FAB bypass

[Skint]

On my carbed 0-360, 7a, should I install the Filter Bypass? I do not intend to fly into known icing.

[jeffmoreau]

I installed the alternate air door on my RV8A with the FAB. Even if you are not planning on flying in icing conditions, I feel it is good practice. Your air filter inlet could become blocked by a bird strike.

[Lycosaurus]

I had spoken to Van's engineers about that same question. when I was building. They had just introduced a free retrofit kit. They mentioned that there was an occasion where the fab had swallowed a garbage bag (or some similar debris), resulting in an air intake blockage, and subsequent engine stop.

I decided it was worth the extra effort to install.

[sprucemoose]

Tom (and all),

The Van's FAB bypass has nothing to do with carb ice. It bypasses the air filter in the event that the filter or inlet become blocked. Deploying it in carb icing conditions will likely make the problem worse and not better.

The first version of the bypass was poorly designed and a potential hazard. The second version looks a little better, but I elected not to install it. The hazard that it was meant to deal with, an air filter blocked by snow, is easily dealt with by proper application of alternate air/ carb heat.

I wouldn't install it.

[N941WR]

Originally Posted by Lycosaurus

I had spoken to Van's engineers about that same question. when I was building. They had just introduced a free retrofit kit. They mentioned that there was an occasion where the fab had swallowed a garbage bag (or some similar debris), resulting in an air intake blockage, and subsequent engine stop...

Did this happen close to the ground? If so, I doubt the pilot would have had time to open the alt air before the crash.

Originally Posted by sprucemoose

...The first version of the bypass was poorly designed and a potential hazard. The second version looks a little better, but I elected not to install it. The hazard that it was meant to deal with, an air filter blocked by snow, is easily dealt with by proper application of alternate air/ carb heat.

I wouldn't install it.

Based on what Van's sent me for my replacement FAB, they are up to design #3. Still, I see no need to install it for a VFR aircraft.

I have flown through snow VFR and simply pulled the carb heat on before entering the snow and didn't have a problem.

This is PC (pilot's choice), you can add it if you like.

[Lars]

In this long thread are some pix of sliding alternate air doors. Seems like a more reliable design to me, with the added benefit that they can be closed again from the cockpit- though I suppose if the door is needed because of a blockage then the FAB should come off anyway to verify that all of the offending blockage has been removed.

[aerhed]

This is Van's slide door converted to a magnet pop-off like C-200's navajos, etc. That's all I'm using. No front door to fall apart, no cables, no heat (IO-540).

[aerhed]

Forgot the picture.

[LifeofReiley]

The newer system works well, just DO NOT rivet to the FAB (Fiberglass) use screws, loctite and steel lock nuts when doing the install. The rivets will work the fiberglass and could end up sucking through. With the loctite and steel lock nuts you should be good to go. If you elect to rivet, put a backing plate in on BOTH sides.

[Lars]

Originally Posted by aerhed

This is Van's slide door converted to a magnet pop-off like C-200's navajos, etc. That's all I'm using. No front door to fall apart, no cables, no heat (IO-540).

More information please, if you don't mind. I'm not familiar with the magnet popoffs of C-200's or Navajos. Looks interesting.

Thanks!