Keylock switch

I need some edumacation here. I did some research, and some things that I thought of as "must have" seem to be optional. So in short, it seems a question to the experts is in order.

Background: VP-X and Dual EFII.

The existing plan was this:
My ignitions are wired through a DPDT keylock switch, rated at 10a @ 12v on each pole.
My starter is wired per the VP-X diagram on page 24, with my switch being a momentary rocker.

If I understand this correctly, that means that if the VP-X is energized (i.e. the Master is on), and the start switch is pressed, the prop will swing even if the keylock is in the off position. Granted, the engine can't start without ignition, but that still seems dangerous.

Is that a normal or acceptable practice? I saw in several posts were people are skipping a keylock all together. I am not worried about the plane being stolen, so much as I am worried about an "always hot prop".

What I really want to avoid is somebody later asking "Why the heck did you wire it that way?"

We need to talk about only one circuit at a time, the starter circuit. Regardless of how the starter is wired, the prop is not always hot. In other words, turning the prop by hand will not cause the engine to start no matter how the starter contactor is wired (as long as the ignition is off). What is dangerous is if one person is standing near the prop and someone else inside of the cockpit turns on the master and pushes the start button. Yes, some planes are wired that way. If you want to eliminate that danger in your plane, then use a momentary key switch for the starter contactor instead of a push button.

There are a lot of ways to do this. I am not a fan of the old spam can ignition switch after some experience with them failing.

What I also worry about is some kid getting in the plane and hitting the "start" button. Even with the ignition off the starter swinging the prop is not a good thing.

What I do:
- Each ignion has a locking DPDT toggle switch. One side of the switch controls the ignition. The other side provides power to a piezo buzzer. The ground for the buzzer is provided by the alternator "ALT" light. This way if the ignition is on and the engine is not running, you hear the buzzer. If the engine is running, there is no ground for the buzzer so it is silent. Stepping out of you plane and hearing the buzzer is the "I left the mags hot" warning.
- The starter is controlled with a standard momentary push button.
- I have added a hidden toggle switch in line with the starter push button. Parking on the ramp the switch is open. I'd guess someone would eventually find the hidden switch - but it would take a lot longer than just jumping around a key switch. This is what I added to keep a kid from climbing in and cranking the engine.

This is a dirt simple approach. You can add a VPX to the mix if you want, but would do no more that what I discribed.

Carl

Chuck,
Did you use the EFII Bus Manager? No "pro or con" but it changes the way things work.

rvsxer said:

Chuck,
Did you use the EFII Bus Manager? No "pro or con" but it changes the way things work.

Click to expand...

No I did not. But to simply my question, it really comes down to this:

Option 1: Master requires no key, Start will spin prop if Master is on. Ignition requires a key.

Option 2: Master requires a key, Ignition will be hot anytime Master is on.

Any other Option would require a second keylock, which I would rather not do.

It seems to me that Option 2 is far more dangerous, so Option 1 might be my best bet. Mostly I wanted to make sure it was a) Legal, and b) Not the only one like that.

Option 3

Start switch requires a key. This will preclude the "kid in the cockpit" from energizing the starter. Master and ignition can be unkeyed.

Cheers, David
RV-6A A&P

koupster said:

Start switch requires a key. This will preclude the "kid in the cockpit" from energizing the starter. Master and ignition can be unkeyed.

Cheers, David
RV-6A A&P

Click to expand...

Kid can now switch on (un ground) the mags and have a HOT prop.

A hidden DPDT switch can ground the mags a second time and disable the starter button.

Another option is to use two momentary start push button switches in series, one switch on the instrument panel and one under the panel. Locate the two switches so that you can press the panel mounted switch with your thumb and the hidden switch with a finger on the same hand. Kids or unauthorized people (barefoot bandit) are unlikely to press both switches at once.

gasman said:

Kid can now switch on (un ground) the mags and have a HOT prop.

Click to expand...

Reminder, this is an EFII system, so No Mags. Without the keylock ignition, the prop can spin, but there is no ignition.

A hidden switch is an idea, but the concept doesn't appeal too much to me, not being a fan of hidden things.

BTW, a kid in the cockpit will NOT happen. I have a canopy lock, and will use it always. Any kids approaching unattended will be met by the hounds from ****. Attended and in the back seat is fine. Unattended in the front isn't going to happen. Let's just say that isn't "part of my mission".

Do kids or other people just open a canopy and start pushing buttons? There is no key required on my setup, do I need to lock the canopy if I leave it anywhere besides the hangar?

There are other ways to wire a keyswitch...on mine, the keyswitch ON is required before a) the starter switch (pushbutton) will work, AND b) the mags can be ungrounded (more specifically, the L mag, which is the one with the impulse coupling).

No key inserted and the keyswitch OFF? Prop can't be spun by starter, turning prop by hand can't cause the impulse coupled-mag to fire.

No need for "hidden switches" (which I find kinda kludgy), or multiple switches, or what have you.

Oh, and yes, it's "safe" in that if the keyswitch blew apart in flight, the engine would still run on the R mag.

400+ trouble-free hours (but you need to get a good, reliable DPDT keyswitch).

Do kids or other people just open a canopy and start pushing buttons? There is no key required on my setup, do I need to lock the canopy if I leave it anywhere besides the hangar?

Click to expand...

Have you seen the horror stories on here about what kids AND grown people have been caught doing to airplanes at fly-ins and such?

3PDT would be needed

RV7A Flyer said:

There are other ways to wire a keyswitch

Click to expand...

The wiring is simple, but in my situation in order to do that (which I would very much prefer), I would need a 3PDT keylock switch. I have been unable to locate any that are rated for at least 10a @ 12v. I have tried Aviation websites, Digikey, Mouser, OnlineComponents, Element14, and several dozen more obscure sites. If anyone is aware of a source, please let me know.

cdeerinck said:

The wiring is simple, but in my situation in order to do that (which I would very much prefer), I would need a 3PDT keylock switch. I have been unable to locate any that are rated for at least 10a @ 12v. I have tried Aviation websites, Digikey, Mouser, OnlineComponents, Element14, and several dozen more obscure sites. If anyone is aware of a source, please let me know.

Click to expand...

You just need a relay, that's all.

Doh!

RV7A Flyer said:

You just need a relay, that's all.

Click to expand...

Doh! Ok, relay on order. No clue why I didn't think of that. Sometimes, not only can I not see the forest for the trees, but I seem to be rooting around under a bush. Thank you!

Everyone has their preferred approach, and none of the ones I've seen suggested here strike me as "wrong". But I thought I'd share my solution to this particular problem just to provide another data point.

I have two DPDT switches with pull-style guards for the mags. I have a simple SPST keyed switch for the master. I have a guarded pushbutton for the start. The mag switches are wired such that one side controls the mag ground, as you'd expect. The other side is wired such that the starter button is energized ONLY if the Left mag is ON, and the Right mag is OFF. Yes, this means I start on a single mag ... and that is the one downside of this arrangement. That said, I've had no starting problems associated with using one mag.

Once started, the right mag goes ON and from that point the start button is de-energized. This has been so effective in avoiding having people accidentally crank the engine that I've had an A&P call me saying there was something wrong, he couldn't get the engine to crank, and I had to explain the switch setup.

The final benefit of this arrangement is that if I have my key in my pocket ... the master is OFF. If I don't have my key, I screwed up.

DwightFrye said:

Everyone has their preferred approach, and none of the ones I've seen suggested here strike me as "wrong". But I thought I'd share my solution to this particular problem just to provide another data point.

I have two DPDT switches with pull-style guards for the mags. I have a simple SPST keyed switch for the master. I have a guarded pushbutton for the start. The mag switches are wired such that one side controls the mag ground, as you'd expect. The other side is wired such that the starter button is energized ONLY if the Left mag is ON, and the Right mag is OFF. Yes, this means I start on a single mag ... and that is the one downside of this arrangement. That said, I've had no starting problems associated with using one mag.

Once started, the right mag goes ON and from that point the start button is de-energized. This has been so effective in avoiding having people accidentally crank the engine that I've had an A&P call me saying there was something wrong, he couldn't get the engine to crank, and I had to explain the switch setup.

The final benefit of this arrangement is that if I have my key in my pocket ... the master is OFF. If I don't have my key, I screwed up.

Click to expand...

Seems like the only shortcoming here is that you lose the ability to turn the Master on but prevent accidental starts...i.e., Master on, but starter cannot be engaged under any circumstances.

I found having the ability to turn the Master on, while the mags cannot be ungrounded and the starter cannot be engaged unless the key is in and on, very useful while working on avionics, etc., in the hangar. I can put the aircraft on ground power, turn the Master on, and work away, all with the engine completely safe...