A kill switch should be considered a must with a gas engine. This is the one I use from Electrodynamics. I had the opportunity to need to use it last week when the muffler vibrated off my ZDZ 80. The muffler was hanging by the smoke line. Since there was no back pressure my idle was higher and was not able to be trimmed down low enough to slow the plane. At idle the plane just kept on flying. I had to get it over the runway about six inches high and cut the engine with the kill switch. If it were not for the kill switch I would have had to fly around with no muffler for about 25 min until I ran out of fuel and deadsticked. This is the kill switch I use in all my gassers and it works great.

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