Ask the A&Ps

AOPA

Experts Mike Busch, Paul New, and Colleen Sterling answer your toughest aviation maintenance questions. Submit questions to podcasts@aopa.org. New episodes are released the first and fifteenth of every month.

  1. 9 HR AGO

    That's an oft-reported myth

    Is going past TBO more expensive? Plus fuel vents and turbocharger temps. Email podcasts@aopa.org 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 TITs, the longer the system will last. Mike limits his TIT to 1,600.

    49 min

  2. 15 FEB

    Is this like pulling a mattress tag off?

    What exactly should we be looking for in our cylinders? Plus torque tales, making TBO, and overzealous manufacturers. Email podcasts@aopa.org 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.

    55 min

  3. 4 FEB

    The owner can't do maintenance because the owner doesn't have arms

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

    50 min

  4. 15 JAN

    You're going to give him nightmares

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

    56 min

  5. 1 JAN

    He has a piston with a smiley face on it that's not very happy

    Old engines, rusty airplanes, and a strange valve incident are the puzzlers for Mike, Paul, and Colleen this episode. Send your questions to podcasts@aopa.org 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.

    43 min

  6. 15/12/2025

    Just be sure you lube it with something

    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 podcasts@aopa.org 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.

    44 min

  7. 01/12/2025

    If you go to 76 percent, the wings will fall off

    A creative modification, lean of peak with turbocharging, electronic ignition, and oil leaks are on tap. Email podcasts@aopa.org 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 TITs 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.

    51 min

  8. 15/11/2025

    It's one of the few accidents where you get to choose where it happens

    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 podcast@aopa.org 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.

    52 min
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About

Experts Mike Busch, Paul New, and Colleen Sterling answer your toughest aviation maintenance questions. Submit questions to podcasts@aopa.org. New episodes are released the first and fifteenth of every month.

Information

  • Creator
    AOPA
  • Years Active
    2020 - 2026
  • Episodes
    100
  • Rating
    Clean
  • Show Website
    Ask the A&Ps

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