throttle back 912 uls rough

Re: throttle back 912 uls rough

by David Price » 8 years ago

David Price

1 11 0

Thanks Roger,
That makes sense, much thanks to everyone to help put this in perspective. David

Re: throttle back 912 uls rough

by James Ott » 8 years ago

James Ott

22 342 411

I think I disagree with Roger. Without a check valve, on the ground with engine off, fuel will flow backwards, bypassing your fuel shutoff valve, into the carburetors. So for maintenance purposes you will have no way of completely shutting off fuel to the engine. Remember, the header tank, where the return line terminates is constantly under a pressure equal to the head of fuel up in the wing tanks, which is always above your carburetors. The Rotax installation manual calls for a check valve. You must use one without a spring so it opens easily when engine is running. I mounted mine in the return line where it turns up almost vertical into the header tank fitting. This way, gravity keeps the ball on its seat when engine is off-no leakage.

Re: throttle back 912 uls rough

by James Ott » 8 years ago

James Ott

22 342 411

I am assuming a high wing type plane. A low wing may not need the check valve.

Re: throttle back 912 uls rough

by James Ott » 8 years ago

James Ott

22 342 411

I was wrong about Rotax calling for a check valve in the return line-they don't say. However, my argument still stands. My Kitfox build manual DID call for a check valve in that line and it is part of the Kitfox return line package.

Re: throttle back 912 uls rough

by David Price » 8 years ago

David Price

1 11 0

Thanks James,
I ordered the return line kit from Kitfox, and it does come with a check valve. Looks like they do recommend it. At least partly because of fire, without a fuel valve to shut off, there would be a constant flow to the engine compartment in the event of a post accident fire. I like your location for the valve, makes sense. Much thanks to everyone on this subject. David