Ask the A&Ps

De: AOPA
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  • Resumen

  • 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.
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Episodios
  • "My airplane is a flying experiment"

    "My airplane is a flying experiment"
    May 1 2025
    It's all engines all the time this episode. Rusty ones, sticky ones, and one that doesn't burn oil. Email podcasts@aopa.org 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.
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    1 h y 6 m
  • "They put all their maintenance records on napkins"

    "They put all their maintenance records on napkins"
    Apr 15 2025
    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.
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    1 h y 2 m
  • "Keep torturing those airplanes...and students"

    "Keep torturing those airplanes...and students"
    Apr 1 2025
    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.
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    55 m
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Great Information

I enjoy the varied questions and the discussions regarding the issues. I have learned a lot.

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Highly appreciate your show!

Excellent information since I am just a brand new power plant and soon to be airframe mechanic there’s so much to learn what is not being taught at schools and some very good information has been gained from your show thank you.

I look forward to your next podcast.

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Binged and listened to the whole series

I binged through the whole series. I am a gearhead and the family fixit guy. I love car shows, and this aviation themed podcast definitely has appealed to me. Even if you don't normally indulge in aviation activities, I suggest giving this podcast a listen. I think it will have cross appeal for many with other interests. please

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Wonderful podcast. Learned so much in just the first few episodes!

Wonderful podcast. Learned so much in just the first few episodes! Highly recommend it to anyone!

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