The Short SB.5 (serial WG768) was a "highly unorthodox, adjustable wing"[1] British research aircraft designed by Short Brothers in response to the UK Air Ministry requirement ER.100; to provide input for the design of the English Electric P.1 (prototype of the English Electric Lightning) by testing the low speed flight characteristics of various configurations of wing-sweep required for supersonic flight.

"[3] The wings were made "of plywood, except for light alloy sheeting at the leading and trailing edges,"[3] which restricted the maximimum speed to a modest 350 knots (403 mph; 649 km/h).

"[3] The flight test report of the SB5 with 60 degrees of sweep and the tailplane in the lower position summarised the design criteria: "At the time of the initial conception of the Short SB5 research aircraft (1949), it was recognised that the trend towards higher angles of sweepback was likely to continue, and this was emphasised by the existence of a design for an operational fighter aircraft, the English Electric P1 (Lightning), which was to have a sweepback of 60°.

The SB5 was designed to allow a gradual approach to this configuration, flying initially with 50° sweepback before conversion to 60° when it would resemble, aerodynamically, a seven-eighths scale model of the Lightning.

Before evaluating the final wing sweep configuration of 69°, a Martin-Baker ejection seat was fitted for the first time and the Rolls-Royce Derwent engine was changed for a Bristol Orpheus of greater thrust.

[2] The first flight, with the final sweep setting of 69° was made by Denis Tayler on 18 October 1960 at RAE Bedford; this was, at the time, the greatest degree of wing-sweep in the world.

In January 1954, the low tail rear fuselage was fitted and tests continued for a further two years and proved that the EEC configuration was correct.