alternate air

[Tom Martin]

While fitting the alternate air door, as supplied by Van's, I was not enthused about the inability to close the door once opened. While I realize that this door is meant to be used only for emergency reasons It would be nice to be able to open and close it to verify that it will in fact work. As shipped it might be able to be closed in flight but I suspect pressurized air would not allow the door to be reseated in the proper location.
To keep the door moving in the right direction I fashioned a guide that captures the door as it swings open. This should allow the door to be reseated in the proper closed position. A scrap of .063 was cut to the right arc and was used as the spacer. Fight testing will follow later this year.

[/IMG]

[/IMG]

 

[erich weaver]

I remember seeing a website offering a different style alt air door that was closeable for sale. The Vans style seems to not be that robust. Could probably track it down if your interested.

Erich

 

[molson309]

Nice job Tom! I have the same alternate air door on my Rocket (and RV) and have been looking for a way to capture the door for the same reasons; you've found a simple and elegant way to do this.

Now all I have to do is figure out a way to quickly disconnect the cable on the Rocket to allow cowl removal!

Mark Olson N407V RV-7A N16XV F1-EVO Rocket

 

[azcloudflyer]

I didn't like the pull once system either. What if I want to try alternate air in flight to see if it calms a rough running engine? I only get to try it once and then I'm stuck wit it? This is what I came up with. The hole on the far right is for a cushion clamp to hold the control cable. Looks like your solution would be a little lighter.

Other pictures are on my firewall forward page:
http://www.azcloudflyer.com/fwf.html

 

[9GT]

For the alternate air on the Cozy MKIV, I layed up a fiberglass disc about 8" diameter layup on the bottom of the air-box with a release agent. After cure, I drilled a #12 pivot hole in the center. Then I drilled four 1.5" holes @ 12/3/6/9 clock positions through both the lay-up and the filter box and popped it off. Those matched holes became the alternate air source in the "Open" position. An AN3-5? bolt was glassed in the air-box pivot hole and a bronze bushing in the cover pivot hole. One thin plastic washer between the air-box and cover and one between cover and nut provide a nice smooth pivot action. I fabricated a metal wire control anchor pivot and milled an arched slot in the outside edge with a metal post (AN3 bolt with threaded portion removed) glassed in the air-box. This provides a positive "Open/Closed" position. It is a very lightweight assembly that works very well ( over 300 hours). In the Cozy, that area is a high pressure area because of the updraft cooling design. It gets opened at cruise and the EFIS shows almost a 1 psi manifold boost. I plan on a similar system on my -10. Wish I knew how to post a pic,,,, Folks who have seen it really like it.

 

[N427EF]

Needed or not?

The "alternate" alternate air doors all seem like good designs and I am sure
they will work very well.
I have given this some thought and come to the conclusion that this door simply does not need to be opened and closed except maybe once to see that it works.
On my 8 where the alternate air door could be opened and closed I remember doing this once or twice in 450 hrs of flying.
Looking at the 10 design you could simply pull the alternate air door for an operational check before you do an oil change, and then reset it when the cowling is off. This could be done while you approach the airport to be sure it works as it should while in flight.