Crew members at station
42.—(1)  For every flight mentioned in regulation 3(1)(a) or (b), the pilot-in-command must ensure that —
(a)every person assigned duty on the flight as a crew member who is on duty during take‑off, landing or such other time as the pilot‑in‑command directs, is at the crew member’s station with the safety belt, or harness where so equipped, fastened unless the person’s absence is necessary for the performance of duties in connection with the operation of the aircraft; or
(b)every person assigned duty on the flight as a flight crew member who is required to be on flight deck duty remains at the flight crew member’s station with the safety belt fastened unless the person’s absence is necessary for the performance of duties in connection with the operation of the aircraft or out of physiological need.
(2)  A person assigned duty as a crew member for a flight mentioned in regulation 3(1)(a) or (b) must not perform any activity during a critical phase of flight unless the activity is required for the safe operation of the aircraft.