Text in force at CS27-10: from CS27-0, effective 14 Nov 2003.
For each pilot compartment:
(a) The compartment and its equipment must allow each pilot to perform his duties without unreasonable concentration or fatigue;
(b) If there is provision for a second pilot, the rotorcraft must be controllable with equal safety from either pilot seat; and
(c) The vibration and noise characteristics of cockpit appurtenances may not interfere with safe operation.
ED Decision 2003/015/RM · Source