommend he buy. They also recommend he leave the fuel system alone and work on another upgrade instead.

While one owner has too much of a good thing and lots of shops to choose from, another is second-guessing if the massive check to the cylinder shop was necessary. In this, our first crack at twice-monthly episodes, Mike, Paul, and Colleen spend more time as therapists and counselors than technicians. Submit your questions to [email protected] for a chance to be on the show. Full notes below: Chris has a 182 with a recently overhauled engine that he’s concerned is making too much metal. In fact, the lab called after his most recent oil analysis to draw his attention to the report. The experts see the trends coming down a bit and think he really doesn’t have anything to worry about. With a clean filter inspection, they recommend keeping an eye on it and continuing to fly. Mike has a Malibu and he recently replaced all the cylinders and he’s wondering if he wasted his money. His oil analysis had high nickel, and he was experiencing oil pooling and low compression. He wants to know if he could have lapped his valves to save the cylinders. Unfortunately for Mike they agree that the valves would have been great candidates for lapping. Kevin has access to four maintenance shops on his airport. He has used two of them thus far and he’s wondering how to manage relationships and expectations when working with multiple shops. Mike said he’s a big believer in getting different sets of eyes on an airplane because each IA has his or her own style and focus. The disadvantage is that many shops will start from zero with a new customer, and doing the AD research and other items will take time and money. In Paul’s shop the IAs rotate airplanes, giving customers the benefit of multiple eyes under the management of one shop. He doesn’t recommend swapping shops every year, instead maybe waiting a few years. Steve has gone down the rabbit hole on the wobble test and he has come to the conclusion that the tool doesn’t really clear up the process. Paul said although he has a custom tool, he never uses it, preferring to just ream the guide and not taking the time to measure. 

Did Paul give us the definitive guide on how to hot start an airplane? Try his technique and see what you think. Also, unnecessary cylinder removals, a faulty tach, and a letter writer and guest who question if burping is safe. Send your questions to [email protected] for a chance to be on the show. Full notes below: Walt has a Seneca and has had to replace three cylinders in the last five years. He’s concerned that his mechanic caused the problem after hammering on his exhaust to remove it. The hosts don’t think the incidents are related. While it’s not usually a good idea to hammer on the exhaust, they think it could be useful and safe in limited circumstances. Mike hones in on the reason for the cylinder replacement, and encourages Walt to be more suspect of the need to replace the cylinders in the future. Tim thinks his tach is off. He has an alternative device that also reads rpm that shows a different value, so he’s wondering what he can do to adjust or fix his tach. Paul said the tach is technically adjustable, but being an instrument, it’s not something an owner or even most mechanics can do. Unfortunately the hosts agree it’s time to replace it. Luke operates a few Extra aerobatic airplanes, and he constantly struggles with hot starts. He has been resorting to blowing large fans up through the cowling, but that’s not always practical. In a Continental it’s recommended to run the fuel pump for about two minutes to purge the hot, boiled off fuel and flush the system with cold fuel. Paul said his technique works on Lycomings and Continentals. Start with everything forward with the pump on. Then listen, and as soon as the flow stabilizes and sounds like it’s pumping liquid, you’re done. Mixture and throttle back, but keep the pump on. Crack the throttle, engage the starter, and then advance the mixture control over a few seconds. Thomas has a Mooney and he tried the burping procedure from a recent episode. But the next flight his attitude indicator didn’t come online, and he heard that turning the prop backward can ruin the vacuum pump. The hosts have all heard this concern as well, but Mike’s never heard a confirmed case that turning the prop backward causing a failure. Regardless, this seems to be an issue with older styles of pumps. 

Live from EAA Airventure 2023, check out our second in-person show. The questions come fast, and everything from proper leaning to oil leaks is covered. Can Oshkosh-goers stump Mike, Paul, and Colleen? Full notes below: The first question has Colleen in stitches. Can you widen the gap on your spark plugs to get more horsepower from an engine? Short answer? No! Don’t do it, the hosts agree. Even Colleen, who races airplanes at Reno, says she’s never heard of doing this. Richard has a 182 and says the book will allow for high rpm and low manifold pressure, or low rpm and high manifold pressure for a given percent power setting. He wants to know which is better for the engine. The hosts say that rpm puts strain on the engine, so they would choose high manifold pressure and low rpm. The idea of “oversquare” is a relic and not at all true, they say. Julie has a 1979 Grumman Tiger and she wants the hosts to address owner-produced parts. Owner-produced parts must be made to the original spec from the manufacturer, which can be hard to track down. But, assuming the owner can find the spec, he or she must be involved in the manufacturing process. Ultimately it’s up to the mechanic to decide whether or not to install the part, and therefore take on all the liability. Bottom line is work with the mechanic early to get his or her blessing. Vedant asks how many more hours he can operate the 2,900-hour engine in his Bonanza. His engine has good compressions and only burns a quart every 20 hours. Colleen said conditioning monitoring is all about catching early indications of problems. Mike said there are only two compelling reasons to overhaul an engine. One is that you have solid evidence that there is something wrong in the bottom end that can’t be rectified without splitting the case. The other reason is that you can’t sleep at night. Terry has a 182 with an O-470 and can’t keep cylinder 1 below 400 degrees, even at altitude. That’s the right rear cylinder with a vertical baffle right behind it. He checked that. When it’s one cylinder Colleen said it’s usually airflow. Paul suggested a GAMI lean test and an induction leak test as well, just to be sure. Rex has a 182 and wonders about flying in the smoke that’s been prevalent around the country this year. The consensus is that smoke won’t hurt the engine, but changing the oil and induction air filter more often are good ideas. Tim wants to know about leaning his Mooney M20C. He wonders whether he should lean until it’s pretty smooth or really smooth. Mike said you have to accept a small amount of additional roughness if you want to run really lean. David has a 1979 172N and he’s wondering if he can use Camguard with his Lycoming 0-320-H2AD. Mike said he should use the AD-compliant additive just to remain legal. Greg asks for downsides to using variable-timed electronic ignitions in a carbureted engines. Paul said the risk is if they advance too far you can get into detonation. He recommends checking the cylinder head temperatures to make sure they aren’t too high. Advanced timing will show high CHTs and low EGTs, and retarded timing is the opposite. Jack has a Piper J-3 Cub with a Continental C-85 with only 40 hours. After flying he finds oil all over the belly but no obvious leaks. Paul said if the breather line is cut at the wrong angle it can actually cause a vacuum and draw oil out of the case. Mike said to borescope the cylinders with the intake valve open. It should be dry. If it’s wet you know where the oil is coming from. Mike asks about rpm on the ground and lead scavenging. The hosts say to lean as far as you can, regardless of rpm. Mike said not leaning on the ground is the biggest cause of valve sticking. Paul mentioned that Cessna now recommends leaning while at 1800 during the run-up and he said you can use that setting for ground leaning.

How to start an airplane, whether or not to wash an airplane for an annual, flying through smoke, and high T**s are all on tap for this grab bag of an episode, as Mike, Paul, and Colleen take your toughest questions. Write to [email protected] for a chance to be on the show. Tony owns a turbo Twin Comanche with 300 hours on the engines. He burns about 14 gallons per hour on takeoff, but he thinks he should be burning 16 gallons per hour. As a result, he gets high cylinder head temperatures quickly, and needs to reduce power. He also sees power surging on the ground when his engines are hot, but not cold. Paul thinks the fuel servos and engine-driven fuel pumps are both in question. Colleen recommends pulling one servo and sending it out, just to see if it makes a difference. Paul suggests maybe a different shop to see if he gets different results. He’s had many experiences where there’s a problem with a component that overhauling doesn’t fix, despite the overhaul facility saying there’s no issue. Andy questions whether shops follow the regulation that requires an aircraft to be cleaned during an annual inspection. Apparently his shop said they will wipe off big globs of dirt, but don’t do a full cleaning. Paul said they definitely wash the airplane, but often it’s after the inspection is complete so they can see the various oil and grease patterns. The wash is complete, but basic. Really dirty airplanes are written up as a discrepancy so the owner can take care of it later. Matt has a 210 and he’s worried about exceeding the turbine inlet temperature. They try to fly it below redline, but they exceed it easily and quickly on takeoff. They are hoping to more aggressively lean and take advantage of low CHTs. Mike said not to worry about going over the TIT redline for short periods. Redline on the turbocharger is meant to protect the turbine wheel because the blades can creep from centripetal force when they get too hot. But flying lean of peak is possible because TIT is often exceeded only briefly during the transition, and not when settled. He also suggested that unusual TIT numbers can be a result of improper mag timing. Nathan is a flight instructor and wants to clear up the madness around starting carbureted small engines. He sees people use the primer, pump the throttle, and do all sort of other unusual things. He wants to know the right way to do it. Mike said that using the throttle, or using the accelerator pump, puts the fuel in the wrong place. He also thinks that if it’s possible, prime while you crank the engine for best efficiency. Paul said if the primer isn’t helping to start the engine, it’s quite possible the primer isn’t working. He finds a lot of the old primers are clogged, which leads to other techniques. Erik has a question about how smoke impacts piston engines. With wildfires being more and more prevalent, whether or not to fly during wildfire season is a growing concern. Colleen said she sees increased dirt in her oil analysis, her air filter gets dirty, and the leading edges of her airplane get dirtier. But the hosts agree that it's generally not a concern, especially for brief periods.

In two separate but similar incidents, owners want to know whether their cracked spark plug insulators caused pre-ignition or if detonation ruined their plugs. Mike, Paul, and Colleen tackle those questions, and many more. Email [email protected] for a chance to get on the show. Full notes below: Mitch has a Mooney that developed a strong engine vibration a few minutes into a flight. He quickly discovered the problem as the cylinder head temperature was climbing, and he went full rich and reduced power. A subsequent borescope inspection discovered no anomalies, so he’s wondering what happened. Many people online said it was a clogged fuel injector, but Mitch suspects pre-ignition. So do Mike, Paul, and Colleen. They hone in on a cracked spark plug nose insulator. Mitch is also concerned about which came first. Did the broken insulator cause the problem, or did detonation break the plug? Thanks to good photos and data, the hosts are convinced there wasn’t a serious detonation event, and it was isolated to a plug problem. Brian wants Mike, Paul, and Colleen to comment on the validity of an unusual procedure. He has a friend that “burps” the engine after every flight, and he swears it keeps his oil much cleaner. It works like this: after every flight the friend will open the oil filler cap and turn the prop backward. Every time he does it a bunch of gasses escape. It’s a legit thing to try, say Paul and Mike. Colleen is shocked because it seems an odd thing to do, but getting a lot of the moisture out—which is the majority of what is coming out—can only be good for the engine. Les has a Lance, and on a recent humanitarian flight with a plane full of passengers his engine started shaking badly. With no good option to set down, he reduced power and nursed it back to the airport. No borescope necessary here, the evidence was obvious—total piston destruction. Again the hosts suspect a cracked insulator, and again they think it was probably the spark plug’s fault, and not something that originated with detonation. Mike doesn’t seem classic detonation symptoms on the cylinder. Les isn’t convinced since his mechanic didn’t find a cracked insulator, something Mike doesn’t buy. Even extremely small cracks can cause problems, and with such a violent event, it likely would have been cracked in the process. Richard has a new carb temp gauge and he is looking for advice on how to use it. Specifically he’s found that in some phases of flight he has to have carb heat on at least partially to keep the carb temp high enough to stay out of the icing danger zone. But he’s also heard that it’s bad to operate this way. The hosts agree that doing so could be bad, but with the gauge in place he shouldn’t worry. It gives him the information he needs to operate safely. Jay discovered a broken oil control ring after just a few hundred hours on a cylinder, and he’s wondering if his operating procedure caused it. Jay flies a Taylorcraft and it has a new carb that enables leaning, whereas previously it was always flown full rich. Not to worry, say the hosts. Excessive leaning wouldn’t have caused the problem, and he should feel safe to continue leaning. 

Paul and Colleen broadcast from Dayton, Ohio, for Aviation Maintenance Technician Day, and together with Mike, do their best to help owners suffering with engine problems, mysterious cold air leaks, improper fuel indications, and more. Send your questions to [email protected] for a chance to be on the show. Full notes below: Jim has a heavily modified Twin Comanche that blows cold air on the back of his neck, and he can’t find the source. He suspects it’s from the rear tailcone, but he can’t figure out how to stop it. Paul suggests it could be the rear bulkhead or from the wing roots. Despite his attempts, it’s actually gotten worse and is now blowing air on his legs that varies based on attitude, whether the heater is on, and maybe even heading. Mike suggests a camera and tufts of yarn in the tailcone to see where the airflow is coming from. Paul suggests that the airflow from the heater might be blocked, causing problems. They said if you pull out seats and floor panels on a test flight with a mechanic he might be able to find the culprit. Sam asks about dynamically balancing a propeller. When is it necessary? Who does it? The hosts agree it’s a good service to do when you change something, although the prop should be balanced from the shop. Arnold has a Bonanza that improperly shows the fuel level on the right tank, but only after it’s burned a few gallons. This is using Ceis fuel senders on a Garmin display. After many attempted fixes, it’s still reading low. Paul said they have to forget what they think has been eliminated and instead go and try to recreate the problem on the ground. Mike suggests putting a small vacuum on the tank to see if they can do just that. Keith has a turbonormalized Bonanza and wants to make sure he treats it well. He’s been surprised at how contentious the turbo versus non-turbo debate is. Mike said he thinks it’s a geographic problem where people on the East Coast think it’s useless and everyone out West thinks it’s a great tool. Although a turbocharged airplane is easier to abuse, the mechanisms themselves don’t have any inherent downfalls. So long as you treat it well and know that turbochargers are wear items, you should be fine. Ben has a Bonanza and he wants to know if he can remove the rear seats and remain legal by doing the weight and balance math based on station and equipment info from the manual. He also wants to exchange the fasteners to make it faster and easier. Colleen said a new weight and balance from an A&P is required once in order to be legal, and the hosts agree that fasteners approved for a later model Bonanza should be easy to get approved for his airplane. Kyle has a problem on both of his airplanes. His Cessna 182 with a bit more than 1,800 hours had a bent push rod and a bit of his lifter body had cracked as well. He is wondering if he should overhaul now since the case has to be opened anyway. Mike said the answer is always based on what happens after the case is split. If everything measures well then an IRAN is a good way to go, but an overhaul might be warranted too. It all depends on the inspection. The Continental C85 in Kyle's Luscombe has a stumble around 1,800 or 1,900 rpms. He thinks it might be a lean mixture issue because a bit of carb heat helps. Paul suggests he borrow a carb from a friend to see what happens. Even though Kyle has already overhauled his carb, Paul said he’s seen numerous times where even a supposedly overhauled carb won’t perform any better because they can’t duplicate the issue on the bench. A different carb would help to isolate the problem. 

A grab bag of unique questions come at Mike, Paul, and Colleen this month, including whether to buy new or overhaul, how prop stops work, what happens when you reduce from wide open throttle, and avoiding tiedowns. Submit your question to [email protected] for a chance to be on the show. Full notes below: Dale has a Seneca and he’s looking to the future and having to overhaul two engines. He’s wondering how to decide between factory new, reman, or overhaul. Not surprisingly, they suggest flying your current engines as long as possible if they are treating you well. When the time comes that you have to change engines, Mike said his general rule is that if the engine has treated you well to consider a field overhaul. If there’s a concern about the current engine, he said to consider a factory engine. More control over the process is another reason to do a field overhaul. Jim has a question about his L-3 with a Continental A65. He has an updated carburetor with a mixture control. A challenge with that engine is that you don’t get an onset of roughness when leaning. It just tries to quit, and without an electrical system, an in-flight shutdown isn’t ideal. He’s worried that a big stumble is startling and he pushes it too far rich again, putting him in the red box. Mike said there’s no need to go to roughness. You can lean only to the first indication of power reduction. Dubs has noticed that after leveling in cruise, when pulling the throttle back from wide open, it moves a significant amount before the manifold pressure changes. Yet in doing so he’s reducing his fuel flow. He’s wondering why this happens. Mike thinks it’s possible Dubs has a carb with an enrichment circuit, which gives more fuel at wide open throttle, meaning fuel flow will come down as soon as throttle is reduced. The hosts discuss how Dubs’ operating practice is how Cessna 182 pilots with 0-470 engines should operate to improve mixture distribution. The impact butterfly valves make is very non-linear, they say. The first 5 to 10 degrees of tilt won’t make a big difference, for example. Phillip is a maintenance tech in a shop that adjusted the low pitch stop of a prop based on the recommendations of the prop shop. He’s wondering why it was successful. Paul describes how a prop adjustment works, and why some airplanes don’t make full rpm until they’re down the runway a bit. Richard’s Rotax ran rough on a run-up, and after some troubleshooting he still hasn’t found the culprit. All winter it ran fine, but he’s concerned it will happen again in warm weather. Since this happened on both magnetos it’s likely not a spark plug. Colleen is wondering if the rpm range had an impact because the Bing carbs have three distinct operating ranges. If it happens again Colleen recommends isolating it and first checking the spark plugs, then maybe cleaning the carbs, and finally looking at the fuel delivery lines. Mike thinks it has to be a fuel system problem since it changes with temperature. Brennan has a nice Mooney M20J that he wants to continue to take good care of. He now lives in a very humid environment and can’t find a hangar. He left the airplane in his old hangar and can barely get to the airplane to fly it. He’s wondering what would be the least damaging practice—fly less or keep it outside. The hosts think it’s better to get the airplane closer and fly it while doing his best to keep corrosion away with freshwater washes, corrosion treatments, and maybe covers.

With two important airworthiness directives recently issued for Continental engines and Cessna Cardinals and 210s, Mike, Paul, and Colleen dig deep on the surrounding capacity and safety issues. Then they take calls on the limitations of engine monitors, and how normal can look anything but. Submit your questions to [email protected] for a chance to get on the show. Full notes below: Michael has a turbonormalized Bonanza and he’s concerned his system isn’t operating properly. When full throttle on takeoff it overboosts, so he goes to partial throttle, which lowers the fuel flow. The controller and waste gate were both checked with no change. Mike says it’s a very bad idea to limit the manifold pressure with throttle. Continental says overboosting by 3 inches is a non-event. What is a big event is limiting fuel flow. The fuel flow is determined by the upper deck pressure, which could be adjusted. Either way, Mike says that Michael can leave it alone and give it all the beans. Paul is shopping for an engine monitor and is wondering if the hosts have any advice. Of course they do! Mike recommends user-programmable alerts. Otherwise they recommend you buy the one that best fits in your panel. A slew of recommendations on how to use it follow. Laurie’s engine runs roughly in a certain rpm range unless she leans to peak EGT. The hosts soon learn that she operates from an airport at more than 7,000 feet. Mike thinks it’s likely this is normal behavior because the engine runs too rich at full power at such a high elevation. John thinks he might be experiencing morning sickness on his RV-7’s O-360 engine. He is noticing an increase of lead buildup each time he borescopes it. The CHTs are also too low, at around 300 degrees in the winter. He felt the engine was running rough for a few minutes after starting, as well. The hosts look at John’s photos and think his engine is perfect. Paul mentions that so long as the valve seats well, the gunk in the cylinder is fine. They offer a number of ideas on increasing his CHTs. Steve is frustrated with his engine monitor because he's experiencing what he believes are nuisance alarms. The issue is that his engine manual and POH have different numbers, and the engine monitor is programmed with the POH numbers. The engine monitor can be reprogrammed, but it’s expensive and requires input from a mechanic. This is mostly an issue with engine monitors that are certificated for primary replacement.

Mike, Paul, and Colleen debate the difference between a bribe and incentive pricing, discuss how much carbon in the oil filter is too much, counsel an owner how to keep his alternator belt on, and reveal what's in their go-bags. Email [email protected] for a chance to get on the show. Full notes below: Jim is finding a significant amount of carbon in his oil filter after oil changes on his Cessna 182. He wants to know if the carbon is a problem. Mike said the carbon itself isn’t a problem, but it’s indicative of something else that is worth tracking down. He said the oil is getting overheated, carbonizing it. It’s most likely from excessive blowby. They recommend compression checks and borescoping to see if he can find the culprit cylinder.     John flies a Mooney with an electronic ignition system, and he thinks the airplane is slower since the system was installed. Mike thinks it’s possible it wasn’t timed properly. They see it often because the electronic ignition system is timed differently than a traditional magneto. If the EGTs are up and CHTs are down, that's further confirmation.     Jim is frustrated with the alternator drive belt on his 182. It comes off the pulleys about once every 10 hours. Paul said it’s very common. Counterbalances on the crankshaft are a potential problem, but a last resort. Grooves in the pulley could also be the culprit, as could excessive play on the shaft on the drive pulley. Paul also suggests trying a solid belt instead of Jim's current segmented version.     David is trying to make a kit of tools and spare parts to take while on cross-countries, and he is looking for recommendations. Paul said he has two criteria. First is something you’re willing to change. The second is to take any special tools or parts that most shops don’t carry. Mike said he takes common-failure items for the specific airplane. On his 310 he carries a vacuum pump, for example. Colleen said she always carries duct tape and tie raps, a screwdriver in order to take the cowl off, and a first-aid kit.     Dustin has a controversial question about a recent interaction with a shop. During the buying process of an engine overhaul, an owner found out a supplier offered the shop $2,000 to the shop if the owner went with them. The owner found out thanks to the shop's honest disclosures, but questioned if this is an ethical practice. Mike thinks this is no different than a wholesale/retail markup. Paul said he understands why this feels different, but he thinks it’s legit. Mike recommends asking your shop what they are making on your part, and if you’re not happy with the amount to negotiate it.  

This month Mike, Paul, and Colleen give an owner the ammo he needs to not overhaul his engine prematurely, help console an owner with super hot cylinders--maybe, console another with super cold cylinders, and give cover to a pilot who wants to refill his own oxygen. Send your comments and questions to [email protected] for a chance to get on the show. Full show notes below: Pat’s Diamond has one suspect cylinder. The mechanic said it has failed inspection, and needs to be replaced, but the engine is beyond TBO and they are refusing to fix it without an overhaul. The question hits right at the heart of some of Mike’s frustrations with shops and their lack of evidence-based practices. He suggests lapping the exhaust valve to bring the compression back up, and then keep flying it. Kirk wants to refill his own oxygen system, but it’s not covered specifically in preventative maintenance regulations. The hosts asks if you’re allowed to add oil, fuel, and air to the various systems. Of course you can. It’s servicing the airplane. Mike says there is no talk of servicing in the regulations, but of course we all do it legally. They view adding oxygen in the realm of servicing. Robbie doesn’t believe his CHT gauge in his Socata TB-10. The factory single probe gauge shows 500 degrees and rarely goes below 400. He’s wondering what he can do to make himself feel more comfortable that it’s a gauge problem. Colleen asks if he smells anything. She smelled burning oil when hers went beyond 420. The hosts agree that given his great borescope photos, and good oil analysis that he’s probably ok. They also suggest checking the engine grounding strap that goes from the crankcase to the firewall. It grounds the engine to the airframe, and without it the probe wire could be finding some interference. The paint would also change color at 500 degrees. Will is seeing exceptionally cold cylinder head temperatures on his Comanche. On a recent flight to New York, he saw temperatures in the high 140s during descent. He knows his probes are good, so he’s wondering if there’s a lower limit and if it's hurting the engine. After discussing a number of possible causes, they discovered that Will is going full rich on descent, which is absolutely contributing to the low temps. Mike said that while you may have to enrichen a bit in the descent, if you forget the engine will remind you by running a bit rough. That’s followed by a detailed discussion of leaning for the climb and descent. Carl flies a Cherokee 180 and is wondering if flying it on cold winter days with density altitudes below sea level could hurt the engine. The hosts agree that the takeoff mixture setting is so rich that there’s enough of a margin not to worry. Detonation could be a concern in certain experimental engines, but a normal certificated engine has a big detonation margin. 

Did you know things live in jet fuel? These are the fun things you learn being a mechanic. Mike, Paul, and Colleen enlighten us on this strange fact, and tackle questions on leaning, burned exhausts, puddles of oil, and how not to set your airplane on fire when preheating. Email [email protected] with your question for a chance to be on the show. Full notes below: Chris owns a Piper Comanche with 1900 hours on the engine, and it that has developed an oil leak of one quart every 2.5 to 3.5 hours. Fuel tank sealant and an air/oil separator didn’t work. Paul says there’s no way he is leaking that much oil from a leak in the crank case. He suspects another issue. Mike said Lycoming has a procedure to slather a sealant on the case seam. Since there’s a lot on the belly Mike thinks it might be going out the breather. He suggests a ring wash. Lance flies a Cessna 185 and is worried about his leaning procedure. He’s recently replaced all six cylinders and is concerned his leaning procedure may have caused some problems. He’s worried that by learning until roughness and then enriching slightly he’s in the “red box.” Paul said if the engine is running rough, at least one cylinder has quit firing, so he's very lean at that point. Mike said the GAMI spread should be less than a gallon per hour. The GAMI spread is the difference in fuel flow between when the first cylinder peaks and when the last cylinder peaks. Assuming he only enrichens enough to stop the roughness, and no further, and his GAMI spread is good, he’s likely fine. If the CHTs are all below 400 degrees F and he’s less than 60 to 65 percent power, he has nothing to worry about. Chris number two asks about corrosion in fuel tanks. He works on turbine aircraft and often sees a brown staining on fasteners inside fuel tanks and he’s wondering whether it should be replaced. Paul said it’s only when the materials starts to degrade when you need to worry about it. He said a good rule of thumb is that if the part number imprint is still there that it can be left alone. Brad is wondering about pulling the prop through prior to starting. The general idea is apparently to move the oil around. Colleen said there’s no truth to any of it. You’ll scrape the oil off the cylinder walls if there’s any left. You can either preheat to heat the oil up on cold days, or you can pre-oil the engine if it’s been sitting a long time. Paul warns against pulling the prop through for safety. There’s no value in turning it backwards, and turning it forward can start the engine if you aren’t careful. Barry has a Tiger that had a muffler that lasted a long time when he ran rich of peak. Since running lean of peak or near peak his flame cones have burned out within 400 hours. Colleen talked to a local exhaust rebuilder who said he believes running lean of peak is burning up exhausts. It’s not because of the exhaust gas temperature, per se, but more likely the oxygen content of the flame at those mixtures. Jeff had a student with a Cessna 172 that he thinks has a tachometer from a Piper. It was replaced in 1993, and had been correctly signed off every year since. He’s wondering how that happens and what the pilot’s responsibility is in this case. Mike, Paul, and Colleen agree that an IA wouldn’t necessarily catch it on the inspection, although instruments and markings are part of the annual inspection checklist. Paul said he’s mostly concerned with the redline, and not necessarily the green arc.

Adam flies a Piper Warrior owned by his friend. On a recent flight he experienced some morning sickness that he was able to resolve. On a subsequent flight the owner had morning sickness as well. The owner is considering a top overhaul. Mike said he has two options, and a top overhaul isn’t one of them. The first is to do a wobble test and the second is to skip the test and go straight to reaming the valve guides. Paul recommends doing only one at a time. He said not to fly it again until the procedure is completed. They’re worried that flying it after the morning sickness could have caused damaged, so a borescope inspection is in order as well. AOPA r Kevin flies a Cessna 172XP that he suspects is the slowest one of its kind. It flies about 15 knots slower than book speed, and he’s seeking a remedy. Paul suggests first checking the rigging, specifically to make sure the flaps are completely retracting. If the flap rollers touch the end of the slots before the switch turns off, it will hurt the motor. But if there’s a gap after the motor has stopped, they aren’t full up. Totally ignore the fairing that’s riveted to the cabin, he said. He would also check the lifters to ensure complete motion. Mike suggests that is the airplane climbs at book values, he has a drag problem, but if it climbs worse than book, it’s a power problem. Greg is hoping to overcome the supply chain issues by purchasing a “lifetime” oil filter. Being able to open the filter is the best thing you can do to know how the engine is wearing, Paul thinks. Mike thinks the filter inspection, while possible with a reusable filter, would be a messy, complicated job. Ken said he heard an adage that you should check your EGTs at 1,000 feet, and then lean in the climb to match those numbers, and he’s wondering about its validity. The hosts all completely agree, and it’s generally how they fly as well. Patrick flies a Cessna 170 and he’s wondering why his cylinders have a different CHT limit. Mike thinks the difference is probably due to the fact that CHTs are measured in a different position in his engine than others and the O-300 has a different cylinder design. After a cylinder swap he’s also wondering why break-in procedures sometimes call for changing power settings. Mike said he’s never seen a justification for this practice. He has broken in his engines by running them as hard as he could, keeping in mind cylinder temperature limits. Miko maintains his own airplanes and is looking for approved data. He’s struggling to find reasonably priced maintenance manuals. Clearly the manufacturer is the first place to go. Paul uses ATP for his airworthiness directive research. Typically they sell subscriptions, which are quite expensive though. He said you might be able to get a shop to give you their old paper manual because most have transitioned to digital. Colleen also uses McCurtain, which they don’t think exists any longer. Essco is still around and sells digital versions of scanned manuals.

Engines are the focus this month as Mike, Paul, and Colleen talk about valve failures, valve springs, burned valves, and more. And of course we had to have a leaning question. Send your questions to [email protected] for a chance to be on the show. Full notes below: Marius owns a Cessna 172XP that routinely has a rough mag check on run-up. His mechanic is recommending fine-wire spark plugs after finding oil on the plugs. He has since bought them, which set him back more than $1,500. Colleen recently purchased some as well, and thinks they definitely work better. Nigel wants to get deeper into condition monitoring on his turbonormalized Bonanza, specifically with the turbo system. Mike said that the turbo controllers almost never fail. Waste gates are fairly problematic. Eventually they’ll start to stick, which you can tell by an inability to properly hold manifold pressure. The turbocharger itself is inspected at each annual. The shaft is checked as part of the inspection, and there should be a little wiggle in the radial direction, but none in the axial direction. Also look for blade scrape and cracks in the flange. Paul also recommends checking turbo system oil inlet and outlet check valves. Michael had a rough-running engine when he reduced power. They pulled the exhaust valve and found the keeper groove of the valve was much smaller than it should have been, and he’s trying to figure out what caused the problem. He’s now finding that the third cylinder is also behaving the same way. Mike thinks it almost looks like it’s been ground down. He suspects an installation problem. The hosts recommend pulling the valve covers and springs to check the rest of the cylinders. Viatcheslav is wondering about rotator spring failures and how they cause exhaust valve hot spots. He owns two airplanes, one with a Continental O-300 and one with a Continental E-225, neither of which have rotator springs. He's curious how and if his valves rotate without it. The hosts break the news that he does, in fact, own two of the few engines without them. He can continue to watch for hot spots on borescope inspections, and also occasionally lap the valves as a preventative measure. Reid is concerned about a burned valve on his 172. He leans aggressively, but doesn’t have an engine monitor, and wondered if his leaning led to the burned valve. His only source of information is the stock EGT gauge. Mike did some research on the Alcor gauge. Most of the Alcor gauges aren’t calibrated, and many don’t have temperature references. Some have an adjustable pointer that the pilot can set. Others have a calibration screw. On those, the manual tells you to lean to peak EGT at an altitude where you can get 65 percent power at wide open throttle, and then set the needle to match. Mike thinks the changes Reid is seeing could just be changes in the mechanism of the gauge. It’s not meant to measure absolute EGT. Furthermore, leaning doesn't burn valves. That's most often caused by a bad set.

Making new parts, protecting parts, replacing parts, and identifying bad parts is the theme of this month's episode. Plus, a spirited discussion on fuel selectors. Send your questions to [email protected] for a chance to be on the show. Full details below: Greg is building an RV-10, and he’s wondering if he should prime all the skins while he builds to ensure there’s good protection inside and out. Mike, Paul, and Colleen disagree on what to do. Paul thinks he should skip the priming and instead spray Boeshield or AV-8 because you can spray it on after the airplane is built. It’s a one-time application. Mike thinks if Cessnas have lasted for decades without being primed, Greg should be ok as well. And Colleen is on the fence. Bottom line: there’s no right answer, just the right answer for each builder. Russ is trying to help a friend. His 182R lower door hinge is cracked and the mechanic isn’t any help. Russ owns a machine shop and thinks he can manufacture the part. Mike says that it is important not to create a part that is better than the original. He must create an equal part. Something better would require additional approvals. Paul says it’s important to get the mechanic involved early because he will assume the greatest liability, and must be comfortable installing the owner-produced part. And many mechanics aren’t comfortable installing something without a part number. All agree that the hardest part of making the part will be figuring out exactly what the original material is and how it was made. Frank wants to use a synthetic oil in his 182 because he’s had such good results in his car. Mike makes the point that there’s no full synthetic oil on the market. He suggests 15w50, a semi-synthetic, but only because Frank is able to regularly run mogas. Those who only run with 100LL shouldn’t use a semi-synthetic, Mike said. Ryan is part of a flying club and they have a Cherokee 140 with an intermittent landing light. He was able to get the light to work regularly by applying a bit of heat to the circuit breaker, which makes him think the breaker is bad. The hosts recommended buying his own breaker and asking the mechanic to replace it. It’s a relatively easy fix. They recommend going to a pull breaker instead. Ernest said his mechanic hears a knock, but the hosts all agree that the video clearly sounds like lifter clatter. Mike say to look left, look right, make sure no one is around and pour in some Marvel Mystery Oil, which can reduce lifter clatter. When the lifter doesn’t fully lift there is play in the valve train, which makes the noise. Cleaning the lifter is an option, but it is a lot of work. Paul thinks it’s possible it only happens at lower oil pressures. With normal oil temperatures he should have 80 psi oil pressure at cruise, and not something lower, like 65. Alex sparked a spirited discussion on pilot technique. He’s wondering about how to test fuel flow on the ground. Some airplanes call for changing tanks on the ground, others don’t. Colleen thinks it’s ill-advised to switch tanks during the run-up. Paul said the fuel bowl on many carbureted engines contain about 30 seconds of fuel at cruise power. He said you’ll never run the engine long enough on the second tank to properly test it. This led to a long discussion about Cessna’s fuel selector design. Mike said he never moved the fuel selector off of Both in his 182, and furthermore he doesn’t understand why Cessna even made it. While the Cardinal will drain from the selected tank, the 182 doesn’t work the same way. If you burn off the right tank, for example, the fuel will be replaced with fuel from the left tank, and not air. Paul said he would stay on Both if he could. They then debate whether to use the fuel pump when switching tanks, and for many reasons Paul recommends sticking to the POH.

Because it's impossible to make it through an episode without discussing leaning, Mike, Paul, and Colleen hit it from two sides this month. A debate about inoperative equipment, and why mechanics reach for the pressurization cart first. Submit your questions to [email protected] for a chance to get on the show. Full notes below: Jay flies a Lycoming IO-540 on an experimental with one cylinder that peaks long before the others. He’s tried everything, including switching injectors. Mike suggests checking the valve lift to make sure the action is as good as the other cylinders. Paul suggests an in-flight manifold leak test to show things that can’t be duplicated on the ground. It works like this: Climb to 5,000 or 6,000 feet where the full power setting is the same as ambient pressure, stay at full rich on the mixture and let the EGTs stabilize. Then lower the manifold pressure by 7 or 8 inches and watch what happens to the EGTs. If one goes up while the others go down, or vice versa, it shows a leak in the induction system. Gary is a CFI who wonders about strain on a constant-speed propeller during power-off landing practice. With the engine at idle the hosts think it’s fine to pull the propeller back during gliding. Since his first question was so quick, Mike, Paul, and Colleen decided to give him another, and here Gary wonders if leaning to peak EGT is acceptable to the engine. We know leaning to 50 degrees rich is detrimental to engines, and we know lean of peak is safe if done properly, but little is said about running at peak. Given his comfortable CHTs, Mike said running at peak EGT is totally fine. And Paul said he ran at peak EGT for years in his Piper Twin Comanche with no issues. Eric wonders what triggers an overhaul and asks what happens once you go past TBO. Close condition monitoring is essential, says Mike. The two biggest tools are an oil filter inspection for the bottom end, and borescope for the top end. Oil analysis is also helpful, but Mike said the filter inspection is more important. Paul suggests making sure owners speak to their mechanic first to ensure they’ll sign off the airplane if the engine is past TBO. Although there doesn’t appear to be any legal basis to do so, some mechanics refuse to sign off an annual if the engine is past TBO. Scott wondered about inoperative equipment and how to decide if it’s ok to fly. Mike points to FAR 91.213D. Because it’s in Part 91 it applies to everyone, regardless of aircraft. It includes a logic flow that details how to deal with inoperative equipment. In order to fly with inop equipment it must not have been required for aircraft certification, in Part 91.205, on the aircraft’s mandatory equipment list, or be a hazard to fly without it. Toby has a Cessna 414 and has struggled with pressurization over the years, and he asks if his troubleshooting flow works well. He’s a little frustrated because most mechanics first hook up the pressurization cart, even though in his experience the test usually doesn’t show much. Mike said the cart is used to test the outflow side of the pressurization system because it bypasses the inflow system. Twin Cessnas have a very convoluted inflow side, where tons of things can go wrong. One reason to go straight to the cart is because troubleshooting the inflow side requires digging, Paul said. Troubleshooting mindset also matters. A slow-evolving problem is different than a sudden issue, for example.

This month Mike, Paul, and Colleen take questions from owners with round engines, fabric, fire-breathing aerobats, and more. Send your questions to [email protected] for a chance to get on the show. Full notes below.... Bruce has an a Continental O-300 and recently replaced all six cylinders. Number four is still running hot, and number six used to run hot. He played with the baffling to reduce the temps on number six, but number four is still around 400 degrees in cruise. He also added a splitter on the top to direct more air. He has checked the induction. By changing the baffling to help cool number six, Mike thinks he has made the problem worse for number four. The plate at the front is there to prevent number six from hogging all the cooling air, he says. When this happens Mike naturally looks at the inter-cylinder baffles, which are easy to mis-position. The first troubleshooting step is to shine a light from below and check if you can see it from above. If so, air can escape and cooling efficiency drops. Derek is looking to buy a Maule that’s been sitting in a hangar and he’s wondering how to check the condition of the Ceconite fabric. The Ceconite manual has inspection procedures. Colleen said it’s not the fabric you’re necessarily testing, but the dope. If the dope can block UV light then the fabric is presumably fine. If you push against the fabric and it’s pliable and flexible, that’s good. You can find the manual online https://www.conaircraft.com/_files/ugd/d66f5e_9653c858211f4636b7d4fcbb4787e540.pdf Oscar is wondering if safety wire isn’t meant to hold a torque, why don’t we use the same size for everything? Mike said there are three common sizes of safety wire, but almost everything is .032. Paul mentions that turnbuckles are an important exception. AC43.1B Change 1 https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_43.13-1B_w-chg1.pdf describes how to safety wire turnbuckles. An interesting and detailed discussion of turnbuckles that has nothing to do with safety wire follows… Scott has an N3 with a Wright engine and he’s wondering about leaning. The manual for the engine says not to lean, and he asks whether it would be better to leave it full rich or lean a bit. Mike calls for a vote and says that while in cruise he would lean it to the onset of roughness, and enrichen it only enough to smooth out the engine again. Colleen said she loves leaning and would lean as well. Surprisingly, it’s unanimous and Paul said he would lean as well. Bob has an Extra with a Lycoming IO-580 engine. He has noticed that his old Extra, with the same engine and virtually the same airframe, ran much cooler. He said he can barely lean at all now because of temperature limitations. Number five is the hottest, but only by a little. Paul wonders about his leaning technique, which is to lean slowly to find peak. The guidance is to pull much more quickly. The hosts also focus on a cabin heat shroud that’s in the cowling but not hooked up to the cabin. Bob thinks it partially blocks the exit airflow, which is a critical part of the cowling cooling system. 

Introducing our first live show from EAA Airventure 2022! Join along as Mike, Paul, and Colleen handle questions on the spot from the audience at the AOPA Program Pavilion.

Is shock cooling myth or reality? Can you run lean of peak with a carbureted engine? These questions and many more come at Mike, Paul, and Colleen in this month's episode. Send your questions to [email protected] Full notes below: Jerry has an RV-4 with a new battery but the original alternator. When he starts the engine and then turns on the alternator, he sees a big amperage spike. He tested turning on his alternator before starting, and sees the same spike. That piece of information is critical because according to the hosts it means it must be an instrument indication. Without the engine operating and the alternator not turning, it can’t possibly be producing current. Ken has a Mooney M20 and thinks the inside of the tail section is messy and ugly. He’s looking for a way to clean it out. A vacuum won’t work because the flakes are sticky. Paul suggests that because it’s sticky someone has sprayed a corrosion inhibitor and only hand scrubbing will get it completely clean. Once it’s clean, he suggests spraying in a thin coating of Cor-Ban (https://zipchem.com) or Ardrox AV8. Dave flies a 1946 Cessna 140 and a Hatz biplane with a carbureted engine. He wants to know how to fly lean of peak. Mike says that Lycoming engines are pretty symmetrical out of the factory, which means they are often ok to run lean of peak from the factory. Continentals are less so. The rear cylinders tend to run leaner and front cylinders tend to run richer. By reducing the droplet size you can better dial it in. Do this by using a little bit of carb heat to better atomize the fuel. The other method is to back the throttle off a little bit to make the airflow through the carb more turbulent. Without instruments to help, the technique is to lean aggressively until the engine stumbles and then enrichen only until the engine runs smoothly again. Steve is wondering about unleaded fuels in development. He wants to know if the hosts would hesitate to use any of these new fuels in their airplanes. And also if their operating procedures will change as a result. Mike, Paul, and Colleen say they would have no hesitation running one of the fuels once it’s approved. They also don’t expect any operating changes. Guest Mike wonders why the hosts don’t ever talk about leaning in a descent. Host Mike stresses that although power changes should happen somewhat slowly, it's not as slow as he used to think. Lycoming recommends limiting cooling to no more than 60 degrees per minute, and Mike has an alarm set on his engine monitor for 30 degrees per minute. The only time it ever goes off if he’s doing an “extreme slam dunk.” Colleen makes the point that aerobatic pilots often oscillate between full idle power. Hannah flies a Super Decathlon and wants to make sure she takes care of it while doing aerobatics. Colleen says to keep it under 6Gs and a close eye on the engine mounts because they are the flexible attach point between the engine and the airframe. Although Hannah was originally asking about general tips, the hosts find out that she has experienced a governor failure that spewed out almost all her oil. Mike asks about rpm overspeed and Hannah said she noticed that used to happen before the governor failed. She’s also seen a drop in oil pressure in the dive. If her inverted system isn’t working well it would starve the governor of oil.

Oil all over the nose, cylinders that are too clean, and bush propeller repairs. Mike, Paul, and Colleen handle it all this month. Submit your questions to [email protected] for a chance to be on the show. Adam wonders what to do after a prop overhaul left him with a huge puddle of oil and some shaken nerves. His plan is to remove the newly overhauled prop and send it to the manufacturer. Paul questions whether it was an install error because a seal between the shaft and the prop seal can be broken during the install process. Mike agrees and thinks the manufacturer won’t find anything wrong. Mike has a Cessna 150 with a 150 horsepower upgrade. He said the seller recommended not running it on Autogas because Lycoming never approved it. Mike says check Lycoming service bulletin 1070AB. It lists which fuels are approved for which engines. Paul correctly makes the point that the whole point of the STC is that it enables you to do things that the manufacturer wouldn’t necessarily have allowed. Mike said so long as there isn’t an operating limitation for specific fuels, you don’t even need the STC. Buying the STC gives you a flight manual supplement and placards. Lyle has concerns about his oil analysis and how it relates to the way he operates his Cessna 182. After an engine reman his chrome levels were going up, but are now coming down. His mechanic was concerned he was flying too lean because everything on the borescope looked too good. The hosts describe the ideal leaning procedure as this: Don’t look at any gauges. Lean it until it starts running a little rough, and enrichen it only until it smooths out, and no more. He also has high silicon levels, which Mike attributes to a carb heat door that isn’t sealing fully. Lyle further wonders about his exhaust gas temperatures, which Paul and Colleen remind him are irrelevant. EGTs are only useful for looking at trends, according to Colleen. Mike said it’s not a measure of stress on the engine—only a measure of how much energy is being thrown out the exhaust. Dewayne has an exhaust leak in his Tripacer. The two pieces of exhaust come together with a clamp, and a test shows it to be blowing more than bubbling. Paul said you can generally ignore leaks that only bubble, by blowing leaks need to be fixed. He recommends an expander and working very slowly to try and get the two pieces to better match. You can only push it about a thousandth of a inch, Paul said. Rowan asks how to know when a knick or dent in a propeller becomes unsafe to fly. We all check our props before we depart, but few of us have a guide to know whether prop damage is normal or unsafe. Paul said a good rule of thumb is that if you run your fingernail along it and it catches you need to address it. But if it just runs along roughly, but doesn’t catch, it’s ok to continue. But, that’s not an owner-approved repair. Mike said the problem is that they create a stress point. A sharp point at its apex is more worrisome than a rounded dent. Advisory Circular 43-13 Chapter 8 Section 4 gives details for mechanics on how to deal with knicks, and it’s actually a pretty generous standard.   Chris can’t fly as much he’d like, and he wants to know if he should risk a ground run if the airplane has been sitting but he doesn’t have time to fly. Water being a byproduct of combustion, a short flight can be more detrimental to a flight than letting it sit. If the moisture doesn’t boil off it only adds more moisture to the engine. Mike said where Chris lives on the Gulf Coast, he would buy a dehydrator. There’s no hard and fast rule on how long is too long to go between flights, but the hosts say once every few weeks is fine, and try to keep it to less than a month. 

From the seemingly benign--what tire ply to use--to the extreme--hitting 500 degrees on a cylinder--Mike, Paul, and Colleen face it all this month. And we mean all, like Ron's 172 that produces a loud bang exactly two minutes after shutting down. Submit your questions to [email protected] Full notes below: Larry has a turbonormalized Beechcraft Bonanza. When it came time to replace his tires he decided to go to with 8 ply, but he later researched and found the type certificate specified 6 ply. The Goodyear spec sheet seemed to indicate he would be over the weight limit on 6 ply. Paul said the older lighter Cessna 210s were 6 ply, but were upped to 8 ply later on. He suggests it’s ok to go up in ply if the dimensions are the same. Colleen also admitted she went from 4 to 6 ply on her Cardinal at the last tire change. Mike says if Larry is in violation by using a higher play, then he is as well. He mentioned a recent tire supply problem that prompted him to go up in ply. Randy bought an engine without logbooks that was intended for a Cirrus SR20 in Guatemala City. He’s wondering if he can put it in a Cessna 175 or Skymaster. Colleen brings up the lack of AD compliance data. Some ADs are for internal engine parts that can only be verified with paperwork or by opening up the engine. Ultimately Paul said it’s up to the mechanic who has to hang the engine and whether he or she is comfortable with its AD compliance status. Mike said from a safety standpoint he would want to pull the lifters and look at the camshaft. And he would pre-lubricate everything, including the cam while the lifters are out. If it’s not making metal within 100 hours, you’ve dodged a bullet. Tom is wondering how to tell if his engine with a constant speed propeller is producing full power. At sea level he has 29 inches of manifold pressure with an ambient pressure of around 30 inches. All the hosts agree that this sounds about right, given that you’ll lose some pressure through the intake and other areas. Jeff has a Cessna Cardinal with a recently installed electronic engine monitor. He saw on climb-out near El Paso that the cylinder head temperature on the third cylinder topped out around 500 degrees. Now he’s wondering what to do. Compressions are excellent and the oil analysis is good. He also fixed the baffles, which fixed the problem. Mike suggests borescoping the piston. Failure points would be corner melting or the pockmarked appearance of detonation. If the piston looks ok, you’re probably fine, he says. Ron has a 172 that has an unusual problem. Every time the fuel level is below half, and two minutes after engine shut-down, there’s a loud bang. It sounds like someone hit the top of the wing with a bat, he said. Paul thinks it’s possible the tank is being overpressurized, and the reason it takes two minutes is because the weep hole is so small that it takes that long for the tank to equalize. He suggests quickly depressurizing after landing by taking off a fuel cap and seeing if air rushes by. If the tank vent tube is in the wrong position it can cause the overpressurization. Robert has a Cherokee 140 that is burning about a quart of oil per hour. Mike said oil consumption is always a cylinder problem, but not always a problem with all cylinders. Borescoping the cylinders may help identify oil pooled in one particular cylinder. Oil consumption comes from three sources--crankcase compression, which will show as oil out the breather tube. Burning oil will show as soot on the airplane. Or there could be a leak. Paul suggests a ring wash to further identify the problem cylinder, and potentially solve the issue. A detailed explanation is available at bit.ly/solventflush

This month Mike, Paul, and Colleen tackle questions about inexpensively improving aircraft paint, cylinders that are too cool, low compression readings, and a magic floatplane that burns less fuel with its floats fitted. Plus, the ultimate stumper, an airplane that can't turn left. Submit your questions to [email protected] Full notes below: Eric has a Pitts with an unusual problem. When he turns left the engine starts to sputter, and when he turns right the rpm increases. They initially suspected the flop tube in the header tank. Although it looked to be in good shape they replaced it anyway. They also overhauled the wobble pump, and carefully inspected all the fuel lines. There were no obvious problems. Colleen reached out to Pitts experts. They suggested making sure the fuel divider was properly bled. Eric is pretty sure it’s not vapor lock. “It has to be the flop tube,” Mike and Colleen say. Another theory Eric and his mechanics came up with is the fuel controller. They sent it for service, and the shop found that the throttle body mounting hole had a little rounding from vibration damage. They thought that maybe turning opened it to allow in more air, leaning the mixture. Once he gets it back, Eric is planning to do a test flight. Doug is looking at his paint job, and while he knows that paint is an important protector, he’s trying to avoid a costly and invasive full repaint. Paul said you can absolutely go in and touch it up yourself. You can use a touch-up brush, sprayer, or anything you like. Colleen said that the vast majority of the work is in prep, and that the paint color will never match because the original paint will have faded. “Be careful and measured,” she said. Mike said to make sure the aluminum is clean and corrosion-free prior to applying the paint. Paul suggests Scotch Brite and Alumiprep (https://www.aircraftspruce.com/catalog/cspages/alumiprep.php) and Alodine (https://www.aircraftspruce.com/catalog/cspages/alodine1201.php) to make the primer stick. Get an automotive paint person to help blend the colors, he said. And Mike says to make sure you don’t sand through the thin layer of Alclad. Andy wonders if his IO-540 is running too cool. His cylinder head temperatures only top out at 310 degrees, which he's reading on an Electronics International engine monitor. Mike said EI makes two probes for their engine monitors, and the P-100 always reads low because there’s an air gap at the cylinder head probe that makes it artificially low. The only downside of running too cool is potential lead scavenging. Mike said to pull the spark plug and use a borescope to look at the exhaust valve stem. If there isn’t deposit build-up, then there’s nothing to worry about. But lots of lead means you have to somehow increase the temperature. Tom is worried about his compression readings. His O-320-D2G had a cylinder of 38/80 only 18 hours after overhaul. Two more cylinders are reading a little low now at 100 hours. He thinks all of them are leaking a bit, and have gotten slightly worse. He expects them to get to the low 60s, and he’s worried that when he wants to sell, buyers will baulk at the numbers. So he’s wondering if he should just replace the cylinders now so he never has to worry about it. The hosts all agree he is overanalyzing and should monitor as normal, keep flying, and work on the cylinders only when it’s required. Jeff has a Cessna 180 floatplane and a new fuel flow meter has him thinking. He’s wondering if the performance charts are based on tach time or clock time. Paul assumes that because the tach was the only instrument they had when they certified the airplane, it has to be tach based. “They had clocks when that airplane was built,” Colleen says. She and Mike are sure it’s clock time. Jeff also wonders why his float supplement shows fuel flow lower than the original handbook. With a difference of only .2 gallons per hour, Mike says they are effectively the same number, and not to worry about it.

You may think an annual inspection includes a verification of the accuracy of your fuel gauges, but you'd be wrong. Nor does the IA check the accuracy of your tach or any other number of instruments. This information comes to a pilot undergoing a first annual. Mike, Paul, and Colleen also tackle oil loss and temperature issues, why we stop our engines with the mixture, and the difference between a major and minor alteration. Submit your questions to [email protected] for a chance to be on the show. Full notes below: Chuck flies a 1941 Interstate Cadet with a Continental 85-8F engine. He had a prop strike four years ago, was inspected and got some new rings, gaskets, and a few other parts. He’s noticed he goes through a quart every four or five hours, compared to 15 hours prior to the overhaul. Mike suggests there may have been a problem when honing the cylinders, and Colleen suggests borescoping to see what the honing looks like now. Paul said a normal honing crosshatch is about 30 degrees, but that on a teardown they use a ball hone that doesn’t make a regular pattern. If it’s at all shiny it means they’re glazed. But ultimately they all agree it doesn’t matter and that it’s an acceptable amount of oil loss. Tom is a new mechanic who is looking for advice. A friend asked him to install a new stall warning horn to augment the stall warning light in his Cherokee. Paul suggests looking at a newer version of the airplane with a horn and a light, and submitting that information as approved data to the FAA. FAR 1.1 defines a major versus minor alteration. Advisory Circular 43-2B is acceptable methods for aircraft alterations, which Collen calls the bible of alterations. Mike makes the point that it’s a mechanic’s decision as to whether an alteration is major or minor. A major requires someone else’s signature, such as a field approval or FAA sign-off, while minor is only the mechanic’s signature. Jay flies a Mooney with M20F with an IO-360 with a JPI engine monitor. The oil temp probe is located near the first cylinder. On climb it hits 230F and trips the over-temp alarm. In cruise it stabilizes at 195F. The analog probe shows 30 degrees cooler. The hosts aren’t at all surprised that the probes are different. Colleen mentioned that when she changed engine monitors they moved the probe and her oil temps have gone down. Mike said our goal is to usually measure the oil temp at the coolest location. Peter has a Cardinal and is going through his first annual. He is wondering where the accountability is for previous mechanic oversights. His IA has found things like airworthiness directives that haven’t been complied with, a bucking bar left in the airplane, and so on. Mike makes the point that there is a difference between airworthiness discrepancies and things that are more discretional in nature. And all three hosts caution that each annual and pre-buy inspection are unique, and that it’s impossible to snag every discrepancy. Walter asks why we don’t just turn off the key when stopping a traditional piston airplane engine. The hosts agree that it is solely a safety consideration, and meant to get gas out of the system. That way an ungrounded mag can’t refire the engine and create a safety issue with the propeller. Rolf has a TB-20 with an IO-540 engine that’s never been overhauled and is trouble-free. Last year he noticed on the engine monitor traces that the number 1 and number 2 EGTs were very low at low fuel flow. His shop measured the dry tappet clearance and found the intake valves were well in excess of the limit. They were able to bring them within limits, but the EGTs are still bottoming out. Mike makes the point that the valve clearance limit is only to ensure that the amount of play in the system so that the hydraulic lifter can “take it up.” The hosts agree his engine is in fine shape, and not a safety issue. They do recommend he prepare for an overhaul in the future based on the symptoms.

This month Mike, Paul, and Colleen talk fluids. Danny has an oil leak, Steve has a fuel leak, and Jeff is puzzled by guidance on which oil to use. Plus, a question from a maintenance newbie, looking ahead to overhaul, seeing double on batteries, and a pesky propeller governor problem. Submit your question to [email protected] for a chance to be on the show. Full notes below: Dash has a T-34 and is wondering about the implications of having two 12-volt batteries in series, rather than one 24-volt battery. Paul says one battery is simpler and less costly to maintain, but two 12-volt batteries in series can generally push out more current. You can treat them as one 24-volt batteries and use the applicable trickle charger, Mike says. To do this you would take a 24-volt charger and treat them like one battery, Colleen says. Take the cables and hook up the positive from one battery and the negative from the other battery. They all cautioned to make sure not to hook anything to the short, stout cable connecting the two batteries. Dash also says a mechanic at his airport told him not to continuously charge the battery because it will reduce capacity, but the hosts say that’s bad advice and that a trickle charger can be on the batteries all the time. Danny has a continuously oily windshield on his Bonanza, which he thinks might be coming from the top of the case. The engine has 2,200 hours and looks great on the borescope, and he’s hoping an overhaul won't be necessary. Paul said he definitely wouldn’t pull an engine for this. He goes straight to the crankshaft seal as the offender. Mike thinks the o-ring that seals the prop to the flange is another good culprit to check. Mike said oil coming from the top of the case would go on the back baffles and other spots inside the baffles, not on the windshield. Chris has an O-540 on a Cherokee 6, and although the engine is still running strong, he’s planning ahead and wondering if a rebuilt or overhauled engine is better. Mike said this is the worst time he’s ever seen to do anything to an engine. Colleen said she thinks people are risk averse and she’s always overhauled engines and has been very happy. Mike said the only reason to go rebuilt is if you know you have to replace a major component or if you want to minimize downtime. Mahesh is looking for resources to become better acquainted with managing the maintenance on his Cirrus. The hosts recommend the Cirrus Owners and Pilots Association seminars, owner-assisted annuals, and Mike’s books https://www.amazon.com/dp/B08KHDPPWG?binding=kindle_edition&qid=1643661371&sr=8-4&ref=dbs_dp_rwt_sb_pc_tukn Sebastien and Tim have a Murphy Super Rebel with a governor problem. The propeller wanders 35 rpm up and down, and they’re wondering if it’s a problem and how to fix it. Colleen suggests checking the integrity of the rod end to the bell crank. Jeff has a Lancair and wants to switch oils, but Continental Service Information Letter 19-04 that says operators shouldn’t change oil until the engine is overhauled. The hosts all agree that this was a misguided document, and that switching oils will have no determinantal impact to the operation of the engine. Steve’s Piper Lance is weeping fuel and he is wondering how critical the problem is. His A&P said he could take the tanks out to have them resealed, but all agree that this isn’t necessary. Paul said the Piper maintenance manual and FAA maintenance advisory circular have a good chart to show the various fuel leaks and what to do about them. If it’s not leaking bad enough to pull the tanks he said it’s probably not worth doing anything. 

Mysterious metal in the filter, reporting an owner to the FAA, when to change ELT batteries, and the elusive perfect hot start. This month Mike, Paul, and Colleen handle some of the toughest questions in aircraft ownership. Submit yours to [email protected] for a chance to be on the show. Full episode notes: Brian asks how one is to know when the ELT battery runs for more than an hour or has reached 50 percent of its life. FAR 91.207 requires replacement on these conditions. Short answer: you don’t. The hosts point out that the batteries can’t be load tested and there’s no outside monitor to know how long they may have been active. So, if in doubt, replace them. Ryland wants to know if he can install a non-certified engine monitor in his certified airplane. Mike breaks down the decision tree that leads to an answer with an extreme example—installing a refrigerator in your airplane. You must show it meets the same certification requirements the aircraft had to meet. As Mike said, you have to jump through the same hoops that the manufacturer would have had to do had it decided to install one at the factory. First you must decide if it’s a major or minor alteration. A major requires approved data, which means getting an FAA field approval. If it’s a minor alteration the technician must make the determination that it meets all the applicable certification standards. Most difficult of which is that it doesn’t interfere with other systems in the airplane. Most mechanics won’t take it upon themselves to do that, he says. Colleen said she has gone through the field approval process and it’s quite difficult. Richard wonders if he’s damaging his engine by keeping the rpm below 800 on initial startup. He flies a Cessna Skylane with a Continental O-470. The hosts agree that Richard is overthinking this a bit and there’s no risk of damage at operating at such a low rpm. Mike said he would use roughness as the lower limit. Justin asks about his responsibility to report an unsafe aircraft to the FAA. After an alarming pre-buy inspection of an airplane he decided not to buy, he’s concerned another potential buyer may be at risk. Mike, Paul, and Colleen have strong feelings about this issue. Paul said a pre-buy isn’t an annual inspection, and it’s the owner’s responsibility to ensure airworthiness. This is the only person you should report the findings to, he said. As a follow-up Justin mentions an airplane he was asked to ferry that had a hole in the bottom of the wing. Mike explained the four entities responsible for airworthiness--the factory when the airplane is built, the owner, a mechanic one day a year at the annual, and most critically, the pilot in command. Tim asks aviation’s most difficult simple question—how do you consistently hot start a big bore fuel-injected engine? As a CFI his normal advice to clients is to use the technique that works best for you in your airplane. In his Cirrus Paul goes throttle and mixture forward, fuel pump on until the fuel pressure stabilizes, then everything back, throttle cracked, and mixture slowly increased while cranking the starter. He uses this for hot or cold starts. Mike suggests priming and cranking simultaneously. Paul mentions a technique of running the boost pump on high for at least 45 seconds while the mixture and throttle are at idle cut off, and then performing a normal start. This circulates cold fuel in from the tank. Jared is the maintenance officer of a flying club with a Cessna 172M. They’ve been finding metal in the oil filter that doesn’t look like that from normal sources. Lycoming couldn’t find it, and neither could the shop that did the overhaul 600 hours prior. The overhaul shop did warranty work, including replacing the crankshaft. It didn’t work. Jared had sent in photos and Mike didn’t think they looked like crankshaft issues. Paul thinks the oil pump is a strong suspect. But overall the hosts are stumped, and Jared promised to come back later with an update.

Ever wonder what you're looking for when you preflight a Cessna with those small oil doors? So did our caller this month. Mike, Paul, and Colleen also field questions about a burned valve, winterizing for cold-weather ops, how to do an in-flight magneto check, and whether you'd really run out of fuel before oil with a leak in the gauge line. Submit your questions to [email protected]

This month Mike, Paul, and Colleen dive into questions about valve failures, tracking engine times, aging engine accessories, and worrying cylinder head temperatures. Plus, a question that could only come from an instructor.

This month Mike, Paul, and Colleen tackle everything from radio gremlins to the big questions of aviation, such as an overall maintenance philosophy and the reliability of our aircraft. Send your questions to [email protected] for a chance to get on the show. And please take our survey to tell us how we're doing. You can find it at https://aopa.az1.qualtrics.com/jfe/form/SV_cZSqTKSpaOTVjdI?Referral=APS

This month Mike, Paul, and Colleen tackle questions big and small. A pilot wonders why aircraft engines are so expensive, a young student knows there must be a better way to clean an airplane, and owners tackle concerns over increasing compressions, throttle lag, and avionics. Send your questions to [email protected] And please tell all of us at AOPA how we're doing on podcasts. Take a short survey: https://aopa.az1.qualtrics.com/jfe/form/SV_cZSqTKSpaOTVjdI?Referral=APs

Broken rocker arms, metal shards in the valve cover, and oil in the cylinder, oh my. This month Mike, Paul, and Colleen focus on listener engine problems, give some guidance on mods for an experimental builder, and bust an oversquare myth. Submit your questions to [email protected]

A savvy owner wonders how to trust her airplane with no logbooks, a Cessna pilot is curious if he's getting all the power he paid for, and Mike, Paul, and Colleen tackle an unruly governor. Send your questions to [email protected]

This episode Mike, Paul, and Colleen debate shock cooling, help an owner set his stall warning tab, debunk unapproved equipment myths, give an owner advice on breaking in new cylinders, and more. Submit your questions to [email protected]

This month owners look to settle arguments with their mechanics over tire wear and avionics glitches, one pilot tries to determine myth from reality on keeping fuel tanks topped off, a pilot learns his oil pressure problem isn't a problem, and Mike, Paul, and Colleen describe why detonation is a self-correcting event. Submit your questions to [email protected]

This month Mike, Paul, and Colleen cover the basics of oil analysis, corrosion proofing, fuel selector play, how to pick an overhaul shop, and prop people. Send questions to [email protected].

This month Mike, Paul, and Colleen tackle a number of questions about oil. Where it should be, where it shouldn't be, and why it isn't where you last added it. Plus, a jet pilot is grounded by tires. 

This month Mike, Paul, and Colleen delve into must versus should. Must you open all those inspection ports, is the prop and governor overhaul mandatory, and should one owner retorque his cylinder after a re-installation mistake? Send your questions to [email protected]

This month Mike, Colleen, and Paul revisit sticky valves, diagnose shimmy dampers, give a bit of career advice, and talk about what right looks right on throttle response. Plus, silly pilot tricks with animals! Send your questions to [email protected]

Mike, Paul, and Colleen talk about why lean of peak if beneficial. Also, the hosts tackle questions on sticky valves, how to properly break in an engine, oil consumption, and more. 

Snake oil, cranky turbochargers, oil issues, camshaft rust, and more in this month's episode. Plus, a new owner tries to stump Mike, Paul, and Colleen on propeller rpm checks. 

Corroded control cables, the right oil for engine break in, pesky fouled plugs, and just how far can you push back on your annual. Paul, Mike, and Colleen handle all these topics and more in this month's episode. 

Checking an airplane for aerobatics, engine failures due to oil starvation, mysterious airplane vibrations, and why replacing cylinders could be a bad idea. Mike, Paul, and Colleen handle these topics and more in this month's episode.

New from AOPA, it's a podcast featuring you, the pilot and aircraft owner. Experts Mike Busch, Paul New, and Colleen Sterling answer your aviation maintenance questions. Subscribe today to catch all the episodes.