Before revision: Sapphire turbojet engine fitted to an Avro 691 Lancastrian testbed (outer position), June 1954 A testbed aircraft is an aeroplane, helicopter or other kind of aircraft intended for flight research or testing the aircraft concepts or on-board equipment.
After revision: , also referred to as an experimental aircraft,Sapphire turbojet engine fitted to an Avro 691 Lancastrian testbed (outer position), June 1954 A testbed aircraft is an aeroplane, helicopter or other kind of aircraft intended for flight research or testing the aircraft concepts or on-board equipment.