Originally Posted by Nerobro

So, here's how you do it. You pick up a timer (there all over ebay) You put two metal contacts on the bottom of your car, two metal spring contacts on the trailer bed. Setup a r/c switch, or esc on channel 3 on your car. To trigger the "get down" sequence, you trigger that ESC on you rcar, the signal goes to the bed of the trailer, and it will start the controller.

I'd be looking at a PLC, or an arduino to do the job, but a landing gear retract system might do the job too.

Assuming you have control from the tractor too.. you have a lot of options there.