Ask the A&Ps

By AOPAEducation Leisure How To

Ranking
32nd
on How To
Favorites
85
Followers
Typical duration
56 min
per episode
If it hooks
65%
finish an episode

Based on Podcast App listening data

Ask the A&Ps episodes

May 15 "TBO is not a reason to do anything to an engine"
Rising temperatures, unnecessary overhauls, unusual rigging, and ancient cloth in the wheel well are featured. Email [email protected] for a chance to get on the show.
Join the world's largest aviation community at aopa.org/join

58 min
May 01 "If you lose a cylinder in your Cessna 150 you are down on a road somewhere"
Sticky valves, sleepy valves, and valves destined for the trash are on tap this episode. Email [email protected] for a chance to get on the show.
Join the world's largest aviation community at aopa.org/join
Full episode notes below:
Mac is trying to get a cylinder to wake up on his Piper Lance. The engine ran rough, and a magneto clearing procedure didn't help. The number 5 cylinder was dropping off according to the engine monitor. It's also next to the turbocharging exhaust. His A&P thought maybe the injector line being next to the pipe might be causing a problem. It only happens after landing, not while flying. Paul thinks it would be a more widespread issue if the plumbing engineering were the issue. The aux fuel pump stops it from happening. Mike suggests a mixture that's too lean could cause this. They suggest checking the idle mixture rise on shutdown. The rpm should rise 25-50 when pulling the mixture at idle. If it doesn't rise as much it's too lean, and if it rises too much it's too rich. They also suggest running a GAMI lean test to determine if the cylinder is a lean outlier.
Conor has a Cessna 150. On the way back from Oshkosh last year he experienced a stuck valve. There was discoloration from being hot when the cylinder was pulled. He leans aggressively. He's wondering if he's leaning too aggressively and is getting the engine too hot. He leans to roughness and enrichens only until it gets smooth. The hosts think the engine has to be in detonation for it to get too hot. The piston tops are fine under borescope, so the hosts think it's fine.
Andrew wants to knock the rust off his A&P certificate. The hosts suggest the new Savvy Aviation IA recurrent course. It's a free 8-hour course to help refresh his memory. Beyond that, Paul suggests a 172 course, which is the airplane he plans on buying. There really isn't a hands-on refresher course, according to Colleen. She suggests he could hire an A&P and work alongside him or her to brush up. He could also take an LSA repairman course, which is shorter than a typical A&P course.
James is asking about the right time to overhaul an engine. He is in a club with a Diamond that flies about 500 hours a year. When he wrote in there were 1,900 hours on the engine. They were told the turnaround would be three months. They decided to order a reman from Lycoming, which was scheduled to take 15 months. Then they got a notice that it would be an additional 12 months. It ended up only being 17 months. Their club decided that more than three months of downtime wasn't acceptable. If the lead time for engines is more than a year, so how do you listen to the engine when the delay is so long. Paul said you buy consumables, like cylinders. Cylinders can sit on the shelf for a long time.
51 min
April 15 "Am I doing anything evil?"
Avoiding maintenance can be a good thing when what's recommended is unnecessary.
Email [email protected] for a chance to get on the show.
Join the world's largest aviation community at aopa.org/join
Full notes below:
Dominick is questioning his mechanic's advice on prop overhauls. He has a Cessna 310 and his left rpm is too low on approach when the control is full forward. It's not an issue on the ground or on takeoff. His mechanic recommends overhauling the propeller, and since he's doing one he should do both. He swapped governors and that didn't change anything. He sent the prop back for IRAN and they didn't find anything significant. Paul suggests it's the low pitch stops. This is a classic twin owner trap, Mike says. The two engines are never the same. Everyone agrees that he can leave it as is.
Vas has an RV-10 and the Lycoming IO-540 has been acting up. During some flight training in the airplane, he noticed oil consumption went up, metal was in the filter, and he ended up overhauling the engine. He's wondering if he should have just pulled a cylinder instead. He was flying 140 hours a year, and he's wondering why he would get corrosion. Higher oil consumption isn't a corrosion problem, but the cam and lifter spalding do indicate it. These were unrelated problems, according to Mike. Paul thinks it's possible the damage was already in place when there was a previous IRAN. They settle on it being a lifter hardening issue, meaning poorly manufactured parts.
Jim has a Mooney M20K and an instructor showed him a leaning procedure while in cruise at 9,000 feet. They set the manifold pressure to 30 inches, the RPM at 2300, and then pulled the fuel back to 11 gph. That's how he's been leaning ever since. CHTs are in the 360/370-degree range. He trails the cowl flaps to try and cool the CHTs if it's a hot summer day. If the TIT gets too high he'll enrichen it just a touch. Paul said if he adds more fuel and the TIT goes down, he's running rich of peak.
Peter found some residue on the top of his intake valves on the engine on his 172N. He typically flies with autogas. He's wondering if can or should get rid of it, and if so, how to do it. Paul said people talk about it, but he's never done it. They suppose it's not carbon, but probably coked oil. They suggest a wobble test if he's really worried, but generally they think he can leave it alone.
58 min
April 01 "That installation is fraught with peril"
How much should a mechanic tell a client during an annual? Mike, Paul, and Colleen handle this question and more.
Email [email protected] for a chance to get on the show.
Join the world's largest aviation community at aopa.org/join
Full notes below:

Justin flies a Twin Bonanza and cylinder 5 on his left engine takes as much as a minute to fire up and start running. It comes online fastest if he goes very lean quickly after starting. He's pulled the valve cover and springs off, and it's not a sticky valve, and he's reamed the valve guides. Mike wonders if it could be a primer problem. Justin disconnected the primer line, ran the boost pump, and checked for leakage and couldn't find any. Paul suggests taking the line off, capping off the injector, and then trying it.
Jorg is trying to make sense of his data. He has a K35 in Austria and he has GAMI injectors and an engine monitor on his IO-470. He has a low CHT on the number 6 cylinder, and it's the first one to go on the lean side, and it shuts down first if they go very lean. An induction leak test seemed fine, and his GAMI spread is less than a gallon an hour. The valve was also lapped. Mike said a low probability culprit could be if the bleed air holes in the injector nozzle were plugged, since they don't seem to have an impact at wide open throttle, but would at a reduced throttle.
Mark saw a Youtube video and is now wondering if there's danger lurking in the alternator. The video mentioned how an alternator elastomer coupler failure could lead to a catastrophic engine failure. Paul said the installation is critical because of some critical components. Mike thinks the video relies on old information. He said Continental used to employ a spring, which would come apart and throw large chunks of metal into the engine. The coupler is meant in part to protect the engine if the alternator seized, but sometimes the coupler would fail and cause its own failure. The newer versions have an elastic or rubber piece instead of a steel spring, which shouldn't cause an engine failure.
Chaz is an A&P/IA and he wants the team to weigh in on the debate as to whether the inspector should give pilots a full list of squawks or only the airworthiness issues. He personally thinks he should give the whole list so the owner knows where he stands. The hosts agree that the full list is preferable. The mechanic is giving a full slate of options, and not a required list. Airworthiness items can be listed separately or be flagged.
54 min
March 15 "I'm an old mechanic and really like the idea of priming and painting"
Quick corrosion, long-lasting engines, and mobility mods are on tap for this episode.
Email [email protected] for a chance to get on the show.
Join the world's largest aviation community at aopa.org/join
Full episode notes below:
Patrick is looking for the right fit on a potential aircraft purchase. He had a shoulder replacement and lost some mobility in his right shoulder. He’s wondering if he could get an accommodation on things like flap controls. Paul suggests he look for an older Cessna with the progressive flap switch, not the one with pre-selected detents. The hosts thing that up/down progressive switch would be a minor alteration and just a
few wires. The pre-select flap lever is probably a major alteration and a lot
of work because there’s a lot going on behind the panel.

Jeff has a Maule M7 on floats and is battling corrosion. Recently he did a salt water landing, sat for about 3 hours in the water, flew home, and his left main gear didn’t rotate as he landed. He saw that the main forks had a bloom of corrosion that froze the wheel. He washed everything in fresh water, and then next day saw a bloom on the other gear as well. He is wondering if he had a stray current given how quickly it developed. Mike thinks it’s unlikely because if the battery if off it’s completely isolated from the rest of the system, meaning their shouldn’t be a way for the battery to provide electrical current anywhere on the airframe.

Lindsay recently purchased a Piper Lance and wants to make sure she keeps the engine going as long as she can. They go over the basics and make sure she is boroscoping the cylinders, fly it regularly, etc.

Mark is wondering how soon is too soon to put in cowl plugs after flying. He has a Cessna 206 and he’s wondering if he can put in the cowl plugs right away. The concern is about the plugs, not the engine, Paul said. The hosts all agree that he's fine to seal the cowl off as soon as he likes.
50 min
March 01 "That's an oft-reported myth"
Is going past TBO more expensive? Plus fuel vents and turbocharger temps. Email [email protected] for a chance to get on the show.
Join the world's largest aviation community at aopa.org/join
Full episode notes below:

Mike wonders if running past TBO actually costs more. He has
a Mooney and has heard that overhauls far beyond TBO can cost more as a result
of having to replace more parts. That is an oft-reported myth, Mike says. The
only things that can cause an up charge on most field overhauls are having to
replace the case or the crankshaft. Otherwise it’s a fixed price. Paul says the
top engine generally goes into the trash. On the crankshaft, they usually just
have to polish it or grind it. There’s no repairing a crankshaft. If it’s bad,
it was bad because it had some other type of problem. You can go thousands of
hours on crankshafts. Mike said Lycoming had a white paper on their website
that said crankshafts are generally good for 14,000 hours. Cracks on the case can
be welded.

Mark has an early 182 and he’s having issues with the fuel
caps properly venting. He has noticed that once you fill the tanks with cold
fuel, there doesn’t appear to be an outflow vent. Paul said there’s a small
weep hole that allows the expanded fuel to vent. But Mark’s tanks still aren’t
venting. He pulled it out but didn’t seem to find a weep hole. He said it looks
original and has an early Cessna part number. If the fuel is pouring out it
needs to be replaced because the check valve is bad. The wing will balloon and
can cause structural damage without a weep hole. He said when he removes the
cap a big woosh of air will come out, indicating the fuel isn’t venting out as
it expands.

Jim is wondering how TIT and EGT intersect. He flies a turbo
Saratoga and has been experimenting lean of peak and rich of peak. He’s noticed
a significant difference between EGT and TIT. If the TIT is farther away from
the engine, he’s wondering why it’s hotter than EGT. He’s also wondering how
hot he can let the turbocharger get. Mike said TIT is hotter because the EGT
probe is only seeing gas flow for less than a third of the time, and only when
the exhaust valve is open. The EGT probe actually measures a “probe”
temperature that averages the temps over time. When the gas gets to the TIT
probe it’s a constant heat from all cylinders all the time. Redline on his TIT
is 1,650 degrees, which Mike said is a continuous operation limit. Paul asked
what the exhaust system is made of because that matters. He suggests not
exceeding the red line. In cruise, the lower you can keep the TITs, the longer
the system will last. Mike limits his TIT to 1,600.

50 min
February 15 “Is this like pulling a mattress tag off?”
What exactly should we be looking for in our cylinders? Plus torque tales, making TBO, and overzealous manufacturers.
Email [email protected] for a chance to get on the show.
Join the world's largest aviation community at aopa.org/join
Full show notes below:
Jared asks what he should be looking for with his borescope. He’s seen bad valves and what that looks like, but he’s also hoping to see what bad scoring and other things. Colleen stresses to focus on what goes wrong with a cylinder, and being able to identify those attributes. Things like broken rings, piston pins, detonation signature, etc are identifiable, and can be examined. Paul said rust is always something to look for, but most cylinders have some. Knowing how much and why it’s there is what matters. Mike said rust would cause him to consider the camshaft on an airplane in a pre-buy situation, for example.

Chad has a new Cessna turbo 206. He wants to be sure to get to TBO and then some. Paul said the one thing he needs to do is fly as often as possible. He is flying 400 hours a year, which the hosts love. He asks if he
can fly a maximum continuous power, and the hosts agree that he can, so long as his cylinder head temperatures are within spec. The book tells Chad to lean to peak turbine inlet temperature, and not to run lean of peak. He wants to know if this is a real threat or a hollow one. Once again, the hosts agree that it’s a hollow threat, and that he should operate lean of peak if he can. They also discuss the myth of turbo cooldowns. Mike said George Braly instrumented a turbo and found that it actually got hotter as it sat on the ramp “cooling down.”

Serrhel is sick of the Continental maintenance schedule. He has a Cirrus that is under warranty, and he’s required to do the maintenance as scheduled. At 300 hours an injector cleaning was required, and only a few
months later, the injectors had to be cleaned again during the annual. Cirrus and Continental required it, even after some pushback. Paul said manufacturers don’t buy into the probability of maintenance induced failures or in the concept of reliability centered maintenance. The discuss the reasons why manufacturers think this way, and Mike said a conversation with a factory representative taught him that they basically don’t trust GA pilots and owners to maintain aircraft at a high level.

Patrick is throwing down a challenge to Paul. He said Paul always stresses that when tightening case through-bolts, you torque simultaneously with torque wrenches on both sides at the same time. Old Continental videos say the same, but the video shows the technicians only torquing on one side at a time. Despite the guidance, Paul said it doesn’t make sense to put a torque wrench on both sides at the same time. Mike said if you put a torque wrench on both sides, one side will be torqued dry and hit the pre-load spec too early. Mike and Paul then get into a debate about how the logbook entry should be made when if you decide not to follow Continental’s advice. Patrick further mentions that the Continental service manual doesn’t say it should be simultaneously.
55 min
February 04 "The owner can't do maintenance because the owner doesn't have arms"
The definitive guide to owner maintenance, slipping starter adapters, and close CHT tolerances.
Email [email protected] for a chance to get on the show.
Join the world's largest aviation community at aopa.org/join
51 min
January 15 "You're going to give him nightmares"
Creative leaning techniques, rusty cylinders, and odd manifold pressure indications are on tap this time.
Send your questions to [email protected] for a chance to get on the show.
Join the world's largest aviation community at aopa.org/join
57 min
January 01 "He has a piston with a smiley face on it that's not very happy"
Old engines, rusty airplanes, and a strange valve incident are the puzzlers for Mike, Paul, and Colleen this episode. Send your questions to [email protected] for a chance to get on the show.
Join the world's largest aviation community at aopa.org/join
Full episode notes below:
John has a Beech Musketeer who had an unusual situation with his valve. The valve seat separated from the cylinder barrel and dropped down, striking the piston crown. He's wondering if he did anything to cause this, despite never exceeding 425 degrees CHT. The hosts agree that it was probably a manufacturing error, even though the cylinder had a few hundred hours on it. Mike said the only way this can happen is with a manufacturing problem or a high heat event.

Larry has an early SR22 with 3,300 hours on the engine. It's not in need of an overhaul now, but Larry has read those early SR22 cases are more robust, and he's wondering when the time comes if he should overhaul or do a factory reman. The hosts aren't aware of any particular issues that make cases from that generation better, but they do offer some sound advice on the reman versus overhaul question. Mike said that if the engine has been treating him well that Larry should overhaul it. And if it's been a lemon, send it off and get a new one from the factory. Larry is a little worried about resale, since people are skiddish with high-time engines. Mike suggests that an airplane with run-out engines is the best investment because it's been fully depreciated. Any additional time is essentially free.

Terry has been looking for a 182 and he saw one in California with corrosion. He wonders how much corrosion is too much. Paul said that according to Terry's photos, he wouldn't think twice about buying the airplane. The general rule is that you can take off only 10 percent of a structure and not worry about it. The skin on top of the wing where the corrosion can be seen is only 25 thousandth of an inch, which means you could only take off 2.5 thousandth of an inch and still use that skin. White splotching can be seen in the photos, and Paul said it's common for airplanes of that vintage, and not to repair it. Instead, he recommends spraying it with ACF-50 or Corrosion-X every few years. Doing so will stop the spread and not allow any further damage.
43 min

About Ask the A&Ps

From the publisher's feed

Experts Mike Busch, Paul New, and Colleen Sterling answer your toughest aviation maintenance questions. Submit questions to [email protected]. New episodes are released the first and fifteenth of…