Bristol Belvedere The Bristol Type 192 Belvedere was a British twin - engine , tandem rotor military helicopter built by the Bristol Aeroplane Company . It was designed for a variety of transport roles including troop transport , supply dropping and casualty evacuation . It was operated by the Royal Air Force ( RAF ) from 1961 to 1969 . Design and development . The Belvedere was based on the Bristol Type 173 10 - seat ( later 16 - seat ) civil helicopter which first flew on 3 January 1952 . The 173 project was cancelled in 1956 and Bristol spent time on the Type 191 and Type 193 to Royal Navy and Royal Canadian Navy specifications . These two naval variants were cancelled , but the RAF expressed an interest in the aircraft and the Type 192 " Belvedere " was created . Three Type 191 airframes were almost complete when the order was cancelled , but they were used to aid the development of the Type 192 . The first two were used as test rigs for the new Napier Gazelle engines and the third was used for fatigue tests . The Type 192 shared some of its design features with the cancelled naval variants , which made it less than ideal for transporting troops . The front undercarriage was unusually tall , originally designed to give adequate clearance for loading torpedoes underneath the fuselage in the anti - submarine warfare role . This left the main passenger and cargo door above the ground . The engines were placed at either end of the cabin , precluding the possibility of a rear access ramp , which might have been present in a purpose - designed troop transport ( such as the contemporary Boeing CH - 47 Chinook ) . To provide access to the cabin from the cockpit there was a small gangway past the engine that resulted in a bulge on the port side of the fuselage . The first Type 192 prototype " XG447 " flew on 5 July 1958 with tandem wooden rotor blades , a completely manual control system and a castored , fixed quadricycle undercarriage . From the fifth prototype , the rotors fitted were all - metal , 4 bladed units . Production model controls and instruments allowed night operations . The prototype machines had an upwards - hinged main passenger door , which was prone to being slammed shut by the downwash from the rotors . This was replaced by a sliding door on the later aircraft . 26 Belvederes were built entering service as the Belvedere HC Mark 1 . The Belvederes were originally designed for use with the Royal Navy but were later adapted to carry 18 fully equipped troops with a total load capacity of 6 , 000 lb ( 2 , 700 kg ) . The two rotors were synchronised to prevent blade collision through a shaft , allowing the aircraft to operate through only one engine in the event of an emergency . Bristol attempted to market a civil variant of the helicopter , designated the Type 192C . The 192C would have had seats for 24 passengers and was aimed at intercity services . To demonstrate the aircraft ' s potential , Bristol chief test pilot Charles " Sox " Hosegood set the London – Paris and Paris – London speed records in May 1961 in a Belvedere . However , no orders were placed for the 192C . Operational history . The first prototype Belvedere went to the Belvedere Trials Unit at RAF Odiham , which was subsequently reformed as No . 66 Squadron RAF in 1961 . Engine starter problems caused trouble early on but operational deployment continued . The prototype saw service in Europe , Africa , Southern Arabia and Borneo . " XG447 " was broken up at Boscombe Down on 7 August 1966 . In June 1960 the 5th prototype , " XG452 " set a speed record of between Gatwick and Tripoli . In 1962 another Belvedere lowered the spire onto the new Coventry Cathedral . As well as 66 Squadron , the type was deployed to 72 Squadron in 1961 and 26 Squadron in 1962 all at RAF Odiham . 26 Squadron later transferred to RAF Khormaksar where it disbanded in November 1965 . The helicopters were transferred by HMS " Albion " to Singapore to join 66 Squadron until the squadron was disbanded in 1969 . 72 Squadron kept its Belvederes until August 1964 when it exchanged them for Westland Wessex . The RAF Belvederes were involved in combat in Aden Emergency and Borneo ( during the Indonesia – Malaysia confrontation ) . Its capability of transporting 18 fully armed troops or freight was really appreciated by the British Army . Aircraft on display . The following Bristol Belvederes have been preserved and are either on display or currently undergoing restoration .