Vulcan Bomber
Design and development
Design work began at A. V. Roe in 1947 under Roy Chadwick. The Air Ministry specification B.35/46 required a bomber with a top speed of 500 knots (930 km/h), an operating ceiling of 50,000 ft (15,000 m), a range of 3,000 nautical miles (5,500 km) and a bomb load of 10,000 lb (4,500 kg); intended to carry out delivery of Britain's nuclear armed gravity bombs to strategic targets within Soviet territory (east of the Ural mountains). Design work also began at Vickers and Handley Page. All three designs were approved — aircraft that would become the Valiant, the Victor, and the Avro Vulcan.
The Type 698 as first envisaged was a delta wing tailless, almost flying wing design, as Avro felt this would be able to give the required combination of large wing area, sweepback to offset the transonic effects and a thick wing root to embed the engines; these were staggered in the wing with two forward and below and two back and above. Wingtip rudders gave the control. There were two bomb bays, one in each wing. This design was reworked in light of Ministry comments and became more conventional adopting a centre fuselage with four paired engines and a tail.
The prototype Vulcans (VX777 front, VX770 rear) with four Avro 707s at Farnborough in September 1953 showing the initial straight wing leading edges.
As the delta wing was an unknown quantity Avro began scale prototype testing in 1948 with the single-seater Type 707 aircraft, and despite the crash of the first prototype on 30 September 1949 work continued. The first full-scale prototype Type 698 made its maiden flight (after its designer was killed in an unrelated aircrash) piloted by Roly Falk on 30 August 1952, [1] shortly before appearing at the SBAC Farnborough Airshow. Since the Bristol Olympus (mod 01) engines were not ready the aircraft was launched with the Rolls-Royce Avon. These would be replaced with Armstrong Siddeley Sapphires as well, before the Olympus were ready. The Vulcan name was not chosen until 1953 after the Valiant had already been named.
The two prototypes initially flew with a straight leading edge that was subsequently modified to have a kink further out towards the wingtip. The Vulcan bomber in service was not fitted with pure delta wings; but the prototypes models were the first jet bomber design to use a wing of that shape, which was modified in development to give the service machines better flying characteristics than a pure delta could supply.
Testing the vehicle was relatively crude in those days; for example, recording the instrument readings involved filming the control panel and manually transcribing the results onto graph paper. As well, testing the brakes of the Vulcan included strapping the company photographer Paul Culerne to the front landing gear with the aircraft moving at full landing speed and photographing the brakes in operation. [2]
Despite its large size, it had a relatively small radar cross-section (RCS). It is now known that it had a fortuitously stealthy shape apart from the tail fin.
Avro test pilot Wing Commander (retired), Roly Falk, demonstrated the aircraft's high performance in the second production Vulcan, XA890, by performing an upward barrel-roll immediately after takeoff at the 1955 Farnborough Airshow. [3] The roll was performed while gently climbing so that positive g is maintained and stresses reduced.
The Vulcan was normally operated with a crew of five - two pilots, two navigators and an Air Electronics Operator (AEO), with the AEO responsible for all electrical equipment in a role similar to that of flight engineer on earlier propeller aircraft. Only the pilot and co-pilot were provided with ejection seats. The fact that the "rear crew" were not provided ejection seats has been the basis of significant criticism; there were several instances of the pilot and co-pilot ejecting in an emergency and the "rear crew" being killed because there was not time for them to bail out.
The navigator plotter (navigator), navigator radar (bombardier) and AEO (electronic warfare officer) bailed out through the crew entrance door in the cockpit floor immediately ahead of the nose wheel, their parachutes opening automatically by static line. As the crew door was immediately forward of the front undercarriage, it was very important that bail-out was only attempted with the undercarriage retracted. The method of escape was practiced regularly in ground rigs, and successfully used on more than one occasion, with all crewmembers surviving.
The Vulcan used entirely powered control surfaces, this combined with the relatively small space for the flight crew meant that a fighter-like stick could be used instead of a control column with the added benefit that ejection could be quicker in an emergency. Power was 100 volts DC electrical supplied from generators on each engine. Backup was from a set of batteries in series to supply the voltage if generators failed. These had little capacity in event of a power loss so the system was revised for the Mark 2 to use a Ram Air Turbine (RAT) that would operate at higher altitude and an Airborne Auxiliary Power Unit (AAPU) which could be started once the aircraft had reached a lower altitude – 30,000 ft (9,100 m) or less. At the same time the power system was changed to 200 volts at 400 Hz AC from constant frequency generators.
With no view to the rear from the cockpit and with the control surfaces (four elevators and four ailerons in the Mark 1, elevons for the Mark 2) at the extreme rear of the aircraft there was a display board on the pilots control panel that showed the position of all eight so that any non-responding surface could be identified. The AEO also had a periscope that gave a view to the rear so that the bomb bay and the underside could be checked.