Carb springs best position options, full or idle?

Paul

The Rotax default is fail to open, not idle.  The reason is simple, full throttle the engine will continue to run and get you back to the airport where you can set up for runway then shut off the engine...no landing off airport needed.  

The prop should be you governor to control the engine speed, if you have a fixed prop and set it correctly to not exceed the limits.  This process is rooted in the FAA guidance (EASA also) that states it has to fail to a running mode for safety.  That is the requirement for certified and frankly I think the safest way.  

Cheers

hi Paul,

 Like RW said they are set in the fail open from Rotax and almost all the planes I see are set that way. Only a few are set to close. Think of it in a practical mode. 

If it is set to open and a cable fails then that carb will go wide open and then you can advanced the throttle and the other car will be wide open and you could fly to a safe place to land. If they are set to close to idle then there is nothing you can do, but pull the other carb back to idle you you don't trash your engine and you're going to land right there. Did I mention you're over the Grand Canyon. 😂

Yes that makes the most sense for sure. Funny how most engines I get are set to idle. My fleet is fuel injected but I still get plenty of carb issues.

Everything said above makes perfect sense, and I agree with it.
There's another useful thing about this spring: it pulls the cable, eliminating the play between the sheath and the cable itself during normal operation.

Roger, I thought of you, last month , I visited Pima Airforce Base...😀

Jacques ( and Google translate )

Hi Jacques,

You should have called and stopped by.

p.s.

The springs work better on thinner cables vs really thick cables that may have too much friction in their sheath and bends in the cables can play a part if they are bent too tight.