I am looking seriously at the Fuji 43cc EI and have never owned a model with elec. ignition before. Tower mentions the Great Planes cut-off switch should not be used with this engine (strangely, it is in the "recommended accessories" but if you read the description it says it should not be used).

Is there a difference with EI in a kill switch? Won't grounding the circuit stop the spark as in a non-EI gasser?

What should be the set-up for a kill switch?

Thanks much,

I just set up my first gasser... an ExtremeflightRc 74" YAK with a Brillelli 46cc gas engine and CH EI. I used the Smart-fly Optical cutoff switch.

It was very very easy to set up and is cool too, comes with an external red LED to mount on side of plane that tells you when your ignition is armed. Surprisingly inexpensive to boot.

Check http://www.smart-fly.com I recommend it wholeheartedly.

Cheers,

Andrew.

You will find the optical cutoff from smart-fly is the most popular one there is and weighs next to nothing. The one GP sells requires another servo.

Just grounding the plug on most EI's will not work as the plug needs to be grounded by a strap or through the plug cap for the EI to work anyway, but do not hold me to that. I could be way off on that reason

Electronic ignitions (EI) depend on battery voltage, unless powered by a flywheel dynamo. Cutting off the supply, will automatically shut off the spark without any overvoltage surge risk on any component.
Considering this, is is best to put a switch in the primary voltage cirquit, like battery or LT coil. With a coil, it will be wise to place a large capacitor over the switch to "erase" any voltage spikes that may cause switch contact pitting.

The Smart-Fly certainly seems to be the way to go. Thanks for the link Divartix.

I wasn't sure if cutting the EI on a spinning engine would result in no spark or just a poorly timed spark. I guess it's like seperating the points - no spark.

Thanks all. Problem solved.