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Kill switch

jeffw@sc47

jeffw@sc47

Well Known Member
I have heard form casual talk that it is possible to wire in a kill switch to prevent someone from starting the engine (assuming you don't have a keyed ignition switch).

A friend told me that the best (and only way) to do that is to put a 50 or 60 AMP circuit breaker or fuse in the battery circuit to the master solenoid, mount it inside the cowling near the oil filler door.

Is there a low-current circuit anywhere to put an on-off switch that would prevent anyone from starting the engine, or powering-up?
 
I never liked keyed ignition/start switches. I used toggle switches for the ignition and a push button for the starter solenoid. If you place a switch (either keyed or hidden) between the starter button and the starter solenoid, you block someone from being able to crank the engine. The switch only needs to handle the starter solenoid control current.

Carl
 
There are several ways to accomplish your goal. No mater what you do, a knowledgeable person can defeat it. I do not know what a large circuit breaker will do except blow when you try to start the engine. A starter can draw a few hundred amps.
One way to do it is to install a hidden switch in series with the master switch. Or install a hidden momentary push button switch in series with the start contactor coil.
 
I suppose some people can and will steal an airplane, but really not that likely. Steal your avionics? Oh yeah, thats what you need to think about preventing.
 
Who in their right mind is going to steal an Experimental? There is no telling what they are going to get in the way of engine and prop.

They are more than likely to take your electronics.

I wouldn't worry about it. In the 14+ years I have been involved with the RV community, I have yet to hear of someone having their plane stolen.
 
I am with Bill. No need for the switch Jeff in my opinion. I?ve parked to places remote and unguarded, crowded and empty and never had a problem.
 
kill switch

If the goal is to prevent theft, it probably won't help much. If the goal is to prevent kids from doing something silly, might help. My plan is at airshows or places like that to just unbolt the negative wire from my battery.
 
Safety idea

A friend had his amateur built biplane started by a drunken person at a ramp and it got away and almost killed some people, besides being totalled. Rare, but it can happen.

You probably aren't going to stop a determined thief, but you can help to make it a little harder for the casual mistake to happen, meaning someone inadvertently hits the starter button while in the cockpit. Since keyed switches are no longer in vogue (for some good reasons), this has become an even bigger safety hazard, in my opinion.

One thing I do is to run power to the starter button through the strobe/beacon or nav lights switches. Having the strobes on prior to engine start is probably a good idea anyway on some busy ramps. If you think the strobes would be bothersome at night on a ramp, then wire it through the nav lights.

It puts an extra step in the starting process which might be just enough to stop a thief, along with adding an extra safety measure.

Vic
 
Kill it

I built an -8 with a push-to-start button, which has a locked baggage compartment. I installed a guarded kill switch in there, so I could safely leave my unlocked canopy out in public.
 
I don't lock the ignition and I don't lock the canopy. As others have noted, the chances of someone stealing the airplane are minuscule. My fear is that someone intent on stealing avionics would destroy a locked canopy to gain entry. Avionics are insured and easy to replace. A busted canopy may be insured but replacing it is a real pain. I just replaced my cracked canopy so I know what I'm talking about! :mad:
 
jeffw@sc47 said:
Is there a low-current circuit anywhere to put an on-off switch that would prevent anyone from starting the engine, or powering-up?
Click to expand...

Usual approach is bus->breaker or fuse->push-to-start switch->crank solenoid. Insert this instead, and allow the relay to switch the solenoid coil current. Hide the arming toggle in the location of your choice. The flashing LED says the start system is armed. The push-to-start button can be the small, low amp variety...panel mounted, stick grip, whatever.

k50sxg.jpg
 
Keep in mind using any type of arming system that you do not make it so complicated that an inflight restart requires extra steps.
 
A double-pole single-pole switch wired inline with your existing mag switches would let you ground both with a single toggle when needed. That would prevent starting, but not engaging the starter. It would have the safety benefit that when not used as a lockout, it wouldn't affect normal flight operation, in-flight re-start, etc. Just need to place it somewhere it can't be accidentally switched in-flight, like on the instrument sub-panel.
 
jeffw@sc47 said:
the best (and only way) to do that is to
Click to expand...

Definitely more than one way, as you have seen in answers here.

If you want a lower amp solution, a hidden switch or breaker in-line with your master relay is a good way to go. No ignition, no starter, no-anything.

Keep in mind that if you "bump it", you start learning to glide.

A better alternative IMHO is to put a hidden switch in-line with the starter relay. That way if you bump it, you keep flying. You just can't restart it with it off.
 
Preventing startup

I let flocks of youngsters sit in my plane while others fly them around in 4-seaters at our club's annual COPA For Kids event. I remove the somewhat hidden fuses for starter solenoid, fuel pump, and electronic ignition, and manually ground the magneto to avoid catrastophe. Not suggesting you ground your mags, but removing key fuses would stop most thieves and provide peace of mind.
Jay
 
And how do you properly placard a hidden switch?

Why not just use a keyed switch on the panel? I used an industrial grade keyswitch (from McMaster, IIRC) on mine. No key inserted and turned, starter can't be engaged and mags are unable to be ungrounded. Easy peasy.
 
RV7A Flyer said:
And how do you properly placard a hidden switch?

Why not just use a keyed switch on the panel? I used an industrial grade keyswitch (from McMaster, IIRC) on mine. No key inserted and turned, starter can't be engaged and mags are unable to be ungrounded. Easy peasy.
Click to expand...

Ditto. Call it a ?starter enable? switch.
 
Snowflake said:
A double-pole single-pole switch wired inline with your existing mag switches would let you ground both with a single toggle when needed. That would prevent starting, but not engaging the starter. It would have the safety benefit that when not used as a lockout, it wouldn't affect normal flight operation, in-flight re-start, etc. Just need to place it somewhere it can't be accidentally switched in-flight, like on the instrument sub-panel.
Click to expand...

Guessing you might have meant "double pole, single throw" ?
 
DanH said:
Usual approach is bus->breaker or fuse->push-to-start switch->crank solenoid. Insert this instead, and allow the relay to switch the solenoid coil current. Hide the arming toggle in the location of your choice. The flashing LED says the start system is armed. The push-to-start button can be the small, low amp variety...panel mounted, stick grip, whatever.
Click to expand...

Seems a bit more complicated that necessary. I just serial ganged an "arm" toggle switch with a momentary toggle switch and that fires the starter solenoid. With my toggles, if there up, there on.....not sure why youd need a light, but I get thats personal preference of course.
 
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