RE: Smart fly optical ignition cutoff setup
There are conditions in which no matter what the cut-off wont work! If the RX goes into a crazy state (i.e. the processor fails or some other catastrophic failure - but it retains power, the cut off will be rendered useless and the ignition will remain hot while the plane heads for impending doom. If the RX goes into freq lockout, programming the fail-safe feature to cut that channel would immediately kill the engine.
At a minimum the fail-safe should always be programmed to cut the throttle servo to a bit above idle so it can't fail in WOT under any but the most extreme circumstances. The kill switch should only be a backup.
In the case of the bad crystal, if the RX had fail safe and was programmed correctly, the engine would have at least cut to idle.
I never program my cut-off to change states in fail-safe. Bad enough I ever get a temporary lockout - I don't need a dead stick right after recovering from it!! I set my throttle fail safe to a high idle on lockout.
Of course all this assumes you have a PCM system or at least a programmable throttle servo (Hitec) .
DP