Ask the A&Ps

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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. HACE 3 DÍAS

    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

  2. 17 SEP

    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

  3. 1 SEP

    "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

  4. 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

  5. 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 y 2 min

  6. 15 JUL

    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

  7. 1 JUL

    An airplane with no engine is worth nothing

    Oil is everywhere this time, with consumption and temperatures problems for three of our owners. 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: 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.

    1 h y 1 min

  8. 15 JUN

    You have to cart mogas around like a homeless person

    A Cirrus with fluctuating fuel flow, de-injecting an engine, and fear of overhaul 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 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.

    1 h y 3 min
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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.

Información

  • Creador
    AOPA
  • Años de actividad
    2020 - 2025
  • Episodios
    90
  • Clasificación
    Apto
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    Ask the A&Ps

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