14 C.F.R. § 29.1151 Rotor brake controls.
Title 14 - Aeronautics and Space
(a) It must be impossible to apply the rotor brake inadvertently in flight. (b) There must be means to warn the crew if the rotor brake has not been completely released before takeoff.
Title 14: Aeronautics and Space
PART 29—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT
Subpart E—Powerplant
Powerplant Controls and Accessories
§ 29.1151 Rotor brake controls.