How many different types of engine did the Vulcan's first prototype fly with?

The Vulcan was designed for the Bristol Olympus, but when the first prototype, VX770, was ready, that engine was not yet available. Rather than wait, the aircraft first flew on 30 August 1952, flown solo by Roly Falk, fitted with four Rolls-Royce Avon RA.3 engines producing 6,500 lbf (29 kN) of thrust each. That first prototype, painted glossy white and featuring its pure delta wing, carried only the first pilot's ejection seat.

In January 1953 VX770 was withdrawn from flying to have fuel tanks fitted in the wings, along with other systems and Armstrong Siddeley Sapphire ASSa.6 engines rated at 7,500 lbf (33 kN). It flew again in July 1953. Meanwhile, the second prototype, VX777, had already flown with the Olympus 100 engines of 10,000 lbf (44 kN) that the first prototype never got to carry.

In 1957 the Sapphires gave way to four Rolls-Royce Conway RCo.7 engines of 15,000 lbf (67 kN), and the aircraft passed to Rolls-Royce as a testbed for the Conway, regarded as the world's first turbofan. It flew with them until its fatal crash at a flying display at RAF Syerston in September 1958. German Wikipedia dates the crash to 14 September 1958.

VX770's career started a tradition: throughout its life, several Vulcans served as engine testbeds, among them the Conway, Spey, and the Olympus 593 used on Concorde.

The aircraft originated from Specification B.35/46 issued by the British Ministry of Supply. Deliveries of the much-improved Vulcan B.2 began in 1960, and the last example reached the RAF in January 1965.