Ask the A&Ps

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.

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.

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.

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.

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.

An owner wants to fly his engine after it sat for 7 years. Plus, prop strike at the shop, lean of peak, and break-in trouble. 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: Rupert is having trouble breaking in his new cylinders. They have five hours and the temperatures are still trying to go above 420 degrees on departure. They’ve checked fuel flow and baffling. In a twist of irony he is causing his cylinders to run too hot because the break-in is being prolonged because he won’t run the engine hard enough. Paul said Comanche’s have notoriously have poor baffling, which can also compound the problem. They recommend running it hard for a few hours and not to worry about the temps being around 420. Craig has a Pitts that was damaged on a high-power run-up after his annual. The tail came up and hit the prop. He’s wondering if there’s something else they should inspect since the case is going to be open. His crank is subject to an AD. The associated service bulletin requires replacement if the case is opened, but the AD does not. He said the insurance has agreed to replace the crankshaft anyway. They said other than close cylinder inspections, it sounds like he’s fully covered. Larry was finding that the lean of peak indication on his Dynon would show that he was lean of peak before the cylinders were actually there. He found a short paragraph in the manual that says if he changes the horsepower percent rating, it works fine. He also describes a procedure in the Dynon that basically recreates the GAMI lean test. Mike describes how Savvy does the AI engine modeling. The amount of air or fuel going into the engine will be the limiting power factor. In rich of peak, fuel is abundant, so air is the limiting factor. In lean of peak, fuel is the limiting factor. Dave last ran his engine 7 years ago. He mixed oil and camgard, put it into a pressurized tank, and sprayed it under pressure into every place he could. He’s changed desiccant plugs, and had a dehumidifier running as well. If he has pitting he’s wondering if it’s dangerous to fly. Paul said airplanes don’t fall out of the sky because of pitting on the camshaft, and Mike added that they do fall out of the sky after taking off cylinders to look for signs of corrosion. Either the engine will make metal in the filter or it won’t, he said. If the filter is clean for the next 100 hours he dodged a bullet. Nothing that could be wrong corrosion wise is a safety of flight item. It’s a safety of wallet item. Paul said he would recommend changing the oil soon after running it. If the cylinders don’t look corroded the bottom end probably isn’t either, Mike said. Paul suggests he crank the engine with one set of plugs inoperative until he gets an oil pressure indication, and then start it normally.

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.