Text in force at 29-59: from 29-0, effective 1 Feb 1965.
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.
29 FR 16150 · Source