Not necessarily. The VPX can be set to only allow a run time of three seconds then it will cut off. Due to the nature of my failure, a short in a wire, that was intermittently shorting it managed to run all the way to the stop.
The VPX did eventually, correctly sense an issue and disable the trim. However, and this is what I find most concerning, the trim was mechanically stuck at full deflection.
No amount of switches, or other “interesting” schemes that folks posted on this thread would have prevented this situation.
-Dan
Dan, I'm glad you found the issue and you're safe on the ground. There IS a way to "unstick" the trim at full deflection. We put a lot of thought and testing into the VP-X trim system because of this very failure mode. I'll say with full conviction that it is the safest trim system for exp aviation on the market.
The trim system hardware goes through a self-test every time you boot it up and will flag a fault if something is wrong. Additionally, the hardware has two controllers in series so that if one fails the other will shut down the system. There's more but I digress.
It's important to understand that when on autopilot (and you have auto-trim system) that the autopilot takes over control of the trim system from the VP-X as it is "downstream" of the VP-X.
If I understand correctly, an external wire (prob between the VP-X and the stick) shorted that then commanded the trim to run. If this occurred when the AP was on, nothing would happen because the VP-X was cut out of the control loop by the auto-trim system.
If it happens during manual flight, there are a couple of things built into the system that would have helped:
1. If the trim is running one direction in an uncommanded manner, move the trim switch in the opposite direction and the system will immediately stop the trim motor movement. After a bit (I forgot, I think 2 seconds) if the system sees both up and down trim simultaneously it will then ignore the trim switch inputs for the rest of the flight. The shorted wire will have no further effect. As you mentioned it will also ignore the switch inputs if one is stuck.
2. Go to the EFIS on the VP-X page and select pitch trim. The soft keys will say up and down and you press them to move the trim back to a safe position. The trim only runs while the key is pressed. You can do this at any time, not just when there is an emergency.
More details are in the operating manual.
Again, glad you made it back safely and I hope this helps.