Ask the A&Ps AOPA

This month Mike, Paul, and Colleen cover the basics. An owner wants to know if he should pull the throttle or propeller first in a climb, another wonders what the ideal power setting is for the run-up. Plus, mis-fueling and tired turbos. Email podcasts@aopa.org for a chance to be on the show.
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Full show notes below:

John has a 210 and wants the definitive answer on whether to pull back the power or prop first. Paul said he has a 5-minute restriction on full power. He suggests after 1,000 feet, reduce the rpm only to 2600 rpm. Then reduce the mixture in the climb to maintain the exhaust gas temperature that was roughly at takeoff. Then when he gets to cruise he can set the rpm where he wants. But leave the throttle wide open all the time. Paul sets the rpm where the engine runs smoothest. After the mixture and prop are set, then he can go lean of peak. Mike said lean of peak is usually most effective at lower rpm.

Ingram bought a Diamond DA-40 with the Austro engine and he’s worried about mis-fueling. The POH isn’t helpful because it only says to drain and flush the tanks if mis-fueling is suspected. The hosts aren’t aware of a test kit that ensures he gets jet fuel, so they recommend smelling the fuel sample because avgas and jet fuel smell much different.

Justin wants to know whether to believe his instructor and general guidance, or the manual. He said he was taught to do the run-up at 1,800 rpm, but the engine manual for his airplane said to run it up at 50 to 65 percent power. Mike said it’s better to run the engine up lean, and that 1,800 is perfectly fine. Without proper cooling, he worries about engine wear with regular high-power run-ups.

Royal is wondering if the turbo in his TR182 is losing it’s oomph flying higher. Paul said the fact that it’s turbonormalized means it lasts longer. The waste gate on his system is open until he gets much higher than most. Mike said turbochargers generally don’t lose power. It’s more likely the throttle linkage has changed over the many years that he’s owned the airplane. Paul said cam lobe wear can also be an issue. 

This episode Mike, Paul, and Colleen tell a flight school owner not to throw away a perfectly good engine. Plus, the origins of the annual inspection, safety wire, and poor engine monitor guidance. Email podcasts@aopa.org for a chance to get on the show.
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Full notes below:
Mike has a Cessna 150 with a bunch of advanced avionics, including a Garmin GI275 as primary engine instrumentation. The oil temperature setting frustrates him because it’s flashing cautionary at 200 degrees and warning at 210 degrees. The POH says the max is 240 degrees. Paul said the engine monitor should match the original gauge, so if there wasn’t a cautionary range on the original there shouldn’t be one on the electronic instrument.

David is challenging the maintenance norms. He’s wondering how the FAA originally came up with the idea and time frame of the annual inspection. Mike thinks it’s arbitrary because some things should go less than a year, and some can go much longer. Firewall forward and wheels and brakes should probably be less than a year, but things like cable tensions could go less. The phased inspections that turbines go through is more logical, he thinks.

The airplane in Albert’s flight school is difficult to start, and his mechanics can’t figure out why. They’ve looked at spark plugs, adjusted the fuel, fuel servo, magnetos, and more. They recommended replacing the engine next. Don’t do that, the hosts say. Mike asks for the starting procedure. In Albert’s write up he mentioned having to wait some time prior to trying to start again. Mike said the only way that would happen is if the engine is continuously flooded during starts. Paul said if there’s leakage in the flow divider, the engine can become overprimed because its as if it is being continually primed. Colleen said it’s not a bad idea to check the ignition harness and other electrical components. And Paul said to also look at the P-leads.

Slavic is learning to fly helicopters and he was surprised to find that none of the oil filters were safety wired, and he wants to know if it’s safe. The hosts are shocked. However, a safety bulletin from Robinson says that it’s not required. 

This episode a perspective owner wonders about the cost of tying down outside. Plus fuel pump problems, major versus minor, and more. Email podcasts@aopa.org for a chance to be on the show.
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Full notes below:
Steve’s primer in his Saratoga sat for a long time and was pumping air when he came back to fly it. He had to track a fitting to get it to pump fuel again. Paul thought that since the pump is lower than the level of the fuel tank, then it should have probably been ok with the long break from flying. He suggested that air had gotten in the system somewhere other than the pump. Although the problem hasn’t re-occurred, he wants to be sure there aren’t underlying problems. The hosts think since there aren’t any stains from leaking fuel that he probably doesn’t have an issue.

Dennis is looking to buy an airplane and he’s trying to establish the maintenance costs difference between having a hangar and being on a tie-down. They recommended a cabin cover to try and keep the water and UV out of the interior. Dennis is worried about the freeze-thaw cycle during his cold winters, but the hosts aren’t concerned. Paul said not to worry about all the snow that sits on airplanes during the winter either. Dennis asks about glass versus steam, and they suggest that maybe glass would fare better in cold weather.

Mark wants to install an air conditioner as a minor alteration in an Aerostar. He and the hosts talk in detail about the challenging issue of minor versus major alterations and what’s involved in that decision. Mark’s concern is that the air conditioner should have a few operating recommendations about usage, recharge, and so on, and he is worried about pushing into the major category. Adding limitations and a flight manual supplement would do that, but the hosts think he could legally offer operating suggestions that don’t cross into limitations.

Andrew works at a flight school with some airplanes have that airspeed in knots and some in miles per hour, and he is looking for a way to make life easier for his students. They discuss the issues involved with glass displays that are incorrectly labeled, and what that does to the legality of the airplane. Mike thinks so long as the original backup instrument is still legal that is probably ok. 

Is there a limit to how much oil consumption is too much? This episode, Mike, Paul, and Colleen answer this important question. Email podcasts@aopa.org for a chance to get on the show.
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Full notes below:
Jim has a Cardinal with 3,000 hours on the engine. Everything looks good, except that the oil consumption has increased substantially. They tried the ring flush procedure, and saw the fluid coming out of the carb intake and exhaust manifold. The second cylinder took an immense amount of effort to pull the prop through. They took that cylinder off, and found that the oil control ring had a lot of crud. Mike said he wouldn’t get too invasive in order to solve the problem. It’s not a safety of flight issue. They suggest replacing the cylinders only if the oil consumption bothers Jim and his partner. Jim’s partner suggested also overhauling the bottom end with cylinder changes. They advise against it, instead looking at the cam when the cylinders are off. Mike wonders if the ring flush was done wrong. None of the fluid should come out of the exhaust or carb. He and Paul said they’ve never seen fluid come out of the valves. They recommend trying again.
Nicolas and his partner disagree on how often they should change the oil on their Grumman Tiger. His partner wants to change the oil before the winter, when they usually only fly a few hours, and then again in the spring, when they fly around 30 hours. Mike said the oil change intervals are inexact. As the airplane is flown, the oil gets increasingly corrosive. He suggests not letting the airplane sit with old oil throughout the winter. So that’s when he would change it. He’s wondering if he can avoid changing the oil in the spring after only flying for seven hours over the winter. The hosts agree that it’s probably fine not to change the oil at that point. They recommend also getting a dehydrator to keep the inside of the engine dry.
John has a twin Cessna with one engine that quits when it’s cold. Mike said the fuel pressure at low rpm isn’t high enough. Or the idle mixture isn’t rich enough, or there’s something wrong with the flow divider. The easiest and cheapest thing to do is to adjust the fuel pressure or the idle mixture on the fuel control unit. Paul said his Cirrus does the same thing in winter. He thinks it’s the fuel divider.
Cheryl has a Skycatcher with a window tint and she is concerned about its legality, and whether it should be noted in the airframe logbook. So long as it doesn’t inhibit the view, the hosts think it’s fine. 

Can you fly a turbocharged airplane lean of peak? Absolutely! This episode, Mike, Paul, and Colleen describe how to do it. Email podcasts@aopa.org for a chance to get on the show.
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Full notes below.

Mike flies a turbo 206 and a 421 and is trying to fly lean of peak but the airplanes are running a bit rough. He wonders if there are tricks on turbocharged engines. The GAMI spread is half a gallon, so that’s not an issue. Paul said to start by getting the magneto timing really close and gap the spark plugs very tight. Mike said he might be trying to keep the cylinders too cool, which would make it run rougher. He recommends targeting 400 or 410 degrees on the Lycoming engines.

Adam read Mike’s column in AOPA PILOT about LSA viability when the manufacturer goes out of business. He’s been interested in buying an LSA, but the story gave him pause. The FAA wants nothing to do with LSAs, Mike said. The hosts then discuss the differences between certification and ASTM acceptance, and what it means to potential owners.

Garhett has had a bunch of maintenance-related failures, and it has prompted him to be more involved in his airplane’s maintenance. He’s now wondering the best way to obtain his A&P certificate. Paul suggests he should start by reading the FAA manuals. It took Mike 10 years to amass the required hours by working on his own airplanes under supervision. Short of going to school or getting a job as an apprentice, this is the best route. They then discuss creative ways to build experience.

Victoria wonders how to keep the family airplane clean when the airport doesn’t allow water to be used. Mike and Paul suggest flying somewhere else and washing it. Colleen said she would use water or cleaner wax from a spray bottle. Paul really likes Crazy Clean, but cautions against using anything other than water during pollen season. For windshields, Paul said Cessna recommends a lot of water, Dawn, and your hand. Definitely don’t use power tools, they say. 

A light oil mist on his windscreen has one caller concerned he needs to split the case. Plus, Mike, Paul, and Colleen tackle cold cabins, tire changes, and horsepower calculations. Email podcasts@aopa.org for a chance to get on the show.
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Full notes below:
Grant has a Mooney M20F and he’s seeing a light mist of oil on the windscreen after flying. His mechanic thought it was coming from a case bolt, which he re-torqued. That didn’t solve the problem, and the mechanic said the proper way to fix it would be to split the case, which Grant doesn’t want to do. Paul said that’s not the problem anyway. He said misting oil on the windscreen is almost always the crankshaft seal or the prop o-ring, both which should be fixed together. The parts are cheap, and the job is relatively easy. Colleen just did this on her airplane and describes the process.

Joe’s kids are freezing in the back seat of the family Cherokee. They’ve put tape around some gaps, and while it’s helped a little, it’s still very drafty. Paul mentions the spar carry-through gap between the cabin and the wing. There’s supposed to be a piece of foam in the gap, but often when the wings are removed the foam isn’t replaced. The floor is lifted up, and you can look in the gap with a flashlight and mirror to see if the foam is there. The rear spar also has a gap where there should be rubber discs glued onto the box where the flight controls pass through.

Todd is curious how JPI derives the horsepower number. Mike said JPI keeps the math as a closely held secret. But he said there’s a right way to do it, and it's how Savvy does it. Power is regulated by air or fuel, whichever is in shortest supply. Rich of peak, you have more fuel than the engine can combust, so air is in short supply. Mass airflow is therefore the power determinate, which can be calculated with manifold pressure and rpm. MP is how much air goes into the cylinder, and rpm is how often that happens. Multiplying the two gives the mass airflow number. Power when lean of peak is a function of fuel flow. Fuel flow times a set number based on the compression ratio gives horsepower. He thinks the engine monitor doesn’t know whether it is rich or lean of peak, so it probably computes it both ways, and the lower number is the right one.

Seth has some dry rot on his tires and he’s wondering if that means he needs to change thems. Desser says they need to be replaced when the cord is showing, and his mechanic says the dry rot means it should be changed. The hosts agree with the manufacturer that there’s no minimum tread depth, and to keep going.