Alternate Air Door?

[Doug Rohrer]

I did not install an alternate air door in the FAB on my RV-9A O-320 equipped airplane because I read that the components vibrate loose and can be ingested into the carb. The carb heat door provides an alternate source of air in most respects. Now I am facing the same question on my -14A build with the standard IO-390-A3B6 engine, which is still on order. Are there any concerns about the durability/safety of the alt. air door system on this installation? Being fuel injected, there is no carb heat option, so the alt. air door might be more important. I am wondering if this is an issue with you guys that have flying RV-14's. I need to know now while I can still install the actuation cable in the cockpit and through the firewall.

 

[wirejock]

Alt Air

I installed it on my 7A, IO-360-M1B.
I even managed to make it so it closes again without pulling the cowl. Of course, if needed, it's staying open till on the ground for inspection. Just sayin'.
Parts on the servo side are encapsulated with floxed epoxy.
It was just some pop rivet tails.

 

[Desert Rat]

I installed it in the snorkel on my IO390 as well. Pretty hard to see how it could suck anything into the engine if you build it as it's designed.

Like Larry said, the only thing on the inside is some rivet tails. In my case I just squeezed them so they're solid rivets.

 

[Reflex]

Doug,

For me, the answer is "yes" I need this. I hope to never use it, but it's there for a purpose. Van's doesn't appear to add weight or complexity to their aircraft unless they believe it's needed. However, being experimental, we're not required to install it. Personally I don't believe it will pull in any debris as the fit is good.

The recommended installation from Vans works, but it's not what I would call terribly robust or well designed in that once it's open, you have to remove the upper cowl to close it.

Our friends at TS Flightlines/Aircraft Specialty have a solution. I saw it at Oshkosh this year and thought it was a "must have". It allows the door to open and close enabling the pilot to close the door from the cockpit. I just finished the extremely simple installation and am very happy with it. Link below:

https://www.aircraftspecialty.com/rvproducts.html

 

[georgemohr]

I just ordered one of these upgraded doors as well.

 

[mburch]

The cable attachment piece posted above looks good. I did something different but not totally dissimilar for my installation:

Aside from how you attach the cable, another easy improvement is to add spring washers to the pivot bolt to help keep the door pressed up against the airbox instead of flopping outwards. This more than anything was the key to allowing the door to be re-closed from the cockpit in my installation:

Details here.

 

[mfleming]

I didn't add it to my -7 I0-360-M1B. I may install it in the future but I'm not yet convinced It's needed for VMC conditions.

 

[Nova RV]

If you fly in any rain the air filter is going to get water logged and the engine will go very rich from the reduced airflow. Been there and done that, you have to lean to get a decent running engine and subsequent reduced power from the reduced fuel. Opening the alt door is a safe solution and one that can close again after exiting the precipitation like the kit from Tom and Steve linked above is ideal.

 

[Doug Rohrer]

Now that I see the alternate air door on the vertical snorkel systems is different from the FAB's mounted under the engine on the carburetor, I will plan on installing it. I will also use the mod or order the system so it can be closed with the cable. At this point, I am hoping to receive my engine by the end of the year. Thanks for the help.

 

[PilotjohnS]

Mynproblems and solution

My alt air door gave me lots of trouble for the first few hours of phase 1.

First the door mount rivets pulled out of the airbox. I had to add a backing plate to the inside.

Second, the pivot screw kept on falling out. I went with a -3 screw, lock-washer locking nut plate and thread lock. After 90 hours still doing well.

Third, the pulled rivets would not sit flush to the mount and the door was held off from the mount. I countersunk the mount and used flush rivets.

Lastly, the door would open up in flight, so i repositioned the pull cable. And tighten the pivot screw. It will work once, but wont reset.