The Westland Interceptor was a fighter aircraft developed by the British company Westland Aircraft to meet the requirements of Air Ministry Specification F.20/27.
Only one prototype was constructed.
Specification F.20/27 called for a fighter aircraft that could intercept enemy planes during daylight hours.
The primary requirement was that the F.20/27 fighter could overtake an enemy aircraft passing overhead at 150 mph (242 km/hr) and an altitude of 20,000 feet (6,096 meters) in the shortest possible time.
This necessitated a focus on high speed and rate of climb.
Design work on the Interceptor commenced in late 1927, and it made its maiden flight in early 1929, with Lieutnant L. G. Paget at the controls.
The Interceptor was a low-wing monoplane with an all-metal structure and wire-braced wings, covered mostly in fabric, except for the front fuselage. It had a fixed undercarriage.
The single prototype was powered by an uncowled Bristol Mercury IIA, which was later replaced by a Mercury III.
It was equipped with two .303-inch (7.7-mm) Vickers Mk.II machine guns, installed in the sides of the fuselage with the breeches within reach of the pilot.
The guns were synchronized to fire through the propeller and heated to improve their operation at high altitude.
The RAF had intended to call for four-gun armament in Specification F.20/27, but due to an administrative error, it was sent out to manufacturers calling for only two guns.
The handling characteristics of the Interceptor were described as alarming.
In steep turns, the elevator became ineffective, and the aircraft was prone to enter a spiral dive or a spin from such flight attitudes.
The Mercury II engine suffered from persistent high oil temperatures.
Test pilots gave a negative assessment of the Interceptor, causing it to be withdrawn from the F.20/27 competition.
The aircraft continued to fly until 1935, but no orders were placed. Significant aerodynamic modifications were made to improve the handling characteristics, including a considerable increase in the height of the fin and rudder, to improve spin recovery.
The troublesome Mercury engine was exchanged for a Bristol Jupiter VII, and later fitted with a Townend ring to reduce drag.
The Interceptor, along with two other competing F.20/27 designs, the Vickers Jockey and de Havilland DH.77, were historically significant because they were monoplane fighter prototypes, after a long period during which the standard fighter design was a biplane.
However, all three were found lacking in overall performance and handling during the test flights, indicating that the aircraft designers had failed to achieve the project goal.
The F.20/27 competition was won by the Hornet, which entered service under the name Hawker Fury.
Variants
C.O.W. Gun Fighter
The Westland C.O.W. Gun Fighter was an attempt to produce a fighter aircraft armed with a heavy calibre gun.
The Coventry Ordnance Works (COW) 37 mm automatic gun was used, which had been developed for this purpose some years earlier.
The design was in response to Air Ministry specification F.29/27.
The design was an open cockpit single engined metal monoplane with fabric covering.
The aircraft design had already been submitted for specification F.20/27 as the Westland Interceptor but had lost out to the Gloster Gauntlet.
The gun was in the fuselage and fired up at an angle, in order to attack bombers from below.
The plane first flew at the end of 1930, but the trials did not give satisfactory results to continue with the idea.
The COW gun had been developed by 1918 for use in aircraft and had been trialled on the Airco DH.4.
