The Fairey Rotodyne.
The Fairey Rotodyne, a compound Gyroplane, was conceived after end of the second world war, when the management at Fairey realised it would need to move into the commercial/military sector rather than being focused purely on military projects. Chosing not to compete directly in the airliner industry, the company took the bold step of developing a helicopter that was capable of ferrying passengers from city centre to city centre without the need of long and expensive runways, and the infrastructure that goes with them, Alongside this it would also be able to function as a military transport capable of hauling up to 8 tonnes internally or slung underneath.
Following the decision to produce a commercial helicopter, Fairey undertook the construction of a "Proof of concept" prototype. The Fairey Gyrodyne FB 1.
This aircraft had the functional performance of a conventional helicopter at low speeds and in the hover, but with the rotor being driven at low torque by the engine and reduced pitch of the main rotor at higher speeds, performed in effect as a gyrocopter, allowing significantly higher speeds than those of same era helicopters. So successful was the prototype that it was chosen in preference to the Westland/Sikorsky Dragonfly and Bristol Sycamore by the British Army for deployment to Malaya. Power was derived from an Alvis Leonides radial engine, fed to both the main rotor and a single tractor propeller mounted at the end of a stub wing. During low speed flight and hovering this small propeller provided the anti-torque thrust needed to counter the main rotor, whilst at higher speeds it provided forward thrust. In 1948, Having achieved a Helicopter world speed record of 124 miles per hour (200 Km/H) the first prototype crashed after a main rotor failure, killing the pilot and observer. Due to delays caused by the crash, in locating and resolving the cause of the crash, the order for 6 Gyrodynes by the M. O. D. was cancelled.
The second prototype FB 1 was subsequently, considerably modified into the Jet Gyrodyne. Changes included replacing the three blade main rotor with a two blade rotor with jets burning a Fuel/air mixture mounted at the tips. The single propeller was replaced with two pusher props, mounted on the stub wings. All of these modifications were carried out in anticipation of the development of the Fairey Rotodyne. Specifically to ascertain the most effective control systems for the project and test the performance of the tip jets, particularly in relighting them for transition from autogyro to helicopter flight. This prototype was retired when the Rotodyne main rotor testing began and can still be seen at the Museum of Berkshire Aviation near Reading in the UK.
(2nd prototype FB 1 modified with twin pusher props and 2 blade jet tipped main rotor.)
After extensive testing, a single demonstrator was built, capable of carrying 40 passengers the Rotodyne first flew in 1957, with the first transition to forward flight in April 1958. Powered by two Napier Eland turboprops mounted under short wings. The tip jets for the main rotors were fed from compressors mounted on the engines both engines in opposing pairs. This meant that if the aircraft suffered an engine failure, power was still available to the main rotor. In fact sufficient power was available, that the Rotodyne could maintain it's hover with one engine shut down and the rotor blades fed by that engine feathered. Also the aircraft could auto-rotate if needed to a safe landing if for some reason the tip jets could not be restarted. Being an autogyro, the aircraft benefited from being able to abort an auto-rotation landing and go around if needed, unlike a conventional helicopter. Over the course of four years the prototype achieved a world speed record of 190.9 mph over 100 km course and flew from London to Paris via Brussels in half the time of a conventional helicopter.
The Rotodyne Tip Jet restart.
Although both commercial and military buyers were interested in procuring the Rotodyne, the project was cancelled in 1962, when funding for the project was withdrawn. Many reasons were cited for the cancellation of this innovative aircraft, and in all probability it was a combination of these. However almost certainly the biggest factors were the British governments insistence on the amalgamation of a vibrant aircraft industry, producing cutting edge designs, into a few large and unwieldy agglomerations that were ill-fitted and rife with internal rivalries, alongside declining interest from both military and commercial sectors. This meant that funding for the project declined. Although noise was reportedly a problem for the Rotodyne with Fairey working on 40 silencer designs by 1955, before the aircraft had even flown, this is not apparent from actual tests flown into London, no complaints about noise being received after several flights. Also the jet tip noise had been reduced from 113 dB. to 96 dB. at 200m less than that of an underground train with further reductions being envisaged.
After 1962, being government property, the aircraft was scrapped and largely destroyed. In a somewhat fitting epitaph for the independent British Aircraft industry, all that remains is the main rotor support, one of the Napier Eland engines, a test rotor blade a few tip jets and a short section of the fuselage, preserved at the Helicopter museum at Yeovil bearing part of the name of a once great aircraft manufacturer Fairey.