Boulton Paul P.111 - Testing and Evaluation

Testing and Evaluation

The P.111 made its first flight on 10 October 1950, at Royal Aircraft Establishment Boscombe Down with Squadron Leader Bob Smyth at the controls. Later test flying was carried out by the legendary test pilot, Alexander E. "Ben" Gunn, who described the aeroplane as "touchy" and "like flying a razor's edge". Part of the touchiness was because the power controls, essential at high speeds over 450 mph, lacked any feedback. There was also a large trim change when the undercarriage was raised or lowered and landing speeds were high in the absence of airbrakes and because of the need to keep the engine revs up to maintain the generators which powered the control surfaces. In the first few months of flying, the controls were spring-loaded to give a semblance of feel and the rudder was altered to manual control. The P.111 initially had a one piece blown and continuously curved windscreen, but this was replaced by a more conventional framed screen with a flat forward pane.

After a landing accident in which the retractable landing gear failed to extend, the P.111 was modified during its repairs to improve the flight characteristics, and was re-designated the P.111A. Four "petal" airbrakes were added to the fuselage to lower landing speeds and the undercarriage doors were changed to reduce the trim change. A long nose probe carrying a pitot head was added. The most immediately obvious change was the new bright yellow overall paint scheme, the P.111 having been unpainted or silver coloured. The P.111A soon gained the nickname of the "Yellow Peril".

The P.111A first flew on 2 July 1953 from Boscombe Down. Shortly afterwards the anti-spin parachute mounted on the rear port fuselage was strengthened so it could be deployed as a braking parachute and the pilot was given control over the strength of the power controls. It was used by the RAE in a series of explorations of delta wing characteristics and later based at RAE Bedford. During this time it flew with each of the three wing tips.

After a last flight in 1958 it went to the Cranfield College of Aeronautics as a training airframe. In 1975 it was acquired by the Midland Aircraft Preservation Society on long-term loan for its Midland Air Museum at Coventry Airport, making the journey by road on Sunday July 13th, since when it has been on static public display. The P.111 was followed by another delta-winged experimental aircraft, the P.120 which was intended to compare and contrast the behaviour of an otherwise identical tailed delta.