111.—(1) In the circumstances specified in paragraph (2) an aircraft registered in the United Kingdom flying on a public transport flight must carry—
(a)a flight navigator as a member of the flight crew; or
(b)navigational equipment suitable for the route to be flown.
(2) The circumstances referred to in paragraph (1) are that on the route or on any diversion from it, being a route or diversion planned before take-off, the aircraft is intended to be more than 500 nautical miles from the point of take-off measured along the route to be flown.
(3) A flight navigator carried in compliance with paragraph (1) must be carried in addition to any person who is carried in accordance with this Part to perform other duties.