Alternate Air and Vans FAB

[McFly]

Let me preface this question with this: I am a VFR weather weenie type of pilot and don?t plan to fly through rain much less snow.

I?m just wondering what everyone (ha) does/ is doing about the alternate air in Vans FAB. I am considering not installing it, particularly since the new method involves routing of an additional cable (that is my impression anyway). Here are the particulars of my project: RV-7, O-360, with Vans FAB and carb heat kits.

I am interested in what you other guys have done and your rational behind your decisions. Thanks

[Build9A]

I didn't install the extra alt. air door on my FAB airbox. I did install carb heat. I am also a VFR only pilot and promptly turn around or land if I find unpredicted bad weather. Hard rain, thunderstorms, ice, and me don't mix. I built mine VFR and it's going to stay that way and so am I. Don't feel like a VFR weeny. It's a lot more fun to fly VFR (IMHO) and there are more VFR days than I can afford fuel for. Jack

[gmcjetpilot]

The first attempt with the magnets was clever but never installed it and thought it would be problematic. I was right and van now has a cable deal according to the SB of Oct 2005.

http://www.vansaircraft.com/pdf/Fab-sb_05.pdf

I am not installing that either. I am like you and do not plan on flying in "Heavy snow, freezing rain or icing conditons"; I doubt rain or light snow would be an issue. However I suppose the rare bird stuffing itself into the scoop could happen. Don't laugh; it has been documented once in the RVator years ago. It happened to an unfiltered airbox RV, plane continued to fly but roughly, the bird (or part of it) made it all the way into the carb throat!

I guess the original push for this was for a RV flying in snow. Even the SB implies it is optional mod if your intended flight mission does not include flying in a snow storms.

I am leaving it off. If I suspect a blockage problem I will pull the primary alternate air door and block the scoop off proactively. G

[L.Adamson]

I live around mountains, snow, and birds...

I removed the magnetic version & installed the new cable setup. Was not too difficult, and I'll feel better if it's a last ditch effort to get some air to the carb!

L.Adamson -- RV6A (will paint sometime & put back together)

[sf3543]

GMC's comment about the rare bird in the scoop reminded me of something that happened a few years back in my RV6.
Just after take off, I noticed that my airspeed had gone to zero. I thought, darn, I forgot to take off the pitot tube cover..... but I remembered taking it off, so........around the patch and land.
When I inspected the pitot, VAN's tube type, I found the front half of a dragon fly and what was left of his wings sticking out of the tube. It pulled right out with no problem, though!
We laughed about that one for a while!

[Bob Axsom]

I installed the magnetic latched by-pass door and reported the failure and my fix in this forum. I got the new design but I haven't overcome my aversion to installing and routing another cable yet, etc. etc. In the information I have read about the justification for the new design Van's says they found that under certain conditions the door was opening unnecessarily and reducing performance. My new mount for the magnet will not fail but the "opening unnecessarily and reducing performance" is bothersome to me. I wish I had more data on the "problem" but I don't and wanting all the performance I can get I will probably make the change someday or "lock it down" for special occassions like AirVenture Cup.

Bob Axsom

[McFly]

FWIW: I call Vans about this and the tech help guy said he didn't put it on his plane.

One less thing, thanks again.