I've got one plane with a throttle and choke kill, two others with fiber optic kill switches, and a couple with just the throttle trim as a kill.

I've never had a problem with the EDR Fiber Optic Kill module. They are installed on a 40% Carden Giles 300, and a 40% Carden Extra. With the ignition kill switch, I end up having three ways to to kill the engine. The ignition kill switch, the throttle trim, or the switch mounted to the fuse for the ignition battery.

With the choke and throttle setups, I also have three ways to kill the engine. The choke servo, the throttle trim, and the switch mounted to the fuse for the ignition battery.

My favorite method is the ignition kill, with the throttle trim as backup, and the physical switch for the ignition battery. This allows two ways to shut down the engine that are independent of each other, as well as a manual shutoff on the ground for the person holding the airplane which is also a positive shut off.

When using only the choke and/or throttle kill, you only have one method of shutting off the engine while in flight, which is carb/throttle related. I had an interesting 28 minute flight a couple years ago because my transmitter ignition kill setup failed (not the fiber optic variety) and I bypassed it for the day, thinking what are the odds of having the carb/throttle kill method fail as well. Would you believe, it failed also.

Basically, the muffler came off, which changed the engine dynamics enough so that I couldn't use the trim to kill the throttle. I've also seen motor mounts loosen up and cause a similar problem on other peoples planes, where they couldn't kill the engine either because the linkages didn't work properly. One resulted in the engine departing the airplane while in flight with the expected results, totaled. The other ended up with a high speed landing which resulted in significant but repairable damage.

Here is the full story from my web site...
http://host64.ipowerweb.com/~giantsc...min_flight.htm or at http://host64.ipowerweb.com/~giantsc...nical_main.htm under kill switches.

Because of those incidents, I always use two independent methods to kill it from the transmitter, along with the standard ground accessible fuse mounted switch. One method is carb shutoff being throttle trim and/or choke. The other being electrically driven on the ignition battery or magneto via a fiber optic setup or servo/switch setup.