I just recieved a BCMA 26 for my first gas engine. Would it be O.K. to use a regular battery switch in between the battery and the ignition module to use for the kill switch? I don't understand the need for a specifically made "gas engine kill switch" to arm/disarm the ignition. This engine will be going on a G.P Super Stearman and I was thinking about mounting the kill switch in the forward cockpit for easy and safe access. All you pros out there help! I have sunk a nice chunk of cash on this bird and I don't want to ruin it with an improper setup! Thanks!

Well if you have a choke on it then you would be fine with the switch but other wise the gas engine is different than glow because the glow will shutdown if you close the throttle all the way where as the gas engine will keep running till it runs out of fuel so if you are flying with glow you can hit the throttle kill if you set it up and also that glow engine will be out of fuel in about 15 minutes. The gas engine on the other hand will run for 30 minutes or so on a tank so if you have no way of shutting down well you will be flying along time till you run out !!!

Huh? I thought the question was if he had to use a specially made gas engine kill switch or if he could use a regular switch disconnecting the ignition battery. I'd like to know too as I am also new to gas engines.

I would think a normal switch mounted away from the receiver so that it would not cause interference would work fine. I would question if there would be enough separation mounting the kill switch in the cockpit.

John

There is a lot of good info out to explain this ignition switch deal....start at http://www.wildharerc.com/downloads/...%20engines.pdf ,
Tom has put a great "getting started" article in there that is accurate and can be trusted.

First, however, the reason to locate the ignition switch forward is that usually forward moves the switch and it's leads further away from the Receiver and it's wiring. Important to try and keep 12" minimums if you are using non-PCM 72Mhz radios. If using 2.4, doesn't matter so much. (Not supposed to matter at all, and that's been my experience running Spektrum/JR stuff). Ignition wiring produces electrical "noise", which 72Mhz FM can pick up and start twitching controls.

Second, a "remote Kill switch" is strongly advised for several reasons, but not because the gasser won't quit when the throttle butterfly plate is closed. A properly-adjusted gasser WILL die when the throttle plate closes completely. If it does not, there is a problem with that engine carburetor or it's adjustments. However - throttle servos in gassers get more exposure to vibrations transmitted to the gear train. This can create undue failure of the gear train, the servo mounting, or electronics failure of the throttle servo. So, the "fix" is to use some device that disconnects the electrical power from the module. Most use a specially-designed electronic switch that plugs into an extra channel in the RX so the radio link from the TX can kill the engine, regardless of the throttle servo or linkage condition. Strongly recommended my many.

Third, to answer your original question - any good quality "standard" radio-type switch can be used on a gasser with a modern module. Since you'll use a rechargeable ignition battery, probably a good idea to consider the charging jack/wiring of the switch to make your install easier. Most use HD switches with integrated charging jacks.

Thanks for the information and the link Bob.
John

Anytime!
Good luck.

So from reading the link.

I could use a servo to operate the choke instead of a using remote operated kill switch. But in either case a remote controlled shut off is advisable. Whether it is a slide switch controlled by a servo, choke controlled by a servo or a new special opto isolated ignition kill switch. The opto controlled switch having the advantage of less possible ignition interference because it is easier to maintain a 12" separation from the receiver.

Next, use a heavy duty switch harness so I can manually turn off the power to the ignition and have a port to charge the ignition battery.

Then try to keep everything electronic 12 inches away from the ignition and use no metal to metal linkages.

Got it.
Thanks,
John

EXACTLY, John!!!!!
(I have a strong bias for the electro-optical kill switch. Servo-operated choke floods the cylinder if used too frequently, and can foul plugs, makes hard starting, etc. But - it does work, and I used that method for a few years.)

In that case I'll use the opto isolated switch. After all it's only money. Plus it will be a lot easier to craft than a servo controlled switch.
John

In that case, I'll make my personal choice (I have 3 of these).... http://www.42-percent-products.com/gas-accessories.htm
Excellent product, High quality, great value!

Thanks for the link. Looks like a good product.

My buddy is building a 1/3 scale BUSA cub. He is powering it with a Zenoha 62 and planning on using a servo controlled kill switch. I notice they also have a magneto kill switch. It will save him some time. I'm going to send him the same link.

John

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I have used all 3 methods, throttle adjusted to help kill the engine, choke servo to activate the choke, and a fiber optic kill switch. I believe if I remember correctly AMA states must be able to kill engine via TX.
All 3 of these methods have worked for me in the past, HOWEVER I have since went with the Fiber Optic due to safety reasons, as with Smart-Fly (which is what I use) monitors the RX and will shut ignition off if there is interference that would result in control loss. I came to this after watching a 35% bird go in at full throttle and was extremely luck it was not in the middle of folks!!!!

Good point and if (I know this has never happened to anyone ) you break an engine mount and find the throttle no longer is palying nice you can stop the thing before it rekits itself if you on your toes that is

IMAA is the group that requires the remote kill.

It is ALWAYS good to be able to stop these things....I've known folks that rigged a spring loaded pinch device on the fuel line. There are many ways skin the cat.... I wish everyone agreed that a remote "kill" of some kind **WAS** required...