The Avro 707, was the first British aircraft with a delta-wing – a research aircraft to prove the concept of delta wings for the 3 times as large Avro Vulcan that was to follow.
The first Type 707 aircraft (serial VX784) made its maiden flight on 4 September 1949 at Boscombe Down. Tragically, test pilot Eric Esler lost control of the aircraft at low speed on 31st September and fatally crashed near Blackbushe.
The loss of the first prototype resulted in work on the second Type 707 aircraft being suspended for a time, until a number of modifications were introduced to save time and simplify the construction. The long pointed nose section intended for the Type 707A was grafted onto the fuselage, resulting in the new aircraft being 12 ft (3.66 m) longer than the original. Redesignated Type 707B (serial VX790), the maiden flight took place at Boscombe Down on 5 September 1950.
Flight testing of the 707B from Dunsfold soon justified Avro’s faith in the delta wing and its relatively docile handling characteristics. In February 1951, the ‘inverted-w’ bifurcated dorsal air intake had been replaced by more efficient and more elegant single intake with a NACA venturi inlet, and by August 1951 an ejection seat had been installed and a revised cockpit canopy fitted. Primarily designed for flight testing in the 80-350 knots speed range, the aircraft nevertheless quickly ran into problems with canopy turbulence causing starvation of the dorsal engine intake and it was resolved to abandon this feature on the forthcoming Type 707A.
The contribution of the Type 707B to the Type 698 programme was rather limited because a good deal of time was spent on modifications which were relevant only to the 707B itself – principally attempts to cure pitch instability. It did however assist in defining the relatively high ground-incidence angle which a delta wing required for take-off. On 21 September 1951 VX790 was damaged in a landing accident and returned to Woodford for repair. Upon returning to Boscombe Down it took up general research duties with the Royal Aircraft Establishment (RAE) and Empire Test Pilots School (ETPS), until badly damaged in another landing accident at Farnborough on 25 September 1956 in the hands of an ETPS student. The aircraft was judged to be not worth repairing and subsequently used for spares for the remaining 707A and 707C aircraft. It was dumped at RAE Bedford in 1960.
For various reasons, the early Avro 707s took too long to reach the flight test stage, and consequently their direct contribution to the Type 698 Vulcan programme was comparatively small. However, the Avro 707 family of research aircraft gave British aircraft designers early confidence in the general handling characteristics of the delta-wing, which lead to its adoption on other aircraft types (several of which where cancelled in 1957), and some of the systems tested found a direct application on other military aircraft programmes.