My take on Optical Kill switches is a bit different than others. I use and highly recommend the Tech Aero IBEC. It's device that connects toa convenientRX port like retracts. It connects to the CDI and powers it directly from the airborne battery. It saves a lot of weight (second battery and switch harness) which helps smaller gassies.

This thing gives you remote control over arming and disarmingyour ignition. Very convenient and safe. All ofmy gas planesare set-up this way.... Cost is moderate at around $40, directly from Tech Aero or distribution

If you have a throttle malfunction in the air ,closing the choke may or may not stop the engine. It depends how open the throttle is.
To use it to stop the engine on the ground for safety in the event of a runaway, etc...is not a good idea.

I've seen an engine running on choke run long enough to shoot across the pits and take a chunk out of a chain link safety fence.

The fence did its job, the choke however wasn't seating correctly.

THATwas a "poorly-tuned engine", to be sure!!!!!

Wow. Who would have thought this would be such a hot topic. I'm seeing that there are many different ways of killing a gas engine. Some better than others, but every one has their own ways of doing things. I chose to go with the opto, and it does just what I want it to do. Thanks to every one who took the time to answer my questions. Steve.

Steve, hang around here for a while and you'll see many conversations like this one. Some maybe not so civil, some can be really long. Most though, very educational if approached with an open mind. Welcome!
-Al

I don't want a momentary loss of signal to kill my engine. What if I get control back and the model is too far downwind to glide back to the field? I would rather that the fail safe reduce the engine RPM to low idle.

CR

One of the things i Like with the opti kill, is I can toggle the switch and hear if the plug is sparking. Kinda nice if the engine is being finicky and you need to verify spark quickly. Then I know I need more prime or I am flooded.

I would always rather err on the side of a dead engine. If you're experiencing enough signal loss with a modern radio to invoke fail safe, you're probably not going to get signal back. If you are getting yourself in that situation where it comes and goes, then your power system is probably inadaquate for the flight load.

But if thats your choice, then setting the proper fail safe will give you what you want, kill -on/throttle - low

My experience with Fail Safe setups has proven to me that it only really creates an illusion that the pilot *may* regain control before the crash, or during it.
A "sort of" properly functioning radio is really worse than one that just dies, at least from my experience.
Fail safe if "intermittent" could leave you with a killed engine, and no means of restarting it if you did "get it back". I prefer that a radio failure just crash the thing, ending any doubt.

Older thread but good topic. I'm new to gas too. I have a DLE 30 and a Spektrum DX7s. There is only throttle return on failsafe. What I did was a combination of things mentioned above. Great planes mechanical switch, re soldered to N.C. as above, operated by throttle servo arm with dubro servo saver spring installed to allow servo arm movement beyond throttle stop position. This cuts power to optical kill switch. I had to bind the receiver with my throttle trim all the way down (enough to actuate the mechanical switch). Then set the idle trim after binding. I then set my throttle kill to work off trainer button (-20%) to kill the engine on the ground.

This set up allows me to keep the throttle stop and return spring on the DLE carb. Kill the engine conveniently with trainer switch at any time and kill the engine in case of signal loss. If the servo fails I'm out of luck, but I could kill it even if I lost the whole linkage.