General Multiple Helicopters Are Losing Tail Control

I flew my TRex 550X a little while ago. At about halfway through my flight, suddenly the heli starts spinning, like the tail servo wasn't working, and I can't control it. It crashed to the ground - not a pretty sight. I thought at the time that maybe the servo wire extension to the tail servo came loose. OK, collected the pieces, patched it up as best I could, paying special attention to the servo wire extension, but I haven't flown it since.

The next week I was flying my TRex 450L - having fun, flying mormally, then the same thing happens. I lose tail control, and it spins to the ground. Luckily it fell on tall weeds so not as much damage this time.

So now I'm left to wonder what the cause was. Both helis have an AR7210BX in them. I thought at first it was the gyro, both recently upgraded to the latest firmware. But it seems unlikely that both would fail in the same way. Now I think it's my radio (a Spektrum DX8 gen 2). But seems like an odd way for a radio to fail - everything going along great, then all of a sudden the tail starts spinning. I haven't had any other issues with any of my equipment.

Obviously I don't think I can fly till I figure this out. I'm considering just chucking my transmitter/gyros and getting new ones, but that's a costly solution (maybe less costly than losing helicopters repeatedly, though).

Anyone else seen this happen? Anyone else have any ideas?

In your Tx, go into the monitor menu and watch the rudder. You will have to set there and play with it for a while, but I would bet you have a bad pot on that stick. Best thing to do if you find a bad pot is to just have them replaced by Spektrum. Sucks that it happened, but it does unfortunately happen.

Had same incident with a Commander Pro for me tail motor burnt-out.

For what ever reason specktrum has terrible luck with pots. It seems to be a common problem with them.

Thanks for the advice. I'll try the monitor test, and follow up with Spektrum.