Text in force at CS27-10: from CS27-0, effective 14 Nov 2003.
For rotorcraft with wheel-type landing gear, a braking device must be installed that is:
(a) Controllable by the pilot;
(b) Usable during power-off landings; and
(c) Adequate to:
(1) Counteract any normal unbalanced torque when starting or stopping the rotor; and
(2) Hold the rotorcraft parked on a 10° slope on a dry, smooth pavement.
ED Decision 2003/015/RM · Source