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. 21 H FA

    Being an aircraft owner is the hardest job in aviation

    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 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: 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.

    51 min

  2. 15 OTT

    That's an urban legend

    What's in our oil, how to keep cool (and warm), and lean of peak are on tap for this episode. 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: 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.

    50 min

  3. 1 OTT

    More time to fly, less time to turn wrenches

    In this episode, Mike, Paul, and Colleen discuss unnecessary maintenance, lean of peak, and flaming exhausts! 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: 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.

    49 min

  4. 17 SET

    You have a lot of splaining to do

    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 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 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.

    53 min

  5. 1 SET

    "Mechanics can be ornery sometimes"

    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 podcasts@aopa.org 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.

    57 min

  6. 22 AGO

    Live from Airventure 2025

    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 podcasts@aopa.org for a chance to get on the show. Join the world's largest aviation community at aopa.org/join

    45 min

  7. 1 AGO

    That'd be like putting grease on the road

    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 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: 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.

    1 h 2 min

  8. 15 LUG

    That's one way to flat spot a tire

    Mike, Paul, and Colleen explain why they almost never set their parking brakes. Plus, valve guide concerns and gotchas on preflight. Email podcasts@aopa.org 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.

    42 min
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Descrizione

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.

Informazioni

  • Creatore
    AOPA
  • Anni di attività
    2020 - 2025
  • Puntate
    92
  • Classificazione
    Contenuti adatti a tutti
  • Sito web del podcast
    Ask the A&Ps

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