John is a maintenance officer in a club, and he is wondering about tire ply ratings. The manual calls for 4 ply, but they often install 6 ply and he?s wondering if that?s ok. The hosts all agree that they have subbed in higher ply ratings when supply dictates. Paul?s rule of thumb is that he always allows a higher ply, but not lower. That?s because the ply rating relates to the weight of the aircraft. Heavier aircraft need higher ply ratings. They get into a discussion on retreads, which can cause issues. They like retreads, but caution that you must ensure they will fit in the wheel well on a retract. Paul worked on a 210 once that caught the skins when retracted.   Doug instructs in Aerostars, and he has worked with a number of clients lately who want him to omit the engine-out portion of the training in order to avoid stress on the engines. There?s talk in the Aerostar community about heavy and light cases. Mike said not to worry about the case. Rather, cylinders that rapidly cool are the concern and that?s because the piston and cylinder are different metal densities and cool at different rates, which can lead to scuffing. They all agree the training is important, but pulling the power back slowly, rather than cutting the fuel, will help reduce the risk of engine damage. Paul makes the point that flight schools do this in Seminoles all day, and that he doesn?t hear of widespread issues. Failure isn?t a concern, Mike said. Scuffing is a wear issue. If it?s an issue, Paul said his pistons probably look terrible, but he?s not going to worry about it. He already borescopes regularly. And Mike said he will run an aux tank dry on a long flight.   Jason has a Comanche 250 with some electrical issues. Throughout the flight the bus voltage will come down. After landing and taxiing in the voltage climbs back up, and rests around 13.8. Recently after takeoff, the low voltage alarm flashed and went to 10.8 while raising the gear. The hosts think it?s a voltage regulator issue, where it works when cold but not warm. Paul said he thinks of voltage as an indicator of whether the system is working and the amps as an indicator of how hard it?s working. It should be around 13.8 or 14 when working properly. Colleen said she had an electrical issue where her JPI would go offline when she would cycle the gear. Under the panel she found that there was a loose connection on the shunt, causing high resistance. Jason?s issue could be at the circuit breakers, voltage bus, voltage regulator, or any number of places. One way to easily troubleshoot is to see if he can find anything hot by running his hands along the wires. Or look for discoloration, Paul said.   Steve writes in asking about oil coolers. During his recent engine overhaul the shop asked if he wanted a congealing or non-congealing oil cooler. Congealing is bad, he thought, so he elected to go with non-congealing. But he lives in Arizona and he?s found the engine runs a bit hotter with a higher oil temperature in long climbs. He?s wondering if he made a mistake. Non-congealing oil coolers have a solid line running through the middle that passes warm oil through the cooler at all times. Mike thinks it?s possible the non-congealing has less cooling capacity because it has less surface area.

Should you trade your aging airplane in anticipation of higher repair costs on your current bird? Mike, Paul, and Colleen have a strong opinion on this. Plus, sticky valves, taking good care of turbos, and engine monitor set-up frustrations. 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: Scott has a Tecnam P2010 with a Lycoming IO-390. He?s had a few instances where cylinders dropped off, the engine ran rough, and then they quickly came back on. It was followed by morning sickness. In essence he had a sticky valve. He found that his CHT temperatures were quite low. At altitude, running the airplane at best cruise power, his CHTs are about 350 degrees. In climb if he leans he can get three cylinders over 350. Mike said he wouldn?t stress about the CHTs, but he would borescope the cylinders to verify that there isn?t too much build-up.   Yuriy has a new-to-him 2010 Cirrus SR22 that?s turbonormalized and he?s looking for some tips on taking care of his turbos. He flies lean of peak at 28 inches. He is limiting turbine inlet temperatures at 1,500 degrees. Mike thinks 1,500 is excessively conservative. The red line is 1,650 degrees, and Mike tries to keep his at or below 1,600 degrees. He also doesn?t subscribe to the one inch per minute reduction of manifold pressure. Lycoming at one time published a document that said not to cool CHT more than 60 degrees a minute. Mike?s engine monitor alarm is at 30 degrees a minute, and he said it doesn?t go off very often. He also doesn?t cool the turbo on the ground before shutting down unless he had high power right before landing for some reason.   Wade has a Cessna 185 with an IO-550. On his last annual he had a few burned exhaust valves. He?s trying to avoid higher maintenance bills in the future. Paul tries to make Wade feel better by telling him that burned valves have nothing to do with how he?s operating the engine and everything to do with the lead in avgas. Going through his operating technique, the only suggestion they have is for Wade to lean much faster, and avoid using the lean find feature. The green arc on his manifold pressure gauge is also wrong. He was worried that he?d have to take off at partial power in order to stay in the green arc on the gauge. The hosts discuss how to reprogram the display.   Matt doesn?t want to throw good money after bad. He?s wondering how long you should hang on to an airplane as it ages. He has a 1977 Cessna T210. Parts are starting to get scarce. It?s hard to find qualified mechanics. He feels like he wants a great airplane that lasts him well into the future. The hosts all agree that it?s better to hold on to the airplane he knows, and not to worry about 210 parts availability, at least when compared to other airplanes. 

Ever wonder how the flap system in a Cessna works? This episode Mike, Paul, and Colleen take a deep dive on the system, plus engine vibrations, leaning for high altitude takeoffs and go arounds, and getting bees out of a restoration. 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: Ken is experiencing vibrations in his Cherokee at certain throttle settings. After installing an engine monitor he discovered that with the throttle at roughly 90 percent full he could induce the vibration, but then quell it by using the mixture. He could see that a cylinder was going offline at full rich, but came back online when leaned. Mike suggests that he needs to lean in the climb to compensate for the overly rich mixture, but Ken said he?s also able to stop the vibration by reducing the throttle setting but keeping the mixture full rich. The hosts still think he?s too rich. They recommend leaning in the climb and keeping the EGT constant as he climbs. Ken also noticed that the cylinder that goes offline is also an outlier on the engine monitor. They tell him to do a GAMI lean test and an induction leak test to try and isolate whether he has a problem or just a poor mixture distribution. Find the test Mike described on Youtube: https://youtu.be/_VfiPuheeGw For more on the induction leak test Paul described: https://www.savvyaviation.com/wp-content/uploads/savvy_pdf/Savvy-Flight-Test-Profile-Expanded.pdf Marcus has a first generation Cirrus and he wants to ensure he is leaning properly for high-altitude takeoffs. Paul said to put his EGT around 1,300 or 1,350 degrees, which will put him close to the Cirrus chart, but is more accurate. For high altitude go arounds, Paul knows his fuel flow at around 1,300 degrees EGT, so he just sets the fuel flow to the expected amount. Luke has been having an issue with the flaps coming down in his 182. What follows is a loooooonnng and detailed description of the Cessna flap system. Blythe was restoring his family?s Cessna 150 and found a bunch of mud daubers. The inspection panels allowed him to clean out some, but he assumes there are more that he couldn?t reach. Paul said the potential corrosion is a key to the solution. He said the bees don?t like to build nests on corrosion inhibitors. He also said to make sure to check up the vertical stabilizer, which is a popular spot. Mike said he?s had luck with moth balls in other machinery. 

Can one high oil pressure reading forever alter your engine? Mike, Paul, and Colleen answer this question, plus the quirks of the O-470, compression test redemption, and repairman certificates. 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: Everett is wondering if his oil pressure is forever altered. He has a Piper Colt with an O-235. The pressure used to be 75 psi, and on a flight the oil temp spiked and the pressured went up to 85 psi. Even after cylinder work, the temperature and pressure have remained high. Paul starts by asking if he?s sure the indications are correct. They suspect a blockage somewhere, although there?s no oil cooler on the O-235. They suggest getting a manual to check for the engine?s entire oil pathway and follow it to see if he can find a blockage. Randall wants to know if the hosts are too hard on compression tests. He asks whether they hold any value. Mike said there?s no harm in doing compression tests, but that one should never change or overhaul a cylinder with compression numbers alone. Knowing where the air is escaping does offer some value, they say. There?s not much you can discover on a compression test that you wouldn?t discover on a borescope inspection that impacts safety of flight, Paul said. Manuel asks how EGT and fuel flow relate on his Cessna 180. He?s seeing a spike in EGTs before they come down again on takeoff. The low compression O-470 will have higher EGTs, especially on takeoff. Mike said Manuel's engine monitor is configured for a carbureted engine, and thus puts a big time delay and smoothing function on the fuel flow. Without the smoothing, the fuel flow would wobble up and down often, making it hard to read. That?s why fuel flow indications rise so slowly after adding takeoff power. And bu slowly adding power, Manuel is delaying the addition of the enrichment function of the carb, which is why he?s seeing a delay for the EGTs coming down. Marty is trying to understand repairman certification limitations. He?s done some work on his prop, magnetos, and so on, and he wants to make sure it?s all been legal. Mike said as he understands it, you basically have unlimited authority to do what you want on your airplane. The common sense rule applies, which is to get a demo or some instruction before you do it for the first time. 

Should you overhaul an engine based on oil analysis? The hosts answer this question, plus fuel pumps, valve grinding, and a pesky hot cylinder. 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: David is worried about the relatively new IO-470 in his Bonanza. His oil analysis history shows a lot of aluminum, and recently, high on all metals. The narrative said to check for crankcase fretting. Paul said he would check the torque on the through bolts for piece of mind. Mike said he?s not particularly concerned about any of the numbers on the report. He said oil analysis is only a trend monitoring system. Once you establish a baseline you look for major diversions from the report. Colleen disagrees and said they aren?t stable, but have been increasing. There?s nothing that would cause all numbers to go up unless there?s dirt or a bad sample. Paul then details how David can use his borescope to look at the cam, a few lobes, lifters, and so on. It might not give him any information, but it could give him some reassurance that things are ok. Colleen suggests inspecting the pick-up screen if he can. Mike said he would never tear down an engine based on an oil report. Maurice wants to know about the fuel pump on his Mooney M20J with a Continental IO-550. He has an altitude compensating fuel pump, and he wants to know how to use it. Mike explains that it automatically leans for you in the climb. Once he?s ready to lean in cruise, it?s time to lean manually. Jared is ready to start grinding some valves. As he gets deeper into lapping valves in place, he?s wondering what sort of threats there are. Is it maintenance to the extent of being subjected to potential maintenance induced failures? Is it better to wait until a valve needs it, or could it be done pre-emptively? Mike said he wouldn?t necessarily do it pre-emptively, but if he sees any sort of potential deposits then it can be worth doing it. Paul said they go through an inspection process afterwards, including making sure the grinding compound is cleaned up as well as possible, that the valve keeper is properly in place, and that the bolts holding the rocker shaft holds are torqued properly. Paul said it?s critical to get another set of eyes and not check yourself. The hosts haven?t heard of any failures from lapping. Chris has an O-540 in his Cherokee 6 that was recently overhauled. His number 6 cylinder spikes up to 450 degrees CHT on takeoff and he can?t figure out why. Mike looked at his data going back before the current engine and found that even the old engine had high temps on number 6. Chris finds that the cylinder also run the leanest. Paul suggests it could be an induction leak. 

A 182 mysteriously losses power and the hosts struggle to explain why. Plus, basic engine temperature theory, confusing ADs, and why it's so hard to find good help these days. 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: Andrey was flying low and slow on autopilot for a mission when he noticed the airspeed dropping. He saw a drop in rpm, and an increase in manifold pressure. He also saw very low oil pressure. He added power, climbed, and returned to the airport. After landing, he checked the oil level and everything was fine. On a run-up check after talking to his mechanic, the engine stumbled. A new oil pressure sensor seemed to have fixed the issue, but he?s wondering if that?s really what was wrong. The hosts agree that it sounds like Andrey was having two issues because a drop in oil pressure shouldn?t impact engine performance. A big drop, or complete loss, will impact the prop governor, but not in the way Andrey experienced. After looking at the data they wonder if there was also something working through the oil pressure relief valve. Willie has a Cessna 310T and is confused about the exhaust AD. He?s getting conflicting information from mechanics and 310 experts. Mike was involved in the fight surrounding this AD, which is so confusing that the FAA had to issue an SAIB after the AD to explain it further. Yet the community is still confused, with the top Twin Cessna shops divided on when the AD should be complied with. Mike said it?s his opinion that it happen at overhaul. Others believe it?s 12 years. Andy is a maintenance manager and wants to know how to teach troubleshooting skills. Paul said in his experience techs can troubleshoot in their heads, do it via manuals and diagrams, or not do it at all. The process should not be, let?s go change this part and see what happens, he said. It should be, let?s go test something and see what we learn from the result. Relatively few mechanics are talented diagnosticians, Mike says. It requires a different skill set. Mike discusses Savvy Aviation?s new mechanic troubleshooting service they are working on. Royce wants to know if power equals risk. For example, if you have a higher compression engine or a turbo engine that produces more heat, will that impact EGT? Are peaks different based on the engine? Mike said CHT is basically measuring how much heat is present during the power stroke, while the EGT is measuring how much energy is being wasted out the back door. Paul said you can see this with an in-flight mag check when EGT goes up and CHT goes down. Running on only one plug shows how it?s more wasteful. Compression ratio is the big determining factor in the level of peak EGT. A higher compression engine will waste less heat, and thus have lower EGTs. 

Can you have a prop strike without a prop? This is one of the more unusual questions the hosts have faced. They also track down a carbon monoxide leak, advise on Continental rpm settings, and help an owner who likely had a pre-ignition event. 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: Robert is an A&P who is trying to help a flight school track down a carbon monoxide leak in a Cherokee. An instructor had a carbon monoxide event, took up a monitor, and found that it was reading at least 300 ppm. The exhaust and heater shroud were replaced, but the cabin was still getting more than 10 ppm. He?s wondering if there is a maximum level allowed in aircraft. Mike said Car 3 didn?t have a maximum, but that Part 23 says 50 ppm is the allowed maximum under current regulations. Hypoxia and carbon monoxide are cumulative, and he said his current comfort is below 20 ppm. He also said leaning impacts CO levels. Peak or lean of peak EGT lowers CO. How it gets in is a bit of a mystery sometimes. He said there was a case where Mooneys with air conditioning were drawing in air from the intake on the side of the airplane. Paul said in a Cherokee it comes in via the forward wing attach point. There is supposed to be insulation to stop it from coming into this area, but over time they are taken out or lost. It?s often not from the engine compartment. It?s through the belly or downstream from the exhaust pipe. John wonders if you can have a prop strike without a prop on the engine. He bought an RV9 with the engine on, but no propeller. He loaded it into the back of a box truck. Stopping partway to check on it, he found the tie-down straps had slipped and the airplane had be banging around in the truck. He?s wondering if he should be concerned, and what he should be checking for. Paul said to put a dial indicator on it and check to make sure it?s less than .005. Some of the bolts on the Van?s prop simulator were lose, and one was hard to screw back in. Paul said he would be surprised if there was any damage. Jesse has a 310 with Continental engines and he?s wondering about the service bulletin that recommends maintaining 2300 RPM in cruise. Previously the hosts said it?s probably good advice when rich of peak, but you could ignore it lean of peak. He wonders if he should go lean of peak first, and then pull the prop back, or is going to a lower rpm first ok? Mike thinks it?s sufficiently brief that it won?t make a difference. Rick had an infant mortality issue with his Mooney. His A&P found valve wear, oil though the rings, and corrosion on the engine, which only had a few hundred hours. He did a top overhaul, flew for 27 hours with the propre break-in procedure. About 30 hours later he got a high CHT indication on a descent, followed by dropping oil pressure. The belly was coated with oil and only 2.5 quarts were left. They found broken rings on 3 of the cylinders. They took off the electronic ignition, but are looking for ideas as to what may have happened. Mike found Rick?s data, which showed the CHT event was in cylinder #1, and the temperature rose at around .7 degrees per second. That approaches Savvy?s rule of thumb that anything at a rate of a degree per second or higher is a pre-ignition event. The hosts think it's possible the electronic ignition was the culprit. He thinks the broken rings may be an unrelated event. Colleen said improper ring installation could have caused the new ones to break She also suggests checking to make sure he doesn?t have a cracked plug. 

How to identify CamGuard in an oil analysis, erratic idles, how to check the oil, and what the wrong prop does to an engine are on tap for the latest episode. 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: Tan has a 1968 Piper Arrow 180. He has an erratic idle as the engine warms. Mike and Paul said it sounds like maybe sticky valves. He and his mechanic haven?t done the wobble test. It almost can?t be a spark plug, Mike said. Colleen said it could be an ignition harness. Paul suggest he could do an in-flight mag check to help verify. Even though it should start with morning sickness, Paul said it?s not unlikely that it?s a sticky valve. Fuel could also be an issue, as they?ve cleaned the injectors, which Mike, Paul, and Colleen think they induces more problems than it solves. Dicky is concerned about his last oil analysis report. Some of his wear metals are much higher since he?s been using CamGuard, and he?s wondering whether that?s normal. High calcium and high phosphorus are CamGuard?s signatures on an oil analysis, according to Mike. One thing Mike noticed that Dicky didn?t ask about was high silica, indicating dirt in the engine. High silica usually brings high wear metals because the dirt acts to scrub the cylinders. Dicky said he had a problem with his air filter box, and had replaced a part. Enock is trying to settle a flight school debate. He checked the oil and the instructor asked if he screwed the dipstick back in when checking it, or if he just tapped the stick to the top of the tube. Everyone he asked at the school had a different answer. Paul said he screws it back in to check. Colleen agrees. Mike said all the readings should be taken with a grain of salt. He recommends running about two-thirds full. Many type certificate data sheets have a minimum level. And the only somewhat accurate reading is the first one of the day when the oil has time to fully drain back into the sump. Rex is doing his best to follow the hosts? leaning guidance. He has an RV-8 with an IO-360 engine with high compression pistons and e-mags and a fixed pitch propeller. He isn?t able to lean full throttle, but he can at cruise power. Mike clarifies that the guidance to leave the throttle full forward was for constant-speed propellers. Operating lean of peak slows the combustion event. The flame front takes longer to propagate. Engines don?t like lean of peak if the rpm is too high because the faster speed of the engine doesn?t like the disparity. Mike said he lowers rpm while keeping the throttle full before he leans. Then Rex makes an off-handed comment about his prop pitch, which the hosts quickly pick up on. They are convinced he has the wrong prop. He?s only getting 2400 rpm at full power in cruise. He also had a denotation event, and is trying to determine what the normal timing is supposed to be.

Clogged injectors, how to care for an engine while training, avoiding costly altimeter checks, and engine design considerations are on tap for this episode. Email podcasts@aopa.org for a chance to be on the show. Join AOPA to become a member of the world's largest aviation community at aopa.org/join Full notes below: Marko?s engine had a strong revving sound on takeoff. He saw that he had an EGT above 1,800 degrees and one that was below baseline. A run-up after landing made it seem like it one cylinder wasn?t firing. A borescope inspection revealed nothing unusual. A subsequent check of the injectors found that there was debris in one. His mechanic suggested it was a blocked injector. He?s wondering what would cause that. It turns out this event was soon after the annual when the injectors were cleaned. The hosts agree that the maintenance is clearly what caused the clogged injector. Mike said this is such a delicate operation that he thinks it?s almost as if the fuel system should only be cleaned under sterile conditions. Colleen said she used to clean hers, but now doesn?t because she knows the risks. Paul colorfully describes the problem of cross-contamination. Dylan teaches in a carbureted Seminole and he wants to treat the engines well, and is looking for best practices. He mentions shock cooling, which the hosts quickly debunk. The school?s engines are over TBO and they?ve never had to replace a cylinder. Obviously whatever the school is doing is working. He?s also wondering about failing the engines. Lycoming recommends failing the engine with mixture, but many people like to shut off the fuel. Mike said he wouldn?t worry about shutting the engine down from the fuel selector, and that it shouldn?t introduce air or other issues. Mike worked in the auto industry for many years, and he works on his own airplanes as much as possible. He?s wondering why aircraft engines don?t have ventilated crankcases. Mike said crankcase ventilation is primarily for environmental reasons. And piston aircraft engines have significantly more blowby. You don?t want to keep it in the crankcase. He said air/oil separators return a lot of junk back with the oil. You want the filth to leave as much as possible. Doug has three altimeters in his airplane, and he?s wondering how to save money on the checks. Mike thinks he shouldn?t be charged three times for three checks because you hook up the equipment once, and adding on a second or third altimeter doesn?t take too much additional time. Each check includes about five tests, according to Paul, and each has to be separately documented. 

Mike, Paul, and Colleen sludge through oil pumps that lose prime, skipping an oil filter change, and using the right oil in this Texas tea-themed episode. 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: Mike has a Cessna Bird Dog with an oil pump that isn?t cooperating. When he lets the airplane sit for a month or more, he doesn?t have oil pressure on the first start up. He?s conceived a workaround of pumping oil by hand into the engine and turning the prop backwards. Paul and Mike both describe having experienced this issue with Continentals. Mike said that Continental told him to prime the pump by removing the top spark plugs and pressurizing the case with shop air while you move the starter. Paul said they will unscrew the oil filter, fill it with oil, and then put it back on. Cameron is trying to protect the Aeronca that?s been in his family for decades. He thinks using thinner oil sounds good because its viscosity helps after not starting for a long time, but the thicker W100 might better protect? He flies mostly in the winter, but he preheats. Mike thinks his strategy to use W100 when it?s warm and multiweight is good for colder temps. Paul likes multiviscocity so he doesn?t have to worry about temperatures. Chuck is an A&P with another job, and he?s considering maintenance side hustles. He?s thinking of offering aircraft weighing services. He can either defuel aircraft or completely fill the tanks prior to going on the scales. Advisory circular 43-13 is unclear about which approach is better. Paul has always thought it strange that proper weighing procedures are in the POH, and not the service manual. That?s the first place to check, and the procedure that should be followed first. If there?s no procedure you go to the AC. He finds that most airplanes must be de-fueled first. Mike says to use FAR 43.13(a), which says that the mechanic must use the procedures in the maintenance manual, or acceptable practices and techniques. The AC has a note at the beginning saying that it?s only to be used if the manufacturer doesn?t have a process. But given that the procedure is in the POH, and not the maintenance manual, Mike suggests Chuck can pick and choose the way he weighs the airplane. Jared is looking for a more permanent oil filter solution. First he wonders if he can skip changing the filter when changing the oil, in part because they were hard to get at one point. Paul said the only time it?s required to change the filter is during annual, when the IA is required to inspect it. Mike said he would like to inspect the filter as often as possible. He considers it the most important thing to do to monitor engine condition. Although people have taken their filters beyond 100 hours, there is oil analysis data showing that it?s a bad idea. The hosts then discuss reusable oil filters. Mike changed to reusable filters prior to Oshkosh, and has been initially pleased with the results. The Challenger filter comes off, the filter element comes out of the can, and the filter then washed. He was astonished by what came out of the filter because it?s easier to see what comes out after washing versus having to see what?s in the pleats of a filter.

Lean of peak is causing odd vibrations in a Commander, and the hosts discuss proper troubleshooting. Plus carb heat on the ground, dehydrators, and parts no longer manufactured. Email podcasts@aopa.org for a chance to get on the show. Full notes below. Chip said his mechanic is concerned about lean of peak because we don?t know the actual temperature at the valve, as the temperature is taken downstream. Colleen makes the point that EGT temperatures are fine because it?s well below the valve limit temperature. Mike said valves burn only when they don?t seat properly. They shed their heat through physical contact with the seat at the cylinder head. They also shed it through the valve stem. Detonation once flying lean of peak isn?t a concern. It?s getting to that point that?s the biggest risk. Paul suggests that once you know the fuel flow at your desired power setting you can lean straight to that fuel flow and not worry about EGT or CHT until it?s set and stable. Chip is also concerned about a vibration in the floor of his Rockwell Commander. Mike suggests he do some testing to help isolate the issue. If it goes away at certain rpms, then it suggests that it?s an engine-based issue. At a constant rpm but with changing pitch, it suggests a potential airflow or airframe source. Frank is questioning the logic of the Luscombe handbook. It says to put the carb heat on for takeoff. It?s also placarded that way on the panel. The hosts can?t figure out why this would be required. The hosts suggest he ignore the handbook and operate as he would in other airplanes, in part because the engine would be breathing unfiltered air while on the ground. Bill has a Cessna 180 on floats with an O-470-50 engine. For the last few months he hasn?t been flying as much and he wants to preserve the longevity of the engine. He is looking for details on engine dehydrators and whether they actually work. Colleen looked through some research and found that those who had done some side-by-side testing had found good results. Mike said Tanis found that people who ran their heaters all the time were causing corrosion, but that if they use engine dehydrators they are fine to run the heater all the time. In other words, they seem to work. Mark is pushing back on airport naysayers that tell him autofuel is dangerous. He flies airplanes with older, small Continentals, and with all the info that has come out on the transition away from 100LL, he?s wondering if he should be worried. Mike said running on autofuel is the best thing he can do for his engine. People tell Mark he has to run at least half low lead. Mike said they?ve never seen issues with low compression engines running on autofuel. Mark flies from an airport a mile high, and locals are also telling him that vapor lock is also an issue. 

Rough idle, electronic ignition basics, airplanes to avoid (or not), and the difference between detonation and pre-ignition are on tap for this episode. Email us at 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: Stephen wants to get the engine on his Cessna 206 purring. At idle the engine stumbles down to 600 rpm. It never quits, but doesn?t run smoothly either. Mike asks if they?ve done an rpm rise test at 600 rpm. Paul explains it?s part of the installation process of a new engine. You set the engine at a set rpm, then pull the mixture back slowly to get a 25 rpm rise. More than 25 rpm means it?s running rich. Less than 25 rpm means it?s running lean. Engines don?t come out of a crate ready to go. They need to be set up properly. Mike also said that landing with full mixture rich is an issue as well. He said there are only two times you should have full mixture. One is when starting cold, and the other is when applying 100 percent power (at lower density altitudes). Mark is interested in electronic ignition for his 210, particularly the Surefly. Paul loves the Surefly on his airplane. He doesn?t love the advanced variable timing. He thinks a bit aggressive. But it is selectable, so you can turn it off if you like. Mike said he would try it with the variable timing on, and only turn it off if the CHTs are too high. Colleen said her husband has done the dual Surefly on his Legacy. He has higher CHTs, but not unacceptably high. The fuel burn is also lower, but the biggest benefit is easier starting. Erick is looking for any angle to justify buying his first love, a Cessna 337. He would prefer a turbocharged Skymaster. He?s wondering if there?s any hope for the future of these engines being affordable. You must go and buy a turbocharged Skymaster, Mike said. The engines that Mike has previously been worried about are on the pressurized Skymaster. The turbocharged engines are rated at 210 horsepower, and the pressurized ones are rated at 225 horsepower, which he thinks impacts longevity. He thinks engine longevity is related to horsepower per cubic inch. An O-470 is about .5 horsepower pre cubic inch. The TSIO-360 is around .625 horsepower per cubic inch. Warren is wondering if detonation caused a power failure in an accident he?s studied. The NTSB data shows that the cylinder reached about 700 degrees, and it went up by about 1.3 F degrees per second. Mike said CHT increases greater than 1 degree per second can only be caused by a pre-ignition event. It means that something in the cylinder was either acting like a glow plug, or if there?s a magneto failure. A cracked spark plug insulator can act like a glow plug, for example.

How do you know when to replace certain parts? They begin to talk to you. Find out what, why, how, and when when Mike, Paul, and Colleen tackle this and other questions. 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: John is part of a club that owns a Cessna 172. Another member told him he shouldn?t move the rudder by hand when he preflights. Mike said to make sure he pushes it at a rivet line to ensure he doesn?t bend the sheet metal, but otherwise it?s ok. Paul describes how the system is built. He said in a Skyhawk the rudder pedal tension is created by springs that pull them toward the firewall. There?s not a cable tension spec. The steering bungees are between the rudder pedals and the nose gear. If you get in and push the pedals when stationary, you are putting stress on the bungees. Jarek wants to know if the FAA has lost its mind. He is wondering about the FAA?s AC 20-105, which says that engines that run past TBO have a higher rate of failure, and that engine overhauls at TBO are usually cheaper than those that are run beyond. Mike said Lycoming had previously issued a white paper that said that the typical lifespan of a crankshaft was 14,000 hours. Camshafts have corrosion issues, and don?t cause failures, and sometimes gears need to be replaced. But rarely does time impact safety. There are people inside the FAA who disagree with the policy, Mike says. On one hand they require manufacturers to set a TBO. On the other hand, they tell Part 91 operators that they can ignore it. Typically engines that fail that have run beyond TBO tend to be not related to age, but because of maintenance resulting from the fact that the engine is older. In fact, it?s usually the opposite, Mike says. Lower time engines typically fail because of infant mortality. Aaron and a partner recently purchased a Seneca with turbo Continental TSIO-360-KBs. They installed new intercoolers and the manual revision suggests new power settings. He?s ignored the chart and is flying around 30 inches lean of peak. Mike said the chart is interesting if you are operating rich of peak, but irrelevant lean of peak. The power output of the engine is determined by whichever component is in shortest supply. Rich of peak, you have more fuel than you need, so power is controlled by air through the throttle and the prop. Lean of peak, fuel is in shortest supply, so power is controlled through the mixture. He would run a slightly reduced throttle, just to avoid overworking the turbos. Rory has a Cardinal that he bought 12 years ago, and he hadn?t ever changed the ignition wires. So he started to wonder about when and why to change them. The hosts agree that if a wire fails it feels like a stumble or mis-fire because it just takes one spark plug offline. They say to run them on condition, and only change them when they start talking to you through mis-firing.

Metal in the filter, starting problems, and mechanics who don't understand the definition of installed are on tap this episode. 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: Roger has a Mooney M20J that has developed an odd starting problem. Over the past few years he?s had to increase the time the boost pump runs before the engine will start, and even then it sometimes doesn?t fully catch. Paul suggested that the bellows inside the flow divider could be bad, which would cause it to perform poorly. Mike also suggested that the idle mixture could be set incorrectly as well. An rpm rise test can verify if it?s correct. Craig has a 182 that he uses to go back and forth to his fishing cabin. He took the back seat out and he wants to add in some plywood in the back to protect the structure. He isn?t planning to affix it in any way other than Velcro. His A&P told him to avoid doing this because the wood isn't burn certified. But without installing the plywood with a structural fastener, it?s not technically installed and he can carry it however he likes. Malcolm has an 182 with the Texas Skyways conversion, and it hangs up during the starting sequence. They?ve replaced the starter, bought a battery tender to check the battery, and more. It?s so obvious what the problem is, Mike says. This is a classic and common problem among Continentals. The starter drive adapter is bad, the hosts say. He can have the part repaired and it should no longer be a problem. Aaron found a significant amount of metal in the oil filter on his Piper Cherokee 140. There was aluminum in every pleat of his filter after only about 15 hours. They were thin, but large flakes. The pieces were too big to even show up in an analysis. No other metals were elevated in the analysis. Colleen suggests that it could be from the oil pump impeller, but since he only found oil in the filter, and not in the sump itself, he thinks it?s coming from the pistons. Mike said piston pins migrate back the other direction, which often means it?s self-resolving. As it turns out Aaron knew the answer. He removed all four cydlinders, and two of the piston pins were severely worn. They also found ring chatter. Mike said Superior has had issues with ring chatter and they?ve tracked down the manufacturing problem and replacing the cylinders under warranty. 

An airplane that hasn't flown in 8 years quits when going to full power. A turbocharged Mooney meters out less fuel as it climbs. Mike, Paul, and Colleen tackle these questions and many more in 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 Eric is having trouble with his Aero Commander. The engine has only 150 hours but sat for 8 years. After an extensive annual, they test flew it. One of the engines dies at full power, but runs fine at partial power. The flow dividers were checked, the fuel lines were blown out, and the fuel servos were bench tested. Colleen suggests that it could be a blockage of the exhaust, especially given the long sitting time. Paul thinks it?s possible that a lack of air supply could be a problem. They suggest opening the alternate air to see if that fixes it. Paul said he would go through the entire induction system to verify it?s clear and open. Will is struggling to get the fuel system set up in his turbo Mooney. As he climbs he says the fuel pump is decreasing fuel pressure. The manifold pressure starts to decrease when fuel pressure gets low in the upper teens. Mike said there?s nothing wrong with the manifold pressure or upper deck pressure. The line from the upper deck pressure to the fuel pump aneroid is bad. The aneroid thinks it?s seeing lower pressure as he climbs, even though it shouldn?t. He thinks there?s a leak in that line, the aneroid, or the upper deck pressure. He suggests pulling the b-nuts and replacing the seals first. Jim is wondering about how to lean when flying low in a formation fly-over. With 10 airplanes and lots of throttle changes back and forth, it?s hard to know how to lean. Colleen suggests doing some tests at the same altitudes not in formation to see what sort of power settings he?s at and apply it based on those tests. Mike said he would lean to around best power. Jason is a partner in a 182 and a potential new partner went for a test flight and found a potential issue. The rpm dropped 150 to 170 during the mag check, and he refused to fly the airplane. So he?s wondering if the pilot was overreacting or if he was right not to fly it. Paul said EGT rise is a better indicator than rpm drop. Very little drop or no drop could mean the P leads weren?t connected. Mike said bigger drops, like 300 rpm, should prompt a timing check. Switching to one plug has the effect of artificially retarding the mag timing. If it?s already retarded, that can make a large drop

Live from Airventure 2024, we present the first of two sessions. Listen as the audience tries to stump Mike, Paul, and Colleen with its toughest maintenance questions. Email podcasts@aopa.org for a chance to be on the show. Join the world's largest aviation community at aopa.org/join

An owner wants his engine perfect for flying around the world, how to start an airplane with electronic ignition, when to fire your mechanic, and defining approved data are on tap for this episode. Submit your questions to podcasts@aopa.org for a chance to be on the show. Join the world's largest aviation community at aopa.org/join Full show notes below: Ethan is flying a 182 around the world, and he is worried about a CHT imbalance. He?s added an electronic ignition, changed some baffling, changed cylinders, and even got a new engine. It also gets worse as he levels off. Paul said Ethan still has a baffling issue, and the first step is to cut slits in the material to make sure it?s laying flat. The temperature imbalance changing when leveling off makes sense to Paul because the airflow over the engine changes as the pitch of the airplane changes. Mike said it can be inter-cylinder baffling as well. Even CHTs are impossible, he says. A 50-degree spread is good. Colleen suggests pushing the baffling off the back cylinder by wedging in a spacer between the cylinder and the baffling to create a small gap. Frank just installed an electronic ignition for his 182 and is wondering how to properly start the airplane with a split switch. He has been starting it on battery only, as per the airplane handbook. Paul made the point that older Cessnas didn?t have a split switch. Theoretically with the alternator on during the start, you avoid an electrical jolt, although he said he can?t say the battery only start is always better. He recommends starting on both mags. Mike said the only time you wouldn?t want to turn the alternator on during a start is if you have an almost dead battery. It?s more important to avoid the jolt on a gear-driven alternator. Benny is headed for a bread-up with his mechanic. He likes the work the mechanic has done, but in talking to the mechanic about his approach to maintenance, he is concerned they don?t agree on tactics. The mechanic doesn?t believe in lapping valves, for example, and may have a hard adherence to TBO. Benny wants to know whether to switch now or try to work through the disagreements. Mike thinks it?s worth a conversation given how difficult it can be to switch mechanics. Colleen said it?s not going to work, and that the mechanic is most likely set in his ways. Paul agrees that getting a mechanic to change his mind is incredibly difficult.  Dwayne is restoring an antique airplane is wondering what constitutes approved data. Xerox copies are acceptable, despite what others have told him. He also wants to know if reverse engineering a part is considered approved data. Dwayne and the hosts discuss the difference between acceptable and approved data. 

An owner wants to know if he should tear down his engine after harvesting some corn with his prop. Plus, the benefits of flying oversquare, why you should use the boost pump at higher altitudes, and pre-flight procedures. Send your questions to 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: John wants to know if he can manipulate the rudder on his club?s 172 during a preflight. Another club member told him he would stress the nosewheel steering by doing that, but the hosts agree that John that was right. Paul explains that the tension on the rudder pedals is created by springs that pull the pedals to the firewall. The steering bungees are between the rudder pedals and the nosegear, not the rudder. The rudder may move the pedals a little. Bigger stress is when you move the pedals from the cockpit without the nosewheel moving, but even so, Paul said the system is made to do that and is unhurt by those checks. Jeff had a botched landing in his Super Cruiser and hit some corn at full power, and he is wondering whether or not he had a prop strike. The engine didn?t seem to have an rpm drop, and the prop was undamaged. Mike said there?s two possible outcomes. The first is that he didn?t have a prop strike because there wasn?t a reduction in rpm. If Jeff thinks he had an rpm reduction, the AD requires the accessory case to be removed, but not torn down. In all the prop strike events Paul has been involved with, he?s never seen rotational damage due to a prop strike. Magnetos are usually the first thing to be damaged. He said he thinks it?s also unlikely there wasn?t an rpm reduction as it slashed through the corn, and he thinks Jeff is subject to the AD. Tyler is looking at buying a turbo Piper Arrow and he has questions about turbocharging. He wonders about the diminishing returns of oversquare or overboost as it relates to reduced longevity. He?s also worried about boot strapping, which Paul said is self-limiting. Mike said the highest amount of oversquare allowable within the operating envelope is the most efficient place to operate. It?s important to remember that the chart is rich of peak, and lean of peak provides more of a detonation margin. Mike said the abuse to worry about is horsepower per cubic inch. Fred?s engine on his Cirrus had a hiccup and he?s wondering why. He was at 10,000 feet climbing in the clouds. One cylinder was getting hotter, and one had passed 400, so he leveled off, things cooled off, and he started climbing again. Just as he leveled off he tried to do the big mixture pull, it stumbled, so he pushed it forward and it still stumbled. The hosts quickly figure out he had vapor lock. Paul said a lot of Cirrus pilots run the boost pump on low all the time. Mike does that on his 310. With a hot engine and high altitude, the fuel is vaporized, so the boost pump helps move things along a bit. 

Lots of leaks this episode, as Mike, Paul, and Colleen diagnose a leaky strut, a defroster that's not working, a leaking brake system, and more. Send 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: Greg has a Cherokee with a leaky strut. His mechanic suggested pressurizing it with shop air instead of nitrogen. He asks about Granville Strut Seal. Mike said he has a big success rate with Granville, and that he should definitely use it on all the struts. He disagrees with Greg?s mechanic that shop air is ok to use to fill a strut. The reason to use nitrogen is to avoid corrosion inside the strut because shop air has moisture in it. The air valve in the top of the strut is probably where his air is leaking from. Jim has a Mooney M20C and the defroster ducting is falling apart. He?s wondering how to replace it. They recommend taking out the glareshieild, grabbing out the tubing, and buying a new one from Lasar or the factory. The existing one might be repairable with epoxy or new fiberglass pieces. Paul cautions that it?s possible something won?t work after he gets it all back together. Mike thinks it?s almost not worth fixing because of the complications in that tight of a space. Andy is trying to understand the carb ice potential of the Cessna with an O-300 that he?s flying. He?s heard it?s very prone to icing, and the carb temperature gauge shows it?s almost always in the yellow. To stay out of the yellow he would need to fly with the carb heat on almost all the time. Mike said the extreme dryness in a Minnesota winter would make carb ice unlikely. Nick has a few questions about his 182. He?s first wondering when to replace the battery. Mike said that the way to check is an annual capacity check, and there?s an official and unofficial way to do it. The official way is to buy a capacity checking instrument, but that?s expensive. First fully charge the battery, then time how long it takes to go down to a certain level. If it gets below a certain ampere-hour rating, it?s time to replace it. Unofficially you can draw current in the airplane and see how long it takes to draw down. But the act of the capacity check seems hard on the battery, according to Mike. Paul said Concorde has told him it?s not an issue, and that checking them doesn?t damage anything. Nick's second question deals with the brakes. When he bought the airplane he saw in the logbooks that they were being rebuilt once a year. He changed out the master cylinder, the flexible line, the o-rings, and he blew out the line. It?s better, but he still has to occasionally fill the reservoir. Paul suggests checking the line near the calipers. If it?s a solid tube, he said it?s possible that fluid can work it?s way back up the system. He suggests leaving a rag wrapped around the top of the reservoir and fly to check if that?s where the fluid is coming from.

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. Join the world's largest aviation community at aopa.org/join 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. Join the world's largest aviation community at aopa.org/join 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. Join the world's largest aviation community at aopa.org/join 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. Join the world's largest aviation community at aopa.org/join 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. Join the world's largest aviation community at aopa.org/join 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. Join the world's largest aviation community at aopa.org/join 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.

A Vans customer wonders what to do next, and a 172 pilot asks if carb heat is really necessary all the way to the ground. Plus, the best spark plugs, and a vexing gear issue are on tap for Mike, Paul, and Collen this time. Email podcasts@aopa.org to be on the show. Join the world's largest aviation community at aopa.org/join Full notes below: Greg has a kit from Vans on order and he?s wondering what to do next. He can replace his quick build wing kit with the small cracks installed, but he wants to know if he should order replacements. Paul said when sheet metal work is done on certified aircraft in the field, a lot of cracks naturally come up. Greg said a customer has to agree to accept the modified terms of the new contract, and you have to either accept what they send you, or spend money on a second kit. Paul said to deburr as little as possible. The goal is clean, sharp corners, not a knife edge that can cut the rivet. Just barely touch the hole, he said. Travis has an unusual gear problem. He was tasked with ferrying a Wheeler Express RG, an unusual experimental. On the ground the gear works perfectly, but when flying it won?t reliably retract. The system is based on a Glasair 3, and Colleen said the Glasair racers have a similar experience with their airplanes at Reno. On a ferry flight the hydraulic fluid built pressure over a few hours, and Travis had to select the gear down lever in order to release the pressure. Paul said not to spend any more time on the system, and replace it with something from Cessna. Brian wants to get to the bottom of the fine wire and massive plug choice. His shop said he had to replace all 12 fine wire plugs at the last annual, all with around 800 hours on them. The shop recommended Temptest massives, which is what he did. He?s wondering if there?s really a difference in performance. Paul said fine wires tend to idle a little better and smoother. Corrosion was an issue on older Champion fine wires, which is what Brian had. And the ceramic is thicker on Tempest. Fine wires also last longer, usually long enough to cover the additional cost. Mike said they cost about four times as much, but last four times as long. He said some people also report smoother operation at very lean mixtures and small fuel economy improvements. Colleen has fine wire Tempests in her Cardinal but massives in her Skybolt. Her fine wires run a bit cleaner and don?t need to be gapped. Brian has seen a larger EGT differential when flying lean of peak with the massives. Dennis has a 172 and he wants to know if it?s really necessary to keep carb heat on all the way to the ground. Mike said a newer Lycoming Skyhawk is less susceptible to carb ice, but his Continental O-300 is much more likely to produce ice. He recommends installing a carb heat gauge if he really wants to avoid having the carb heat on longer than necessary.

This episode Mike, Paul, and Colleen help an owner with an engine that randomly dies after 2100 rpm. Plus, the role of avgas as a lubricant, prop governor issues, and getting back into maintenance. Email your question to 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: Dennis has a Cardinal RG with a prop governor issue. When it?s warm, the prop underspeeds just a little. He?s done a bunch of troubleshooting, and he is at a loss. The manufacturer said to send his prop in, but he is reluctant to do that given how often prop shops deem them unfit for continued service. Dennis is an A&P and he asks if he is allowed to open up the governor and work on it. Mike said he doesn?t advise it because he both can?t do it legally and doesn?t have the right tools. Both Paul and Colleen said their props do the same thing, and they recommend he crank up the rpm just a little since a small amount of overspeed is allowed under the type design. Luis is looking to get back into aviation maintenance after earning an A&P many years ago. The hosts debate the FAR, which says that a mechanic is current if the Administrator deems he or she so, or if the mechanic has served as a technician for the past six months. The hosts think Luis should use the preventative maintenance provisions to do the work without supervision. Jeff built an airplane with a PZL Franklin 235 and the engine won?t make full power. The static rpm is 2800, and anything beyond 2100 kills the engine. He thinks either his homemade exhaust is causing too much back pressure, or there was a manufacturing issue. He wonders if there?s a way to isolate the problem. The ignition timing is set to 32 degrees, which is the manufacturer spec. Mike and Paul recommend backing off the timing first to see what happens. Paul suggests he could also remove part of the exhaust to see what happens. Josh wonders if we are too eager to get off avgas, specifically because of its proprieties as a lubricant. He?s always heard that it lubricates valves, but Mike thinks it?s probably not a concern. It?s true that before valve seats were hardened, there was some microwelding, which led to valve seat recession. Lycoming switched to hardened valve seats in the 90s, and Continental switched in the early 2000s. There is a possibility that some of the older Continental cylinders could have problems with valve recession, but it's too early to tell. He details the work that AOPA is doing with the dual-fuel Baron, which is seeking to understand some of these issues.

Mike, Paul, and Colleen help an owner raise his oil temperatures, explain the rules around ELT battery replacements, debate the merits of a tuned exhaust, and help an owner whose airplane won't quit. Email podcasts@aopa.org for your chance to get on the show. Join the world's largest aviation community at www.aopa.org/join Full notes below: Chris has a Super Decathlon with CHTs as low as 270 degrees and oil temperature around 150. Even with the oil cooler covered during winter, it still doesn?t get hot enough. Mike said they like to see oil temperature up to 200 degrees if possible. Chris can check the vernitherm by putting it in boiling water to see when it actuates. Mike said the oil temperature gauge is typically reading at the coolest part of the process, and the oil may climb 40 degrees higher. Curtis just wanted to change his ELT battery. His mechanic sent it away to a service center. He received an invoice with three options, none of which included replacing the battery. His standby current apparently tested high. Unfortunately Curtis was in an unusual situation with a foreign-produced part. There are two answers, Mike said. There?s the answer where you feel like you have to follow the manual, and one if you follow the regulations. The manual says the battery must be replaced by a Part 145 shop, but the regs allow the owner to do it under preventative maintenance. Mike contends that since the battery replacement section of the manual is not an airworthiness limitation, Curtis can just brush it off. Pierre-Louis and his club in Switzerland have a tuned exhaust system on their airplane and while he is seeing some benefits in terms of fuel burn and climb rate, he is most interested in the smoothness of the engine. He said it feels like having a 6-cylinder engine and he?s wondering if tuned exhaust systems offer better engine longevity. Colleen thinks it?s possible the engine is actually working harder (more horsepower), so she guesses that the engine longevity would be reduced. Mike said he disagrees because the engine isn't producing more power, its power is being used more efficiently. Paul suggests that less vibration is ultimately better for the engine. Frank has a Rockwell Commander 112 and when he shuts it down it sometimes diesels, or won?t entirely quit. Typically it only happens in the summer after a flight when it?s warm. Mike and Paul said the only way that happens is if the mixture doesn?t fully shut off the fuel supply. Mike said the mixture cable to the carb is the first place to check. Colleen suggests that it could be a leaking primer as well. Mike recommends fault isolating it by disconnecting the primer to see if it resolves. 

This episode Mike, Paul, and Colleen debunk myths, describe valves that are eligible for lapping, and cover the basics of the red box and leaning. 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: Maciej is a new private pilot who is questioning some operational procedures he was taught. He was taught not to put fuel back into the tanks after sumping it, and he thinks if you sample it and it?s clean, why not put it back? The hosts agree that if the sample is clean, put it back. He also wonders about oversquare on the impact on the propeller. A ground school he took says that it is too hard on the propeller to run it at low rpm and high power. Mike questions the validity of this, and Paul said to go ask the source because it doesn't seem right to him either. George has an airplane with some valve issues. Five of his cylinders have varying levels of green on them. He was told that four could probably be lapped, but the fifth has to be pulled. He?s wondering if green on a valve, which is later lapped clean, weakens or otherwise compromises the valve. Most of the green you see is green deposits, according to Mike. In early days of borescoping cylinders, the colors on the face of the valve were all we had to go on. Now, when we can position the camera between the valve and the seat, and can see if there?s erosion. If there isn?t erosion, it?s a good candidate for lapping. Mike said as long as the valve isn?t a train wreck that it?s worth lapping. Most people don?t do it aggressively enough. Doug is an instructor who was flying a Cessna 182 with a client and the owner didn?t want him to lean, even though they were flying higher than 8,000 feet. Finally he convinced the owner that it was ok to lean a little to smooth out the engine. Apparently the owner was worried about the red box. Since the goal is to stay below 400 degrees on the cylinder head temperatures, Mike thinks it?s hard to get 182 cylinders that hot at altitude, and below 400 degrees there is no red box. Paul makes the point that because power output at 8,000 feet is below 65 percent, you can?t hurt the engine by leaning.

With everything going electronic in the cockpit, will owner-produced parts become a thing of the past? Plus, Mike, Paul, and Colleen talk about their least favorite magnetos, deferring maintenance, and more. Email podcasts@aopa.org for a chance to be on the show. Join the world's largest community of aviators at aopa.org/join Full notes below: Justin owns a Columbia 400 and he?s wondering if he can make owners-produced parts for some of his electronics. The hosts agree that this is a problem with aircraft maintenance. Because it?s difficult to show original design criteria for electronics, it?s hard to prove the part meets the original standards. There are a lot of things you can?t easily duplicate, Paul says. Ben is a new aircraft owner and a lot of the previous squawks were deferred. He wants to know what he can do to help keep the airplane in top form before the next annual. Most of what Ben mentions is preventative maintenance and relatively minor. Paul said to focus on corrosion issues, including at the forward and aft wing attachments. Those are steel attached to aluminum. If you catch it early you can avoid future maintenance issues. Paul recommends using FAR Part 43 Appendix D as a guide for the what Ben should watch for. Colleen said to focus on things that would be expensive later. There?s a lubrication chart in the service manual, and Paul said to use that and go over the entire airplane. David had a scary experience in his Lance. He was approaching an airport and lost power. He ran through a checklist and nothing helped. At about 400 or 500 feet, descending toward a beach, he got a stall warning. The stall warning caused him to pitch forward abruptly, and the engine restarted. He was able to come in and land normally. After some extensive testing they found that a spring had broken in a mag. David thinks that maybe the spring was wedged in the wall of the case, and dislodged when he pitched forward. The hosts don't see how that's possible, but without further information, can't make a better diagnosis. Ray has a P210 and used an in-flight mag check to diagnose a problem. He was flying back to the States from Canada and he noticed the engine was running a bit rough. He checked the mags and found one wasn?t operating properly. He later decided to stay on one magneto. He?s gone through three magnetos in the past few years. He wonders if continuing the flight on one mag was a good idea, and what he should do now. They all agree that he did exactly the right thing by continuing and flying on one mag. Mike said he hates pressurized magnetos, and he would swap them out for electronic mags ASAP. 

Why you shouldn't jam the throttle forward launches this episode. Also, Mike, Paul, and Colleen help an owner with high oil temperature, advise a builder on engine modifications, help ease the mind of an owner with water in his tanks, and discuss how best to use a borescope. 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: Juan has a turbocharged 210 and he's having trouble going full power on takeoff. He flies out of a high elevation in Colorado, and when he rapidly goes full throttle the engine will quit. It's a bad idea to jam the throttle forward quickly, Mike said. That's especially true with turbocharged engines. Mike said he throttles slowly enough that he's about at full power at rotation speed. Paul points out that even if your oil is at 130 degrees on the gauge, that's not the temperature in the entire system. Everywhere outside in the hoses, etc, is colder. Advancing the throttle quickly can choke the system. Also, in the turbo 210, you can't just slam things forward. You must modulate the manifold pressure because overboosting can flood the engine.  Andrew has a 310 with high cylinder head temps and oil temps on his right side. Some new plugs and new baffling has helped his CHTs come into control. His oil temp is still high. He's replaced the vernitherm, sent out the oil cooler for overhaul, and done some other troubleshooting. The hosts suspect airflow because it happens under reduced power on descent. There's a baffle that separates the cylinder and oil cooler that Mike thinks could be an issue. Paul suggests flying with a GoPro or a borescope camera in the cowling to see what happens in flight.  Dan is building an RV10 with an IO-540 that he's going to overhaul before he installs it in the airplane. He's considering going to 10:1 pistons and porting and polishing and he's wondering about performance and reliability. Mike throws a little cold water on Dan's plans. He thinks it's not worth the risk. Colleen made a pro/con list and she said they are forged, which makes them stronger. They are more energy efficient, but that means they burn more fuel. There's a different magneto timing. They run at a higher pressure, and that probably means they'll need to replaced sooner.  Dennis gets water in the left tank of his Piper M600. His mechanic checked the cap, didn't find an issue, and swapped caps. Now both tanks have water. Paul said it could be that there's no new water, but leftover water from long ago. The water that collects sticks to the sides of the tanks and then rolls around as little balls until it finally makes it to the drain port. In other words, he suspects it's all old water that is just working its way out.  John has a borescope and he's wondering how to best put it to use. Mike mentioned Savvy's new borescope image collection efforts, and he refers to the intro, where they discuss the standard set of images. 

Mike, Paul, and Colleen help an owner with a bad lifter that shows itself after oil changes, guide an owner through a change his maintenance schedule, discuss what constitutes damage history, and take a guess at why POH numbers change over model years. Send your questions to 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: Steve has a 1975 Taylorcraft with an O-200. After oil changes one of his cylinders has some valve clatter. It tends to go away sometime later, only to come back after the next change. The oil filters are always clean and the oil analysis is good. Paul said there?s not much he can do about it, and Colleen said it?s also not a big safety of flight issue. Mike suggests they measure the dry tappet clearance to see if it?s wide enough to accommodate a larger pushrod to help eliminate the problem. Colleen said she read about a technique to fly it full power for an hour to see if resolves. They call it an Italian tune-up. Jim is on board with condition-based maintenance, and wants to alter the rubber hose component change schedule in his Rotax. Mike suggests that Jim can extend the change interval to maybe 10 years because he lives in the Midwest, and keeps his airplane hangered. The hosts discuss their method for inspecting hoses, how to manufacture them, and the various materials and considerations. Ken is considering a Cessna 180 with damage history. It was repaired and has flown 200 hours since repair. The damage history in question wasn?t so much damage as an improperly installed part that was replaced. Metal was found in the filter, a top overhaul was completed, and the owner is confident the airplane is running well now. Mike said the two things he needs to consider are whether the cylinders were reworked appropriately, and whether they were installed correctly. Considering it was a reputable overhaul company, the hosts are confident everything is ok to move forward. Scott wonders why on the same airframe, the performance speeds change over time. Paul guesses that early performance numbers were a combination of optimism, marketing, and guessing. And newer numbers are spot-on and well tested. Mike guesses that aircraft generally get heavier over time and maximum gross weights increase, necessitating speed increases.

Prop hubs that were nearly scrapped, how to properly measure the oil level, semi-synthetic oils, and tachs that don't agree 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 today at www.aopa.org/join Full notes below: Bill has a Cessna 182 with a prop that hadn?t been overhauled for about 7 years and 600 hours. This past March he had to send the engine off for some work, and he decided to send the prop off at the same time. They told him the hub was close to being trashed because of corrosion. He?s worried if he had gone another year the prop would have been scrapped, and he?s wondering what he can do to maintain the hub. Paul said he regularly sends out props that are 12 years old and he?s never had a hub rejected, but Colleen said her hub was rejected for corrosion. Mike thinks prop shops are zero tolerance outfits. He said just because they find something wrong with it doesn?t mean it was unsafe. Prop failures just don?t seem to be a problem, the hosts agree. The bottom line: don't send out your prop unless you absolutely have to. Tate is wondering how to accurately measure his engine?s oil level. He suspects that we add oil more often than is necessary because many of us check the level after flying, and seeing it lower, think that we?ve burned oil during the flight. Paul recommends picking a consistent interval to determine oil consumption, ideally at least 24 hours after shutting down. He said if you check the oil level right after shutting down and it says 6, you probably have 7 or 7.5 quarts. Mike said the only way to check consumption accurately is to check how many quarts you add over the course of an oil change interval because that?s averaged over many more hours. Rex is trying to avoid sludge in his engine and knows synthetic oils cause problems, but he?s curious about semi-synthetic oils. Mike said it?s more of a concern in Continentals than Lycomings. He recommends if Rex wants to do that he stick to unleaded fuel. He is considering running 50 percent mineral oil to compensate for the problem of keeping the solids in suspension. The original tachometer and the tach in Pete?s JPI run at different speeds. After many years of operation there?s now a big difference in time between the JPI and the mechanical tach. He wants to know which time to use for maintenance and aircraft valuation. Always use whatever time runs the slowest, Mike says. 

This episode is all about engines--how to fix one that runs rough, how to save money when buying one, why one went bad so quickly, and how to preserve one during a build. Email podcasts@aopa.org for a chance to get on the show. Full notes below: Brendan?s friend has a Taylorcraft with a tricky engine issue. It started with low rpms in flight, and has since been repeated on the ground. The mags have been rebuilt, both mags swapped, cylinders reworked, new carb swapped, new plugs, and they even bypassed the fuel system. Colleen suggests new plugs to ensure they haven?t been accidentally dropped or damaged. Paul suggests basic things such as the carb valve improperly moving. James and a few partners are looking at their first airplane. He?s interested in the costs and complexity of things such as retract versus fixed, constant speed versus fixed pitch, turbo versus normally aspirated, and more. Colleen said she recommends four-cylinder aircraft because of the cost and complexity. They all agree that constant-speed is a big improvement for not much more money. With retracts, insurance is a concern. Colleen said she paid a lot for maintenance the first two years on the gear, but it?s been otherwise trouble-free. Mike said turbocharging does add some expense. He said to budget to change the turbocharger once between engine overhauls, and maybe some additional exhaust system maintenance. Will found metal in his filter during an oil change and found a pitted lifter when borescoping, and is worried about a spalled cam. There?s only 200 hours on the engine and he flies regularly and uses Camgard. It did sit for six months during maintenance, but he had a dehydrator on it at the time. The hosts go through a complete troubleshooting and logic process to discover what might be wrong, and they plead with Will to get to his mechanic quickly before the case is split. Tim is building an RV-14 and just ordered his engine. He?s wondering how to keep it corrosion-free while he finishes the airplane. Their first advice is to follow the manufacturer?s guidance carefully to keep the warranty intact. It comes bagged with a desiccant pack that indicates if moisture levels get too high. But that system is only set up for a few months. Mike said you can only partially pickle it by swapping the desiccant packs, and maybe a dehumidifier. There are models that use desiccant packs, or an electronic one called a Black Max. 

How far can you go with preventative maintenance? The hosts discuss this, plus oil-soaked plugs, a strange fuel smell, morning sickness, and more. Email podcasts@aopa.org for a chance to get on the show. Full notes below: Lamberto has a 152 with oil soaked plugs, and is having to clean them every 25 hours. He wants to fix the problem, not simply deal with it. His mechanic suggests a harsh chemical. He?s tried new plugs without success, the hosts agree his BY plugs are the best for oil-fouling anyway. A solvent won?t help, Mike says. He suggests a ring wash, which involves filling the cylinder with a mild solvent, then pulling the prop through the combustion cycle. That forces the fluid through and cleans little by little. If you try to pull the prop through it?s probably too late and the cylinder needs to be removed and the rings probably replaced. Colleen likens it to flossing. Darin is curious about how far he can push preventative maintenance. His thinking is that if you can clean and gap spark plugs then you should be able to do the same to fuel injectors, and so on. Mike says it?s not entirely clear. The FAA has issued a letter of interpretation basically saying that the list in Part 43 is a list of examples, not an exclusive list. Cristopher flies a 172XP in a club in Germany and wants to fly beyond TBO, and also solve an oil issue. He thinks it?s coming out of the induction system drain. The only way that can happen is via the intake valve. They recommend borescoping the cylinder to confirm the leak. Callum has a Bonanza and smells fuel in the cockpit when transitioning to lean of peak. Paul suggests checking the throttle body area behind the panel. The mechanical changes when you lean can cause it. Mike knows of another airplane where this has happened, and they isolated it to a leak in the fuel selector. When you lean a bunch of fuel goes back through the return lines, he said, and any leak could show at this point. Jason has a 182 with an O-470 with a cylinder that is acting up on start when it?s cold. His engine monitor shows very low EGT when starting, and takes as much as a minute to 90 seconds to come to temperature. The CHTs are also much lower. The hosts agree that he definitely has the symptoms of morning sickness, and it?s time to ream it. 

How cold is too cold the fly? Mike, Paul, and Colleen answer this question, and help an owner solve radio problems, advise an owner to fix his probes, and describe the process to become an A&P in the latest episode. Send your questions and comments to podcasts@aopa.org for a chance to be on the show. Full notes below: Chad has a Cirrus and he?s looking for some cold-weather guidance. A mechanic told him that subzero temps aren?t recommended for a piston. The POH says that flights below -23 degrees Celsius need the cowl inlet plates. The hosts agree that there?s no problem flying in cold weather, but cold starting requires some care and preheating. Mike said the only problem with low oil temperature is that it doesn?t boil off the moisture, and low cylinder head temperatures could bring lead scavenging problems. Colleen said that lead deposits only matter on valves because it could prevent them from seating properly. But, that can be cleaned off if it occurs. Andy has an LX7, a turbocharged airplane. His TIT sensors don?t seem to be working. He?s been using CHT and EGT as a proxy for TIT and he wants to know if that?s a problem. Why not just fix it, Mike says. Andy said he is planning to fix it at the next annual, but Mike said to deal with it now. They recommend a range of troubleshooting options, but agree that it's not a probe issue. Darrell has a radio in his Ercoupe, but above 1,200 rpm it is static-y and unreadable. He?s checked the antenna, the coax, the mags, and more. Paul said it?s most likely a connection issue. He recommends starting with the Veclro microphone key switch. Next move to the microphone plug, which often oxidizes. The hosts also recommend checking the P-lead. Chase wants to get his A&P based on some of his own owner maintenance, refurb work, and building an airplane. He wants to know how to log his time. Mike said this is highly variable based on the inspector?s preferences, so he recommends calling the FSDO to ask what they want. When Mike went through this process he went back and recreated some of his previous experience on an Excel spreadsheet. Paul helps his employees get their A&P by recording the N-number, date, description, and time in a logbook. It?s important to note that there?s no calendar time limit of how far back you can go.

A compass that works on the ground but not in the air leads to a fun debate between Mike, Paul, and Colleen. Plus, the basics of lean of peak (again), jailbreaking a Rotax, and the liabilities of being a mechanic. Send your questions to podcasts@aopa.org for a chance to be on the show. Full notes below: Blake flies a Mooney that has a compass with a mind of its own. On the ground it works well, but in the air it vibrates a bit, but otherwise doesn?t move. Paul said his fuselage can become magnetized, which would obviously impact the compass. To solve this he says you need to degauss the frame. Mike suggests he start pulling circuit breakers to see if that fixes it. Colleen thinks it?s a current issue since it gets better when the RPMs decrease. With higher RPMs the wires in the airplane essentially become small electromagnets. Lenny is concerned about the liability of working as a mechanic in retirement. Paul said there is liability, but that the job is worth it. Mike says you either worry about or you insure against it. He describes his idea of a maintenance club. The concept is that a group of aircraft owners comes together and hires a mechanic who only works on their airplanes. The mechanic makes more money and the owners have better access to service. Andres flies a Bonanza lean of peak, and he wants to make sure he?s avoiding the red box. Mike said there?s a theoretical red box that only exists at GAMI on a test stand. Everyone else must use cylinder head temperature. With CHTs of 380 degree F, Mike said Andres is completely fine. The red box has fuzzy boundaries. He thinks of it as shades of alarm as you get closer to the center of the box. Colleen said her technique is to get on the lean side and just operate where it sounds and feels the smoothest. James has a Rotax 912iS engine on an experimental. It requires about 40 psi in the fuel system to operate. He thinks by updating the fuel computing he could lower the fuel burn, which is currently 4 to 4.2 gallons per hour. Rotax offers a higher level of controller that the hosts recommend he buy. They also recommend he leave the fuel system alone and work on another upgrade instead.

While one owner has too much of a good thing and lots of shops to choose from, another is second-guessing if the massive check to the cylinder shop was necessary. In this, our first crack at twice-monthly episodes, Mike, Paul, and Colleen spend more time as therapists and counselors than technicians. Submit your questions to podcasts@aopa.org for a chance to be on the show. Full notes below: Chris has a 182 with a recently overhauled engine that he?s concerned is making too much metal. In fact, the lab called after his most recent oil analysis to draw his attention to the report. The experts see the trends coming down a bit and think he really doesn?t have anything to worry about. With a clean filter inspection, they recommend keeping an eye on it and continuing to fly. Mike has a Malibu and he recently replaced all the cylinders and he?s wondering if he wasted his money. His oil analysis had high nickel, and he was experiencing oil pooling and low compression. He wants to know if he could have lapped his valves to save the cylinders. Unfortunately for Mike they agree that the valves would have been great candidates for lapping. Kevin has access to four maintenance shops on his airport. He has used two of them thus far and he?s wondering how to manage relationships and expectations when working with multiple shops. Mike said he?s a big believer in getting different sets of eyes on an airplane because each IA has his or her own style and focus. The disadvantage is that many shops will start from zero with a new customer, and doing the AD research and other items will take time and money. In Paul?s shop the IAs rotate airplanes, giving customers the benefit of multiple eyes under the management of one shop. He doesn?t recommend swapping shops every year, instead maybe waiting a few years. Steve has gone down the rabbit hole on the wobble test and he has come to the conclusion that the tool doesn?t really clear up the process. Paul said although he has a custom tool, he never uses it, preferring to just ream the guide and not taking the time to measure. 

Did Paul give us the definitive guide on how to hot start an airplane? Try his technique and see what you think. Also, unnecessary cylinder removals, a faulty tach, and a letter writer and guest who question if burping is safe. Send your questions to podcasts@aopa.org for a chance to be on the show. Full notes below: Walt has a Seneca and has had to replace three cylinders in the last five years. He?s concerned that his mechanic caused the problem after hammering on his exhaust to remove it. The hosts don?t think the incidents are related. While it?s not usually a good idea to hammer on the exhaust, they think it could be useful and safe in limited circumstances. Mike hones in on the reason for the cylinder replacement, and encourages Walt to be more suspect of the need to replace the cylinders in the future. Tim thinks his tach is off. He has an alternative device that also reads rpm that shows a different value, so he?s wondering what he can do to adjust or fix his tach. Paul said the tach is technically adjustable, but being an instrument, it?s not something an owner or even most mechanics can do. Unfortunately the hosts agree it?s time to replace it. Luke operates a few Extra aerobatic airplanes, and he constantly struggles with hot starts. He has been resorting to blowing large fans up through the cowling, but that?s not always practical. In a Continental it?s recommended to run the fuel pump for about two minutes to purge the hot, boiled off fuel and flush the system with cold fuel. Paul said his technique works on Lycomings and Continentals. Start with everything forward with the pump on. Then listen, and as soon as the flow stabilizes and sounds like it?s pumping liquid, you?re done. Mixture and throttle back, but keep the pump on. Crack the throttle, engage the starter, and then advance the mixture control over a few seconds. Thomas has a Mooney and he tried the burping procedure from a recent episode. But the next flight his attitude indicator didn?t come online, and he heard that turning the prop backward can ruin the vacuum pump. The hosts have all heard this concern as well, but Mike?s never heard a confirmed case that turning the prop backward causing a failure. Regardless, this seems to be an issue with older styles of pumps. 

Live from EAA Airventure 2023, check out our second in-person show. The questions come fast, and everything from proper leaning to oil leaks is covered. Can Oshkosh-goers stump Mike, Paul, and Colleen? Full notes below: The first question has Colleen in stitches. Can you widen the gap on your spark plugs to get more horsepower from an engine? Short answer? No! Don?t do it, the hosts agree. Even Colleen, who races airplanes at Reno, says she?s never heard of doing this. Richard has a 182 and says the book will allow for high rpm and low manifold pressure, or low rpm and high manifold pressure for a given percent power setting. He wants to know which is better for the engine. The hosts say that rpm puts strain on the engine, so they would choose high manifold pressure and low rpm. The idea of ?oversquare? is a relic and not at all true, they say. Julie has a 1979 Grumman Tiger and she wants the hosts to address owner-produced parts. Owner-produced parts must be made to the original spec from the manufacturer, which can be hard to track down. But, assuming the owner can find the spec, he or she must be involved in the manufacturing process. Ultimately it?s up to the mechanic to decide whether or not to install the part, and therefore take on all the liability. Bottom line is work with the mechanic early to get his or her blessing. Vedant asks how many more hours he can operate the 2,900-hour engine in his Bonanza. His engine has good compressions and only burns a quart every 20 hours. Colleen said conditioning monitoring is all about catching early indications of problems. Mike said there are only two compelling reasons to overhaul an engine. One is that you have solid evidence that there is something wrong in the bottom end that can?t be rectified without splitting the case. The other reason is that you can?t sleep at night. Terry has a 182 with an O-470 and can?t keep cylinder 1 below 400 degrees, even at altitude. That?s the right rear cylinder with a vertical baffle right behind it. He checked that. When it?s one cylinder Colleen said it?s usually airflow. Paul suggested a GAMI lean test and an induction leak test as well, just to be sure. Rex has a 182 and wonders about flying in the smoke that?s been prevalent around the country this year. The consensus is that smoke won?t hurt the engine, but changing the oil and induction air filter more often are good ideas. Tim wants to know about leaning his Mooney M20C. He wonders whether he should lean until it?s pretty smooth or really smooth. Mike said you have to accept a small amount of additional roughness if you want to run really lean. David has a 1979 172N and he?s wondering if he can use Camguard with his Lycoming 0-320-H2AD. Mike said he should use the AD-compliant additive just to remain legal. Greg asks for downsides to using variable-timed electronic ignitions in a carbureted engines. Paul said the risk is if they advance too far you can get into detonation. He recommends checking the cylinder head temperatures to make sure they aren?t too high. Advanced timing will show high CHTs and low EGTs, and retarded timing is the opposite. Jack has a Piper J-3 Cub with a Continental C-85 with only 40 hours. After flying he finds oil all over the belly but no obvious leaks. Paul said if the breather line is cut at the wrong angle it can actually cause a vacuum and draw oil out of the case. Mike said to borescope the cylinders with the intake valve open. It should be dry. If it?s wet you know where the oil is coming from. Mike asks about rpm on the ground and lead scavenging. The hosts say to lean as far as you can, regardless of rpm. Mike said not leaning on the ground is the biggest cause of valve sticking. Paul mentioned that Cessna now recommends leaning while at 1800 during the run-up and he said you can use that setting for ground leaning.

How to start an airplane, whether or not to wash an airplane for an annual, flying through smoke, and high TITs are all on tap for this grab bag of an episode, as Mike, Paul, and Colleen take your toughest questions. Write to podcasts@aopa.org for a chance to be on the show. Tony owns a turbo Twin Comanche with 300 hours on the engines. He burns about 14 gallons per hour on takeoff, but he thinks he should be burning 16 gallons per hour. As a result, he gets high cylinder head temperatures quickly, and needs to reduce power. He also sees power surging on the ground when his engines are hot, but not cold. Paul thinks the fuel servos and engine-driven fuel pumps are both in question. Colleen recommends pulling one servo and sending it out, just to see if it makes a difference. Paul suggests maybe a different shop to see if he gets different results. He?s had many experiences where there?s a problem with a component that overhauling doesn?t fix, despite the overhaul facility saying there?s no issue. Andy questions whether shops follow the regulation that requires an aircraft to be cleaned during an annual inspection. Apparently his shop said they will wipe off big globs of dirt, but don?t do a full cleaning. Paul said they definitely wash the airplane, but often it?s after the inspection is complete so they can see the various oil and grease patterns. The wash is complete, but basic. Really dirty airplanes are written up as a discrepancy so the owner can take care of it later. Matt has a 210 and he?s worried about exceeding the turbine inlet temperature. They try to fly it below redline, but they exceed it easily and quickly on takeoff. They are hoping to more aggressively lean and take advantage of low CHTs. Mike said not to worry about going over the TIT redline for short periods. Redline on the turbocharger is meant to protect the turbine wheel because the blades can creep from centripetal force when they get too hot. But flying lean of peak is possible because TIT is often exceeded only briefly during the transition, and not when settled. He also suggested that unusual TIT numbers can be a result of improper mag timing. Nathan is a flight instructor and wants to clear up the madness around starting carbureted small engines. He sees people use the primer, pump the throttle, and do all sort of other unusual things. He wants to know the right way to do it. Mike said that using the throttle, or using the accelerator pump, puts the fuel in the wrong place. He also thinks that if it?s possible, prime while you crank the engine for best efficiency. Paul said if the primer isn?t helping to start the engine, it?s quite possible the primer isn?t working. He finds a lot of the old primers are clogged, which leads to other techniques. Erik has a question about how smoke impacts piston engines. With wildfires being more and more prevalent, whether or not to fly during wildfire season is a growing concern. Colleen said she sees increased dirt in her oil analysis, her air filter gets dirty, and the leading edges of her airplane get dirtier. But the hosts agree that it's generally not a concern, especially for brief periods.

In two separate but similar incidents, owners want to know whether their cracked spark plug insulators caused pre-ignition or if detonation ruined their plugs. Mike, Paul, and Colleen tackle those questions, and many more. Email podcasts@aopa.org for a chance to get on the show. Full notes below: Mitch has a Mooney that developed a strong engine vibration a few minutes into a flight. He quickly discovered the problem as the cylinder head temperature was climbing, and he went full rich and reduced power. A subsequent borescope inspection discovered no anomalies, so he?s wondering what happened. Many people online said it was a clogged fuel injector, but Mitch suspects pre-ignition. So do Mike, Paul, and Colleen. They hone in on a cracked spark plug nose insulator. Mitch is also concerned about which came first. Did the broken insulator cause the problem, or did detonation break the plug? Thanks to good photos and data, the hosts are convinced there wasn?t a serious detonation event, and it was isolated to a plug problem. Brian wants Mike, Paul, and Colleen to comment on the validity of an unusual procedure. He has a friend that ?burps? the engine after every flight, and he swears it keeps his oil much cleaner. It works like this: after every flight the friend will open the oil filler cap and turn the prop backward. Every time he does it a bunch of gasses escape. It?s a legit thing to try, say Paul and Mike. Colleen is shocked because it seems an odd thing to do, but getting a lot of the moisture out?which is the majority of what is coming out?can only be good for the engine. Les has a Lance, and on a recent humanitarian flight with a plane full of passengers his engine started shaking badly. With no good option to set down, he reduced power and nursed it back to the airport. No borescope necessary here, the evidence was obvious?total piston destruction. Again the hosts suspect a cracked insulator, and again they think it was probably the spark plug?s fault, and not something that originated with detonation. Mike doesn?t seem classic detonation symptoms on the cylinder. Les isn?t convinced since his mechanic didn?t find a cracked insulator, something Mike doesn?t buy. Even extremely small cracks can cause problems, and with such a violent event, it likely would have been cracked in the process. Richard has a new carb temp gauge and he is looking for advice on how to use it. Specifically he?s found that in some phases of flight he has to have carb heat on at least partially to keep the carb temp high enough to stay out of the icing danger zone. But he?s also heard that it?s bad to operate this way. The hosts agree that doing so could be bad, but with the gauge in place he shouldn?t worry. It gives him the information he needs to operate safely. Jay discovered a broken oil control ring after just a few hundred hours on a cylinder, and he?s wondering if his operating procedure caused it. Jay flies a Taylorcraft and it has a new carb that enables leaning, whereas previously it was always flown full rich. Not to worry, say the hosts. Excessive leaning wouldn?t have caused the problem, and he should feel safe to continue leaning. 

Paul and Colleen broadcast from Dayton, Ohio, for Aviation Maintenance Technician Day, and together with Mike, do their best to help owners suffering with engine problems, mysterious cold air leaks, improper fuel indications, and more. Send your questions to podcasts@aopa.org for a chance to be on the show. Full notes below: Jim has a heavily modified Twin Comanche that blows cold air on the back of his neck, and he can?t find the source. He suspects it?s from the rear tailcone, but he can?t figure out how to stop it. Paul suggests it could be the rear bulkhead or from the wing roots. Despite his attempts, it?s actually gotten worse and is now blowing air on his legs that varies based on attitude, whether the heater is on, and maybe even heading. Mike suggests a camera and tufts of yarn in the tailcone to see where the airflow is coming from. Paul suggests that the airflow from the heater might be blocked, causing problems. They said if you pull out seats and floor panels on a test flight with a mechanic he might be able to find the culprit. Sam asks about dynamically balancing a propeller. When is it necessary? Who does it? The hosts agree it?s a good service to do when you change something, although the prop should be balanced from the shop. Arnold has a Bonanza that improperly shows the fuel level on the right tank, but only after it?s burned a few gallons. This is using Ceis fuel senders on a Garmin display. After many attempted fixes, it?s still reading low. Paul said they have to forget what they think has been eliminated and instead go and try to recreate the problem on the ground. Mike suggests putting a small vacuum on the tank to see if they can do just that. Keith has a turbonormalized Bonanza and wants to make sure he treats it well. He?s been surprised at how contentious the turbo versus non-turbo debate is. Mike said he thinks it?s a geographic problem where people on the East Coast think it?s useless and everyone out West thinks it?s a great tool. Although a turbocharged airplane is easier to abuse, the mechanisms themselves don?t have any inherent downfalls. So long as you treat it well and know that turbochargers are wear items, you should be fine. Ben has a Bonanza and he wants to know if he can remove the rear seats and remain legal by doing the weight and balance math based on station and equipment info from the manual. He also wants to exchange the fasteners to make it faster and easier. Colleen said a new weight and balance from an A&P is required once in order to be legal, and the hosts agree that fasteners approved for a later model Bonanza should be easy to get approved for his airplane. Kyle has a problem on both of his airplanes. His Cessna 182 with a bit more than 1,800 hours had a bent push rod and a bit of his lifter body had cracked as well. He is wondering if he should overhaul now since the case has to be opened anyway. Mike said the answer is always based on what happens after the case is split. If everything measures well then an IRAN is a good way to go, but an overhaul might be warranted too. It all depends on the inspection. The Continental C85 in Kyle's Luscombe has a stumble around 1,800 or 1,900 rpms. He thinks it might be a lean mixture issue because a bit of carb heat helps. Paul suggests he borrow a carb from a friend to see what happens. Even though Kyle has already overhauled his carb, Paul said he?s seen numerous times where even a supposedly overhauled carb won?t perform any better because they can?t duplicate the issue on the bench. A different carb would help to isolate the problem. 

A grab bag of unique questions come at Mike, Paul, and Colleen this month, including whether to buy new or overhaul, how prop stops work, what happens when you reduce from wide open throttle, and avoiding tiedowns. Submit your question to podcasts@aopa.org for a chance to be on the show. Full notes below: Dale has a Seneca and he?s looking to the future and having to overhaul two engines. He?s wondering how to decide between factory new, reman, or overhaul. Not surprisingly, they suggest flying your current engines as long as possible if they are treating you well. When the time comes that you have to change engines, Mike said his general rule is that if the engine has treated you well to consider a field overhaul. If there?s a concern about the current engine, he said to consider a factory engine. More control over the process is another reason to do a field overhaul. Jim has a question about his L-3 with a Continental A65. He has an updated carburetor with a mixture control. A challenge with that engine is that you don?t get an onset of roughness when leaning. It just tries to quit, and without an electrical system, an in-flight shutdown isn?t ideal. He?s worried that a big stumble is startling and he pushes it too far rich again, putting him in the red box. Mike said there?s no need to go to roughness. You can lean only to the first indication of power reduction. Dubs has noticed that after leveling in cruise, when pulling the throttle back from wide open, it moves a significant amount before the manifold pressure changes. Yet in doing so he?s reducing his fuel flow. He?s wondering why this happens. Mike thinks it?s possible Dubs has a carb with an enrichment circuit, which gives more fuel at wide open throttle, meaning fuel flow will come down as soon as throttle is reduced. The hosts discuss how Dubs? operating practice is how Cessna 182 pilots with 0-470 engines should operate to improve mixture distribution. The impact butterfly valves make is very non-linear, they say. The first 5 to 10 degrees of tilt won?t make a big difference, for example. Phillip is a maintenance tech in a shop that adjusted the low pitch stop of a prop based on the recommendations of the prop shop. He?s wondering why it was successful. Paul describes how a prop adjustment works, and why some airplanes don?t make full rpm until they?re down the runway a bit. Richard?s Rotax ran rough on a run-up, and after some troubleshooting he still hasn?t found the culprit. All winter it ran fine, but he?s concerned it will happen again in warm weather. Since this happened on both magnetos it?s likely not a spark plug. Colleen is wondering if the rpm range had an impact because the Bing carbs have three distinct operating ranges. If it happens again Colleen recommends isolating it and first checking the spark plugs, then maybe cleaning the carbs, and finally looking at the fuel delivery lines. Mike thinks it has to be a fuel system problem since it changes with temperature. Brennan has a nice Mooney M20J that he wants to continue to take good care of. He now lives in a very humid environment and can?t find a hangar. He left the airplane in his old hangar and can barely get to the airplane to fly it. He?s wondering what would be the least damaging practice?fly less or keep it outside. The hosts think it?s better to get the airplane closer and fly it while doing his best to keep corrosion away with freshwater washes, corrosion treatments, and maybe covers.

With two important airworthiness directives recently issued for Continental engines and Cessna Cardinals and 210s, Mike, Paul, and Colleen dig deep on the surrounding capacity and safety issues. Then they take calls on the limitations of engine monitors, and how normal can look anything but. Submit your questions to podcasts@aopa.org for a chance to get on the show. Full notes below: Michael has a turbonormalized Bonanza and he?s concerned his system isn?t operating properly. When full throttle on takeoff it overboosts, so he goes to partial throttle, which lowers the fuel flow. The controller and waste gate were both checked with no change. Mike says it?s a very bad idea to limit the manifold pressure with throttle. Continental says overboosting by 3 inches is a non-event. What is a big event is limiting fuel flow. The fuel flow is determined by the upper deck pressure, which could be adjusted. Either way, Mike says that Michael can leave it alone and give it all the beans. Paul is shopping for an engine monitor and is wondering if the hosts have any advice. Of course they do! Mike recommends user-programmable alerts. Otherwise they recommend you buy the one that best fits in your panel. A slew of recommendations on how to use it follow. Laurie?s engine runs roughly in a certain rpm range unless she leans to peak EGT. The hosts soon learn that she operates from an airport at more than 7,000 feet. Mike thinks it?s likely this is normal behavior because the engine runs too rich at full power at such a high elevation. John thinks he might be experiencing morning sickness on his RV-7?s O-360 engine. He is noticing an increase of lead buildup each time he borescopes it. The CHTs are also too low, at around 300 degrees in the winter. He felt the engine was running rough for a few minutes after starting, as well. The hosts look at John?s photos and think his engine is perfect. Paul mentions that so long as the valve seats well, the gunk in the cylinder is fine. They offer a number of ideas on increasing his CHTs. Steve is frustrated with his engine monitor because he's experiencing what he believes are nuisance alarms. The issue is that his engine manual and POH have different numbers, and the engine monitor is programmed with the POH numbers. The engine monitor can be reprogrammed, but it?s expensive and requires input from a mechanic. This is mostly an issue with engine monitors that are certificated for primary replacement.

Mike, Paul, and Colleen debate the difference between a bribe and incentive pricing, discuss how much carbon in the oil filter is too much, counsel an owner how to keep his alternator belt on, and reveal what's in their go-bags. Email podcast@aopa.org for a chance to get on the show. Full notes below: Jim is finding a significant amount of carbon in his oil filter after oil changes on his Cessna 182. He wants to know if the carbon is a problem. Mike said the carbon itself isn?t a problem, but it?s indicative of something else that is worth tracking down. He said the oil is getting overheated, carbonizing it. It?s most likely from excessive blowby. They recommend compression checks and borescoping to see if he can find the culprit cylinder.     John flies a Mooney with an electronic ignition system, and he thinks the airplane is slower since the system was installed. Mike thinks it?s possible it wasn?t timed properly. They see it often because the electronic ignition system is timed differently than a traditional magneto. If the EGTs are up and CHTs are down, that's further confirmation.     Jim is frustrated with the alternator drive belt on his 182. It comes off the pulleys about once every 10 hours. Paul said it?s very common. Counterbalances on the crankshaft are a potential problem, but a last resort. Grooves in the pulley could also be the culprit, as could excessive play on the shaft on the drive pulley. Paul also suggests trying a solid belt instead of Jim's current segmented version.     David is trying to make a kit of tools and spare parts to take while on cross-countries, and he is looking for recommendations. Paul said he has two criteria. First is something you?re willing to change. The second is to take any special tools or parts that most shops don?t carry. Mike said he takes common-failure items for the specific airplane. On his 310 he carries a vacuum pump, for example. Colleen said she always carries duct tape and tie raps, a screwdriver in order to take the cowl off, and a first-aid kit.     Dustin has a controversial question about a recent interaction with a shop. During the buying process of an engine overhaul, an owner found out a supplier offered the shop $2,000 to the shop if the owner went with them. The owner found out thanks to the shop's honest disclosures, but questioned if this is an ethical practice. Mike thinks this is no different than a wholesale/retail markup. Paul said he understands why this feels different, but he thinks it?s legit. Mike recommends asking your shop what they are making on your part, and if you?re not happy with the amount to negotiate it.  

This month Mike, Paul, and Colleen give an owner the ammo he needs to not overhaul his engine prematurely, help console an owner with super hot cylinders--maybe, console another with super cold cylinders, and give cover to a pilot who wants to refill his own oxygen. Send your comments and questions to podcasts@aopa.org for a chance to get on the show. Full show notes below: Pat?s Diamond has one suspect cylinder. The mechanic said it has failed inspection, and needs to be replaced, but the engine is beyond TBO and they are refusing to fix it without an overhaul. The question hits right at the heart of some of Mike?s frustrations with shops and their lack of evidence-based practices. He suggests lapping the exhaust valve to bring the compression back up, and then keep flying it. Kirk wants to refill his own oxygen system, but it?s not covered specifically in preventative maintenance regulations. The hosts asks if you?re allowed to add oil, fuel, and air to the various systems. Of course you can. It?s servicing the airplane. Mike says there is no talk of servicing in the regulations, but of course we all do it legally. They view adding oxygen in the realm of servicing. Robbie doesn?t believe his CHT gauge in his Socata TB-10. The factory single probe gauge shows 500 degrees and rarely goes below 400. He?s wondering what he can do to make himself feel more comfortable that it?s a gauge problem. Colleen asks if he smells anything. She smelled burning oil when hers went beyond 420. The hosts agree that given his great borescope photos, and good oil analysis that he?s probably ok. They also suggest checking the engine grounding strap that goes from the crankcase to the firewall. It grounds the engine to the airframe, and without it the probe wire could be finding some interference. The paint would also change color at 500 degrees. Will is seeing exceptionally cold cylinder head temperatures on his Comanche. On a recent flight to New York, he saw temperatures in the high 140s during descent. He knows his probes are good, so he?s wondering if there?s a lower limit and if it's hurting the engine. After discussing a number of possible causes, they discovered that Will is going full rich on descent, which is absolutely contributing to the low temps. Mike said that while you may have to enrichen a bit in the descent, if you forget the engine will remind you by running a bit rough. That?s followed by a detailed discussion of leaning for the climb and descent. Carl flies a Cherokee 180 and is wondering if flying it on cold winter days with density altitudes below sea level could hurt the engine. The hosts agree that the takeoff mixture setting is so rich that there?s enough of a margin not to worry. Detonation could be a concern in certain experimental engines, but a normal certificated engine has a big detonation margin. 

Did you know things live in jet fuel? These are the fun things you learn being a mechanic. Mike, Paul, and Colleen enlighten us on this strange fact, and tackle questions on leaning, burned exhausts, puddles of oil, and how not to set your airplane on fire when preheating. Email podcasts@aopa.org with your question for a chance to be on the show. Full notes below: Chris owns a Piper Comanche with 1900 hours on the engine, and it that has developed an oil leak of one quart every 2.5 to 3.5 hours. Fuel tank sealant and an air/oil separator didn?t work. Paul says there?s no way he is leaking that much oil from a leak in the crank case. He suspects another issue. Mike said Lycoming has a procedure to slather a sealant on the case seam. Since there?s a lot on the belly Mike thinks it might be going out the breather. He suggests a ring wash. Lance flies a Cessna 185 and is worried about his leaning procedure. He?s recently replaced all six cylinders and is concerned his leaning procedure may have caused some problems. He?s worried that by learning until roughness and then enriching slightly he?s in the ?red box.? Paul said if the engine is running rough, at least one cylinder has quit firing, so he's very lean at that point. Mike said the GAMI spread should be less than a gallon per hour. The GAMI spread is the difference in fuel flow between when the first cylinder peaks and when the last cylinder peaks. Assuming he only enrichens enough to stop the roughness, and no further, and his GAMI spread is good, he?s likely fine. If the CHTs are all below 400 degrees F and he?s less than 60 to 65 percent power, he has nothing to worry about. Chris number two asks about corrosion in fuel tanks. He works on turbine aircraft and often sees a brown staining on fasteners inside fuel tanks and he?s wondering whether it should be replaced. Paul said it?s only when the materials starts to degrade when you need to worry about it. He said a good rule of thumb is that if the part number imprint is still there that it can be left alone. Brad is wondering about pulling the prop through prior to starting. The general idea is apparently to move the oil around. Colleen said there?s no truth to any of it. You?ll scrape the oil off the cylinder walls if there?s any left. You can either preheat to heat the oil up on cold days, or you can pre-oil the engine if it?s been sitting a long time. Paul warns against pulling the prop through for safety. There?s no value in turning it backwards, and turning it forward can start the engine if you aren?t careful. Barry has a Tiger that had a muffler that lasted a long time when he ran rich of peak. Since running lean of peak or near peak his flame cones have burned out within 400 hours. Colleen talked to a local exhaust rebuilder who said he believes running lean of peak is burning up exhausts. It?s not because of the exhaust gas temperature, per se, but more likely the oxygen content of the flame at those mixtures. Jeff had a student with a Cessna 172 that he thinks has a tachometer from a Piper. It was replaced in 1993, and had been correctly signed off every year since. He?s wondering how that happens and what the pilot?s responsibility is in this case. Mike, Paul, and Colleen agree that an IA wouldn?t necessarily catch it on the inspection, although instruments and markings are part of the annual inspection checklist. Paul said he?s mostly concerned with the redline, and not necessarily the green arc.

Adam flies a Piper Warrior owned by his friend. On a recent flight he experienced some morning sickness that he was able to resolve. On a subsequent flight the owner had morning sickness as well. The owner is considering a top overhaul. Mike said he has two options, and a top overhaul isn?t one of them. The first is to do a wobble test and the second is to skip the test and go straight to reaming the valve guides. Paul recommends doing only one at a time. He said not to fly it again until the procedure is completed. They?re worried that flying it after the morning sickness could have caused damaged, so a borescope inspection is in order as well. AOPA r Kevin flies a Cessna 172XP that he suspects is the slowest one of its kind. It flies about 15 knots slower than book speed, and he?s seeking a remedy. Paul suggests first checking the rigging, specifically to make sure the flaps are completely retracting. If the flap rollers touch the end of the slots before the switch turns off, it will hurt the motor. But if there?s a gap after the motor has stopped, they aren?t full up. Totally ignore the fairing that?s riveted to the cabin, he said. He would also check the lifters to ensure complete motion. Mike suggests that is the airplane climbs at book values, he has a drag problem, but if it climbs worse than book, it?s a power problem. Greg is hoping to overcome the supply chain issues by purchasing a ?lifetime? oil filter. Being able to open the filter is the best thing you can do to know how the engine is wearing, Paul thinks. Mike thinks the filter inspection, while possible with a reusable filter, would be a messy, complicated job. Ken said he heard an adage that you should check your EGTs at 1,000 feet, and then lean in the climb to match those numbers, and he?s wondering about its validity. The hosts all completely agree, and it?s generally how they fly as well. Patrick flies a Cessna 170 and he?s wondering why his cylinders have a different CHT limit. Mike thinks the difference is probably due to the fact that CHTs are measured in a different position in his engine than others and the O-300 has a different cylinder design. After a cylinder swap he?s also wondering why break-in procedures sometimes call for changing power settings. Mike said he?s never seen a justification for this practice. He has broken in his engines by running them as hard as he could, keeping in mind cylinder temperature limits. Miko maintains his own airplanes and is looking for approved data. He?s struggling to find reasonably priced maintenance manuals. Clearly the manufacturer is the first place to go. Paul uses ATP for his airworthiness directive research. Typically they sell subscriptions, which are quite expensive though. He said you might be able to get a shop to give you their old paper manual because most have transitioned to digital. Colleen also uses McCurtain, which they don?t think exists any longer. Essco is still around and sells digital versions of scanned manuals.

Engines are the focus this month as Mike, Paul, and Colleen talk about valve failures, valve springs, burned valves, and more. And of course we had to have a leaning question. Send your questions to podcasts@aopa.org for a chance to be on the show. Full notes below: Marius owns a Cessna 172XP that routinely has a rough mag check on run-up. His mechanic is recommending fine-wire spark plugs after finding oil on the plugs. He has since bought them, which set him back more than $1,500. Colleen recently purchased some as well, and thinks they definitely work better. Nigel wants to get deeper into condition monitoring on his turbonormalized Bonanza, specifically with the turbo system. Mike said that the turbo controllers almost never fail. Waste gates are fairly problematic. Eventually they?ll start to stick, which you can tell by an inability to properly hold manifold pressure. The turbocharger itself is inspected at each annual. The shaft is checked as part of the inspection, and there should be a little wiggle in the radial direction, but none in the axial direction. Also look for blade scrape and cracks in the flange. Paul also recommends checking turbo system oil inlet and outlet check valves. Michael had a rough-running engine when he reduced power. They pulled the exhaust valve and found the keeper groove of the valve was much smaller than it should have been, and he?s trying to figure out what caused the problem. He?s now finding that the third cylinder is also behaving the same way. Mike thinks it almost looks like it?s been ground down. He suspects an installation problem. The hosts recommend pulling the valve covers and springs to check the rest of the cylinders. Viatcheslav is wondering about rotator spring failures and how they cause exhaust valve hot spots. He owns two airplanes, one with a Continental O-300 and one with a Continental E-225, neither of which have rotator springs. He's curious how and if his valves rotate without it. The hosts break the news that he does, in fact, own two of the few engines without them. He can continue to watch for hot spots on borescope inspections, and also occasionally lap the valves as a preventative measure. Reid is concerned about a burned valve on his 172. He leans aggressively, but doesn?t have an engine monitor, and wondered if his leaning led to the burned valve. His only source of information is the stock EGT gauge. Mike did some research on the Alcor gauge. Most of the Alcor gauges aren?t calibrated, and many don?t have temperature references. Some have an adjustable pointer that the pilot can set. Others have a calibration screw. On those, the manual tells you to lean to peak EGT at an altitude where you can get 65 percent power at wide open throttle, and then set the needle to match. Mike thinks the changes Reid is seeing could just be changes in the mechanism of the gauge. It?s not meant to measure absolute EGT. Furthermore, leaning doesn't burn valves. That's most often caused by a bad set.