14 C.F.R. § 29.679 Control system locks.
Title 14 - Aeronautics and Space
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.
Title 14: Aeronautics and Space
PART 29—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT
Subpart D—Design and Construction
Control Systems
§ 29.679 Control system locks.