FAA Federal Aviation Regulations (FARS, 14 CFR)

If there is a device to lock the control system with the rotorcraft on the ground or water, there must be means to --

(a) Automatically disengage the lock when the pilot operates the controls in a normal manner, or limit the operation of the rotorcraft so as to give unmistakable warning to the pilot before takeoff; and

(b) Prevent the lock from engaging in flight.