ORIGINAL: Rick.
I use a Spektrum 2.4 Module in the back of my trusty Futaba 9c - so only the throttle channel shuts down if the tx signal is lost - and if the receiver failed (ie, no power to the servos) it looks like the kill switch would remain 'on' thus ensuring my plane went in under power - great - NOT
I'll assume you set the ign kill up on ch 5. Have you tried setting it up as if it had 'failsafe' ability, and set 'failsafe' to a big negative value?
If you can't do that, then it's that Spektrum (JR) module holding you back.
I just yesterday, went trough all my glow & gas models, checking and setting 'failsafe' on all. Found I'd missed setting 2. One was on ppm(fm) not pcm, and normally you can't set failsafe on a Futaba Super 9CAP if it's not pcm. Well, I set it up in the tx as if it were pcm and had failsafe ability, then reset to ppm, turned off the tx & ....tada...it worked. It was a glow and all it did was pull the throttle back to kill the engine, after the tx was switched off.
Various Futaba TX's on 72 mHz don't even show you the 'F/S' feature unless it's set to PCM.
My futaba 10CAP w/2.4 gHz module DOES show 'F/S'.
Probably got to be something bad about that, but what?
Shoot, it worked!