Alternate Air Door Control

Time: 2 Hours

An alternate air door is a small sliding door that gets mounted to the side of the fiberglass “snorkel” that funnels air to the fuel injection control. The idea is that if your air filter would get clogged with anything like ice, which would restrict needed air flow, you could open this door and allow unfiltered air to get to your engine. You don’t want to run like this for a long time as the air is unfiltered but it allows the engine to keep running while you get it on the ground. I won’t. E working on the actual door for sometime but I wanted to get the control in now while I had the top skin off. I ordered my push-pull cable from MacFarlane aviation just like my cabin heat, I’m so thankful to have attended flight training naperville il, now I get to experience all of this fun. I drilled the holes and ran the cable to check fit, once I was happy I decided where I would have it exit the firewall. I looked at a lot of builders photos to see what they had done. It’s hard to know exactly where to put it so that it would line up since I don’t have my engine so photos are my best friend. When I was happy with the placement I started to process of adding the cable pass trough I purchased from Aircraft Spruce. This “ball” style pass through gives you the ability to angle the cable as needed as well as give you a really secure and fire proof connection. First up was to mark and drill the six screw holes and center hole.

I then used my hole punch to open the center hole to 1 1/8″. 

With all the holes and edges deburred I put the backer plate in position with the top and bottom screws. 

I then ran the cable through all the holes securing it with the washer and nut in the gear tower. Once it is through the firewall I place one of the retention rings followed by the two halves of the center ball followed by the second retention ring and screwed them all together. 

I really like these pass thoughs and they really look clean. I will use three more when the time comes for the throttle, propeller and mixture. While I was in the area of the the cables I decided to do the EGT/CHT cable extensions. I had ordered extre cable from Dynon since the cables only made it out about 6″ on the firewall and need to get the left side of the engine. Since I had to splice these I decided to do it inside the fuselage to be a cleaner look and be out of the engine environment. 

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