I do like using optical kill switches, even though they add something else that can fail into the plane. I will give one example of a situation where an optical kill switch was very helpful to me. I was flying a 1/4 scale ME109G (about 34 lbs) when I noticed the engine would not go below around 4000 rpm, even when the throttle stick was at the idle position. It otherwise acted normally and I had full throttle control above 4000 rpm.

I flew around for a while at different throttle positions thinking about what to do and actuating the throttle to see if I could free it up and the problem persisted. To land the plane I put the gear down, with no flaps and brought the plane in over the runway. I did one trial pass to check the speed. On the second pass I used my optical kill to kill the engine just after the plane had passed over the end of the runway with the plane about six feet off the deck moving at good speed. I was able to successfully deadstick the plane from that position. Had I not had any type of remote kill, I would have had to fly high and wait for the plane to run out of gas and then deadstick it from there. For me, this approach is fine for many planes, but with this particular warbird, I much prefer to land under power. They can be hard enough to land when everything is working perfectly!

I found out after the plane had landed that the vent line had worked forward into the cowl from vibration and was behind the throttle arm preventing it from moving to idle. A very rare situation that will probably never occur again, but at the time I was glad I had a remote kill method so that I could kill the engine at just the right time on landing.

As for the original question about whether to use an optical kill or a choke servo, I think it depends on the plane. On a plane where the choke is hard to reach, I'd probably use a choke servo for the convenience of using it during starting. If the choke is easy to reach by hand, then perhaps an optical kill switch. I usually program my optical kill switches to the spring loaded trainer switch, which works well for me. It's easily accessible if needed quickly, but doesn't tend to get hit accidentally.

-Ed B.