I can tell you for sure which way I want the butterfly or slide in my carb to fail if the cable breaks or lets go... wide open. On an early dual training flight in a Citabria, after climbing out on takeoff I proceeded to reduce throttle to cruise setting for the pattern and nothing happened. Moving the throttle knob in and out had no effect on the engine RPM or sound... it was WOT. Student pilot (me) sat there without knowing what was going on or what to do, whereas good old Charlie instantly knew what was up and sounded off with "I've got the airplane". He completed the pattern with the throttle wide open and used the mixture to control power, called the tower for an immediate priority to land, blipped the power off and on while on final to maintain glideslope after a circling approach (not squared-off), and only moved it to idle cutoff in the flare to reduce float. After the rollout off the active, we got a ground tow back and examination showed that the bug nut lockscrew on the throttle cable had loosened (Bowden-type throttle cable).
As others have said, if the slide or butterfly closes, there is no option but to set up best glide and prepare to land. And funny thing about slide-type carbs on most two-strokes (Mikuni, etc.)- by the nature of their design you'd have to change the whole setup to make them fail open because the cable pulls them open against a spring. Interesting design problem, but not impossible. Oscar Zuniga San Antonio, TX mailto: taildr...@hotmail.com website at http://www.flysquirrel.net
