Westland Interceptor

Westland Aircraft

Industry	Aerospace
Founded	1915
Headquarters	United Kingdom

Westland Interceptor

The Westland Interceptor was a fighter aircraft created by the British manufacturer Westland Aircraft in response to the Air Ministry Specification F.20/27. During evaluation trials conducted in 1929 and 1930, the aircraft exhibited unsatisfactory flight handling and was ultimately dismissed by the Royal Air Force, which selected the Hawker Fury biplane fighter instead.

Development

Specification F.20/27 outlined requirements for a daylight interceptor fighter. The primary objective was for the aircraft to rapidly overtake an enemy plane flying at 150 mph (240 km/h) at an altitude of 20,000 feet (6,100 metres). This placed a strong focus on achieving high speed and an exceptional climb rate.

Design efforts commenced in late 1927, leading to the Interceptor’s maiden flight in early 1929, piloted by Lieutenant L. G. Paget. The aircraft featured a low-wing monoplane configuration with an all-metal framework and wire-braced wings predominantly covered in fabric, except for the forward fuselage section. It employed a fixed landing gear arrangement. The sole prototype initially used an uncowled Bristol Mercury IIA engine, which was later upgraded to a Mercury III variant. Armament consisted of two .303-inch (7.7-mm) Vickers Mk.II machine guns mounted on either side of the fuselage, with breeches accessible to the pilot. These guns were synchronized to fire through the propeller arc and equipped with heating systems to enhance reliability at high altitudes. Although Specification F.20/27 originally intended for four guns, an administrative error resulted in manufacturers being instructed to equip only two.

Flight testing revealed problematic handling traits described as "alarming." The elevator lost effectiveness during steep turns, and the aircraft frequently entered spiral dives or spins from these conditions. Additionally, the Mercury II engine suffered from persistent overheating issues related to oil temperature. Due to these deficiencies, test pilots provided unfavorable evaluations, leading to the Interceptor’s withdrawal from the F.20/27 contest.

Despite no production orders being placed, the prototype remained operational until 1935. Modifications aimed at improving flight characteristics included substantially enlarging the fin and rudder to enhance spin recovery. The original Mercury engine was replaced first by a Bristol Jupiter VII, later fitted with a Townend ring cowling to decrease aerodynamic drag.

The Westland Interceptor, alongside its competitors—the Vickers Jockey and de Havilland DH.77—held historical significance as monoplane fighter prototypes during an era dominated by biplane designs. However, all three designs fell short in terms of performance and handling during trials, demonstrating that aircraft developers had not yet achieved the intended objectives. Ultimately, the F.20/27 competition was won by the Hawker Fury, which entered RAF service under that designation.

References

Derek N James: "Westland Aircraft Since 1915"