LeeL. . whether the "Rules" require it, or not, having a transmitter controlled way to "kill" the engine, in addition to throttle trim shutoff, is just a really good idea. I have only one plane that can't be shut off that way, but the throttle trim on the plane also has to be 4 trim clicks above center in order to run at 1200 rpm, so if I slide the trim all the way back you better believe it's gonna shut down.

That being said, a choke servo is a handy item to have, as it keeps you from reaching near the engine during the startup procedure, and doubles as a "kill" mechanism. Best way to set it up is so that if the engine moves forward it closes the choke. That way, in case of the engine coming loose it will tend to shut down, which is a big help in case of a broken prop blade or motorbox failure. A choke servo only takes a mini-sized servo with a long arm movement, so you can use a 30-35 ounce mini sized servo for choke. Total weight added is about 2 ounces tops, including the linkages, and tied into the LG channel lets you operate it on-off.

One caution. . if you are able to, assign the gear to a switch that is well away from your Rate switches, so that you do not accidentally trip it while switching rates. It's a bad idea to go into 3D maneuvering and try to hit the Rate switch, and then shut the motor off instead. . . Had it happen a couple of times. . I finally assigned it to a push-button instead of a switch, and have never had a problem since.

some things are just a good idea to have on the airplane.. this is one of them.