None needed on a profile.

For that matter, when folks say "arming plug" or "arming switch", do they mean "gizmo that cuts off the timer from the ESC", or do they mean "gizmo that removes battery power from the whole darn system"?

For a while I had an RC plane, where I used a miniature headphone jack for the "on" switch.  "Off" was when the plug was in, "on" was when the plug was out.  I made up a bright red ribbon that said "REMOVE BEFORE FLIGHT" and attached it to the plug -- I thought it looked very decorative sitting on the flight line.  Be kinda heavy if you wanted to cut off battery power, though.

I'd love to see pictures of how people solve this problem with CL planes.

     What? I have 4 e-profiles built over the last 3 years and each one of them has an arming plug and none of them was easy to install but for safety's sake needed. Crist, could you tell me about why I dint need them?  Eric

I simply plug/unplug the battery into the connector attached to the ESC.  What is so hard about that?

     I guess in your case it might be OK. With my planes having hatches to open before you can get to the plug I felt I needed to be able to disarm my planes from the back of the wing away from the motor and perhaps a moving propeller.   Eric

It's more than OK.  It works great and doesn't cost anything extra and it doesn't weigh anything either.

Lets say that if it is hard to get to the battery connection in a hurry an arming plug makes sense.  If the battery plug is readily accessable it acts as the arming plug.  SO I am stating the obvious.

In actual pratice, on a very sleek stunter I am not sure that one would want an arming plug hanging out somewheres.  I am guessing that on these stunters that the battery access hatch goes on easyly.  So once again the battery plug becomes the arming device. My feeling is forget the arming plug.  Plug up the battery at the last minute before the flight. Be careful not to hit the start switch on the timer before you are ready.  AND once the airplane goes hot (battery plugged up) treat it as snake ready to hurt you.  Keep hands out of the prop and keep the airplane pointed away from people and secured until it is time to push your start button and release.

             

   Wow I stuck my finger in the prop - it HURTS!!  

Here's the set up for my E-Impact.  The socket for the arming plug is the female half of the connector which was epoxied into a small piece of 1/8 ply. The external cover is a contoured piece of 1/16 ply.  The Plus lead to the ESC from the battery is interrupted by the connector, so when you insert the arming plug, the ESC is powered.  The arming plug is the male connector with a small piece of brass bar soldered across the terminals and covered with heat shrink. Make the bar wide enough so you can get a grip on it to un-plug easily.

The small toggle interrupts the plus lead from the FM-9 timer to the ESC (that's the small gauge three wire ribbon cable). The white push button is the enable for the FM-9 programmed sequence.

When you are ready to start the flight, the following things occur:

1.  Plug in the arming plug, and the ESC sounds its start up tones. The number of beeps indicates how many cells it sees (Castle ESC).

2.  Flip the toggle to "ON" and the ESC plays its sequence tones (kind of like a bird call, I think)

3.  Push the white button and the propeller spins momentarily, this confirms the timer is talking to the ESC.  You are now walking to the handle as the timer counts down the preset delay (30 seconds, in my case)

The set of switches is set up for a 1-2-3 sequence working forward from the wing.  Flipping the toggle to "OFF" aborts everything, even if the motor has reached flight speed.

Hope this is of help.

John

By all means, do not fly without one. You will save the life of your aircraft, and perhaps a friend.

Here's mine.  I like the nuts and bolts look, because my plane is a take-apart, with 9 visible bolt heads on the airframe.
And the red and black housing and wire, emphasize clean , quiet, efficient, and powerful electric propulsion

There's a sales opportunity here, for someone who either knows of a lightweight switch that can be made to look good, or has the capability to build one.

I'm not sure that a positive cutoff switch is really going to add any more safety to the system than a positive fuel shutoff would.  It seems that you'd do better to put a fuse in of the correct current rating, and have an easy to access 'off' switch on the ESC -- that would protect you from just about any event that a battery cutoff would, except for a severely misbehaving ESC.  Since I haven't heard anything about misbehaving ESCs, this tends to make me think you'd be OK.

Most "batteries in flames" events aren't going to be helped with a cutoff -- once the battery's swelling and smoking, it's just going to go.

I think the idea of an arming plug is for safety of the ground crew and not the airplane.

For that -- assuming that you can trust the ESC -- you just need to cut the timer power.  With no signal to the power a properly functioning ESC isn't going to let the prop turn.

That said, I would never let any body part (mine or someone else's) inside the prop arc at any time when the main battery is plugged in.  So I suppose that extends pretty quickly to needing an arming plug.

Which gets back to needing to make it look good.

Maybe a hatch with a good strong magnet latch over the arming plug?