"Placard it inop"

Ask the A&Ps

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 [e-mail] for a chance to get on the show.

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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.