i am not trying to force an issue but
lets analize the options
1. fuel supply shutoff, takes several seconds to min or so for the engine to stall, probably not useful
2. fuel rack shutdown,, effective 99+percent of the time, unless the rack gets jambed or the linkage fails or binds, or electrical fault
3. decompressor, effective 99+ percent of time, may cause damage to engine if the engine is over rpm (runaway), possible linkage binding, electrical fault, etc.
4. air shutdown, 100% effective and is tested each and everytime the engine is run (by design), failure mode, failsafe to engine stall, electrical fault results in engine shutdown.
things to consider, the need for emergency shutdown is of course of those rare times something is going very wrong and this is usually the time that one gets pumped up
with adrenalin and cannot think clearly, this is not the time that you want something that is supposed to help you go haywire and require thought, fiddling or repair.
you want it to work 100% of the time, everytime without input from the operator, other than a panic button that is bright red and easy to reach.
in my opinion
bob g
bob g