Alternate air door question James cowl

Charles in SC · #1 10-19-2015, 09:24 PM

I flew a Comanche 260B for years. It had an alternate air door that was held shut by a magnet of the type used on kitchen cabinet doors. Has anyone used this on an rv7 with an IO360? It was very simple and worked when it needed to. I had 2 times that I got iced over and the door opened. You lost a good bit of power until the engine had enough suction to pull the door loose from the magnet.

airguy · #2 10-20-2015, 08:57 AM

The cowl and FAB instructions from James shows some decent pictures and build instructions for putting in the alt air door, but leaves the method of actuation (spring, cable, magnet) to the builders choice.

N941WR · #3 10-20-2015, 09:11 AM

Yes, the cabinet magnet used to be standard fair, but then people would ingest them into their engines when they would break loose. Needless to say, they aren't used much any more.

I didn't bother installing an alt air door on my VFR ship and in 700 hours of flying have never wished I had one.

cajunwings · #4 10-20-2015, 10:22 AM

Most fuel injected Pipers have a alternate door incorporated into the lid of the airbox or somewhere along the inlet duct. They are automatic due to the magnet & spring arrangement & usually have a push/pull cable for manual override. My IO-320 engine came from a Twin Commanche and I will be transplanting that alt air system to the bottom of the Vans airbox. If you can find a Piper with the cowl off check out how they did it.

Don Broussard

RV 9 Rebuild in Progress