"Shock cooling is a myth"

Engines fail when they're new, not old. Plus, leaning with carb heat, questions to ask as a renter, and Cirrus cylinder cracking. 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: Kevin is looking to rent an airplane from a private owner and he's looking for opportunities on Facebook. When he goes to see the airplane and meet the owner, Kevin is wondering what he should ask. Paul suggests staring with the logbooks and looking for the annual inspection sign off with a note that the ADs have been complied with. Colleen says to start with the books and then go through a thorough pre-flight. If the owner balks at repairs that you consider essential, she suggests walking. The hosts debate the importance of how many people fly the airplane, but settle on the fact that what really matters is a standard squawk sheet. Alan is concerned about the new Cirrus service bulletin that describes cylinder cracks on Continental engines. He asked the shop to inspect per the service bulletin and the shop found a crack where the SB describes. Paul said all you can do at this point is to inspect it frequently, ideally every time the cowling is off. The manifold pressure pull and other pilot actions won't impact this. It's a design defect that has nothing to do with pliot actions.Ike flies an O-200 and he thinks it runs better lean with full carb heat on while in cruise. He's wondering if the unfiltered air is bad for the engine. The hosts say so long as he's only doing it in cruise, it's no problem. Colleen does this with one of her airplanes and her oil analysis doesn't show any additional silica in her oil. Mike suggests he try partial carb heat to get the same effect.Lawrence and his son fly the family's new airplane. He wants to instruct, and his son wants to fly for a career. They've flown 400 hours or so, and the engine is around 2,000 hours since TBO. They do a lot of their own maintenance under supervision, and as Lawrence learns more he wants to be sure he is being safe. Specifically he's looking for signs of when to start worrying about TBO. The engine that you have is more reliable than what you're going to have after you overhaul, Paul said. Colleen mentioned new, defective parts on new engines. The team focus on maintenance-induced failures, etc. The most common reason the engine will need to be overhauled, Mike said, is if the cam and lifters are doing bad. This will show in metal in the filter. But these issues aren't safety issues so much as financial problems. It's about a bulletproof an engine as you can get, Mike says. Accidents caused by engine failure almost always occur when the engines are young, not old, according to Mike. Lawrence wants to focus on what really matters. Mike says there are three things--boroscoping, checking for metal in the oil filter and screen, and watching for symptoms of morning sickness.