Printout of a story from Aviation Heritage:

The Helicopter Production at Bristol Aeroplane Company

Helicopter design and manufacture had really begun at Bristol when in 1944, following the 'D' Day build up when Raoul Hafner, the Austrian born helicopter designer and his team, who had been working on rotorcraft design, joined the company. They had been employed at the Airborne Forces Experimental Establishment and were effectively made redundant once D Day preparations were complete. Bristol had formed a helicopter department and Hafner and his team were released to form the nucleus of the company design team.

Raoul himself had studied helicopters in Austria and come to England in 1933 and later produced the A.R.III Gyroplane, resembling the Autogiro but having a sensitive cyclic-pitch control instead of the cruder tilting rotor hub as fitted to Juan de la Cierva's Autogiro.

The design phase for the new venture took two years and had originally hoped to use the 500 hp Bristol Aquila but it is possible that the tools and jigs had either been disposed of or more likely lost in one of the many air raids. Of other engines looked at most were untried, or still prototypes, like the Fedden flat six, Roy Feddon having left the company and in business for himself by now, or underpowered. In the event the well tried and proved Pratt and Whitney Wasp Junior of 450 hp was chosen for the first two prototypes. The aircraft was given the type number 171 and was defined in specification E.20/45.

Belvedere over Coventry Cathedral