Fairey Gyrodyne / E.4/46 / FB-1
In preparation for the move into rotary-wing development, Fairey had built up a strong helicopter team, led by Dr J. A. J. Bennett, who brought the Gyrodyne proposal to the company in August 1945, and with Sqn Ldr Basil H. Arkell, who joined in January 1946, as test pilot. The first official announcement of the project, a private-venture to specification E.4/46, was made on 3 April, 1946, though no information was then given; at that time the Gyrodyne was known as the FB-1 (Fairey-Bennett One).
Although the broad concept was relatively simple, the translation of this concept into working hardware involved a considerable effort in engineering and other ingenuities. An idea of the amount of 'machinery' in the prototype can be gathered from the fact that nearly 50 per cent of the empty weight was contributed by the powerplant and transmission systems. In these there were four primary units: a 520hp Alvis Leonides nine-cylinder radial engine, with its mounting and systems; a main gearbox with first-stage reduction for the rotor and propeller drives, a clutch and freewheel; an upper gearbox with double epicyclic reduction gear, plus the rotor brake; and a gearbox in the starboard wingtip with the reduction-gear and pitch-changing mechanism for the propeller.
The engine power could be transmitted in variable ratios to a three-blade rotor just over 15m in diameter and to the anti-torque propeller on the starboard tip of the stub wing, the Gyrodyne behaved like a helicopter, but the same propeller also provided the necessary thrust for fast flight, when the aircraft looked almost like an autogyro.
The rotor articulation was designed so that the collective-pitch changed automatically according to the power being applied. The throttle lever was designed to be similar in length, movement and effect to the collective-pitch control of a conventional helicopter and was pulled up to increase power and lift. Fore-and-aft and lateral control was provided by a form of tilting head; although the rotor-hub axis did not physically tilt, as in the case of most autogyros, a similar effect was produced by tilting the rotor head in relation to the axis. Stick-shake was eliminated, using suitable safeguards, by controlling rotor-tilt through irreversible hydraulic jacks.
The Ministry of Supply asked for an alternative rotor-hub arrangement to be designed with overriding collective-pitch and cyclic-pitch blade-angle control so that this could be compared on test with the existing system. This normal helicopter control system was required mainly for trimming purposes at altitude and to provide more positive control when hovering after an autorotative approach.
Yaw control was maintained, as with other helicopters, by altering the pitch of the propeller through conventional pedals. Rudders were fitted for directional control during autorotative flight after power failure. An 'elevator' in the form of a large trim tab, was used to adjust the fuselage attitude when cruising.
A government contract to Specification E.4/46 was awarded for two prototypes, and the first Fairey Gyrodyne, G-AIKF (provisionally serialled VX591), was exhibited almost complete at White Waltham on 7 December 1946.
After 85 engine-running and 56 rotor-testing hours the first untethered flight was made at White Waltham by Basil Arkell on 7 December 1947, weighing just over 2000kg. Testing continued, with longer flights at gradually increasing speeds, until March 1948, when the Gyrodyne was dismantled for examination. By then a second prototype, G-AJJP, had been completed.
The second prototype, basically similar to the first but with more comfortable interior furnishings befitting its role as a passenger demonstrator, was flying by the time of the next SBAC Display, in September 1948, at Farnborough.
Following re-assembly and further tests, G-AIKF was prepared for an attempt on the international helicopter (Class G) speed record in a straight line. This had long been held unofficially by the German Focke Achgelis Fa 61 and more recently a Sikorsky R-5 had also been unofficially timed at 185km/h in the USA. Two eastward and two westward flights over a 3km course at White Waltham were made by Arkell on 28 June, 1948, at an average speed, for the best pair of opposing runs, of 200km/h. In addition to being a world record, this was the first British national record for any helicopter. The course was along the London-Reading railway line on the north side of the aerodrome, and, as it happened, was 45 degrees off a fairly strong wind, so the probability is that a speed of 225km/h might have been achieved in calmer conditions.
Some ten months later an attempt to set up a 100km closed-circuit record ended in tragedy. During trials on 17 April, 1949, two days before the attempt was to be made, the first prototype Gyrodyne suffered a fatigue failure in the rotor head and crashed at Ufton, near Reading, killing F. H. Dixon and his flight observer, Derek Garroway. Dixon, who joined Fairey in 1936 and was chief test pilot from 1942 to 1945, had since been involved in less arduous flying and other duties, but had also shared much of the development and demonstration flying of the Gyrodyne with Basil Arkell.
The investigation following the accident led to a protracted period of investigation and fatigue-testing, and development ceased. The second prototype was grounded and was afterwards very much modified to reappear more than four years later as the Jet Gyrodyne, the test vehicle for the Rotodyne.