Ask the A&Ps

A caller wants to know what they don't teach you in A&P school. Plus AD compliance, a scary engine failure, and putting the lean in lean of peak.

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KC wonders why ADs appear on some logbook entries as having been complied with with a terminating action, and in future entries the AD reappears. He discovered this was a common occurrence when he was looking through logbooks as he and a partner were purchasing an airplane. Mike said you can't tell from an AD compliance summary whether something has been permanently complied with. That is found in the logbook through some sort of permanent change, like a kit or STC. If some other IA signs off the AD compliance again it could be because the IA simply missed that the AD was permanently complied with. Paul said he always assumes an airplane he sees for the first time has errors in AD records compliance and he verifies everything himself. Paul said this often happens because the part was changed somewhere in the airplane's history to make it no longer permanently complied with.

Jeff is looking to fine-tune his lean of peak performance. He flies an RV-10 with an IO-540. He has a small window in lean of peak where he is running a bit rough, but if he runs more rich the CHTs will climb into the 360-degree range. Mike said Jeff is trying to run too cool. A Lycoming typically runs 20 degrees hotter than a Continental, so he said flying at 400 degrees CHT is perfect and nothing to worry about. Keeping it cooler won't necessarily matter.

Mark is going to A&P school on the side for additional enjoyment and greater involvement in his airplane maintenance. He is at a Part 147 school, and he feels like the education is good, but he's wondering what else he needs to know about GA maintenance. Paul explains that school is a great intro to the various topics, but it's not long enough to be detailed in all facets of aviation maintenance. Most specific learning is on the job training. Mike suggests Savvy's new IA renewal program, which anyone can take for free.

Frank has a turbocharged Rockwell Commander. The engine sputtered and stopped at 1,200 feet. He turned back to the runway and made it safely. His first thought was water, but none was found. The mechanic sent his magneto out but didn't find anything. Paul said it wouldn't be an ignition problem because both would have to fail or one would have to go badly mis-timed. A key piece of evidence is that the engine did end up restarting again on his approach to the runway. The hosts think it's fuel delivery. The electric boost pump was on. Mike suggests it was a stuck carb float. Paul said the engine will run on a similar engine for about 23 seconds with fuel just in the bowl.

Join Mike, Paul, and Colleen for a second live session from EAA AirVenture in Oshkosh 2026 as they are try to answer the audience's most pressing maintenance questions.

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Join Mike, Paul, and Colleen as they take questions live from the audience at the AOPA tent at EAA AirVenture 2026.

Which oil is best, where is the oil going, running lean of peak with a carb, and how to fly a turbo are on tap for this episode.

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Full episode notes below:

Chris' American Champion Super Decathlon has an oil consumption issue. While his engine was apart after a prop strike the cylinders were honed, and he broke it in properly. He has since replaced cylinders, broke it again, and is still only getting three hours per quart. He said oil is coming out of the fuel servo, which everyone has told him is normal, but the hosts quickly disagree. Mike suggests borescoping the back side of the intake valves and looking to see if one is oily. If it is, chances are the intake valve isn't seating properly and is being sucked back up and burned.

Chris is trying to run lean of peak with a carbureted engine. He has an O-360 and he wants to make sure he's not doing anything wrong. His technique is to lean to the point of roughness and enrichen only enough to smooth things out. Mike said that's a solid technique and that most four-cylinder carbureted Lycomings run well lean of peak because they have a good balanced mixture distribution. Mike said not to worry about how lean he is. If the temperatures are within limits and the engine is running smoothly, you are good.

James has a Piper Turbo Lance and he wants to make sure he is running it properly. His manual has a five-minute limitation on takeoff power, and he's wondering where that comes from. Paul said the older Cessna 210s have a five-minute limit at 2,700 rpm, and they discovered that the limit was all about noise, and not about the health of the engine. They told James to check section 2 of his POH, limitations, which would require the procedure regardless of the reason.

Mason uses Aeroshell 100 plus Cam Guard. He's heard that straight weight oil remains on engine parts longer during periods of mis-use. But he read that Aviation Consumer tested oils and that corrosion protection was more correlated to added chemistry than viscosity. He's wondering if there's data to support either position. Mike said he'll recommend a multigrade for pilots who operate in a variety of temperatures. Mike things the cleanliness probably has more to do with Cam Guard use and operating lean of peak.

A fidgety fuel problem, octane ratings, and water in the oil are on tap for this episode. Email podcasts@aopa.org for a chance to be on the show.

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Full notes below:

Gareth has a turbo Arrow and he's been fighting a problem with fluctuation fuel flow. Sometimes the engine quits on the ground or runs rough in the air. They've checked the fuel spider, fixed intake leaks, overhauled the fuel pump, an exhaust leak, and much more. Paul is convinced that air is entering the system or there is a vapor issue. He suggests checking the heat shields near hot parts of the engine, etc. Mike suggests that it could be related to upper deck pressure, which controls the aneroid in the fuel pump.

Matt wonders if fuel octane impacts timing. He has a Cessna 150 and is running autogas, and he's wondering if his ignition timing should be changed to accommodate a difference in octane. Paul said the airplane was certified with 80 octane, so it's fine to keep the timing as it is.

Scott is wondering about an alternative to safety wire. A company called Bergen makes a safety wire alternative and he's wondering if it's legal to use on FAA certified airplanes. Mike said even if the company doesn't say it's FAA certified that it would almost certainly be a minor alteration, and therefore at the discretion of the installing mechanic. Paul uses them in certain applications and likes them.

Scott has a IO-540 on a Socata Trinidad and was about to overhaul his engine, but found Mike's maintenance philosophy. He's now at 2,300 hours and counting. Everything looks good except that water occasionally shows up in his oil analysis, and he's struck out finding help through his mechanic. The water is a byproduct of the combustion process. When you shut down the crankcase is full of steam, and that steam then condenses into water. You can help keep that water down by taking off the oil cap after shutting down, or by hooking up an engine dehumidifier. Scott flies about 100 hours a year evenly spread out, and he lives in a dry environment, so the hosts agree the dehumidifier probably isn't necessary.