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British twin-engine, high altitude heavy fighter
The appearance over England during September 1942 of the very high-flying Junkers Ju 86P, although not entirely unexpected, caused considerable consternation in Fighter Command, for these pressurised reconnaissance bombers were to all intents and purposes beyond interception. In fact, the Junkers aircraft were to prove operationally ineffective and would soon be withdrawn by the Luftwaffe, but this was not known by the RAF at the time, and urgent action had to be taken to try to find an antidote to the raiders. The fact that Fighter Command had no high-altitude fighter available to counter the Ju 86P in 1942 did not result from any official oversight. The need for such a fighter had already been recognised and work was under way on such type, while the whole field of pressure cabin development was receiving special attention. However, the progress of the war in 1940-42 had required that greater priority be given to other aspects of fighter development and production, and the new high-altitude interceptor was still well over a year from entering service when the Luftwaffe mounted its first tentative high altitude sorties over Britain.
The planned counter-weapon was the Westland Welkin, the prototype of which still had not flown when the Ju 86Ps made their operational debut.
On 9 January 1941, Westland was authorised by the Ministry of Aircraft Production to proceed with two prototypes of its P.14 design for a twin-engined high-altitude fighter, in compliance with Specification F.4/40. Conceived as a two-seater with six 20-mm cannon armament, the P.14 went ahead as a four-cannon single-seater with a pressurized cockpit. Revised to conform to F.7/41, and thus competing with the Vickers Type 432, the P.14, to be named the Welkin, first flew on 1 November 1942. The wing was located in the mid position, and power was provided by two Rolls-Royce Merlin Mk 61s of 1,565 hp, these being succeeded by 1,650 hp Merlin 72/73 or Merlin 76/77 in the production Welkin I. Pressurization of the cockpit was achieved by means of a Rotol blower on the starboard engine. Production of the Welkin I was initiated in 1941, contracts for 100 and then 200 being placed, and the first series aircraft was under test at Boscombe Down by mid- September 1943. However, handling problems combined with reduced operational interest in high-altitude fighters led to cancellation of production after the completion of 75 (1 converted to the Mk.II), 2 prototypes plus 26 airframes without engines. The Welkin Mk I saw no service use.
During 1943, Westland studied a number of possible derivatives of the Mk I in order to take advantage of the design work already completed. Of these possibilities, one for a two-seat night fighter variant received a go-ahead on 4 February 1943, subsequent development of this as the Welkin NF Mk II being in accordance with Specification F.9/43. Two prototypes were ordered, as conversions of Mk I airframes during production, and orders were given for 60 of the final production batch of Mk Is to be to this standard. As flown on 23 October 1944, the prototype Welkin NF Mk II introduced AI Mk VIII radar in a lengthened bulbous nose and a new one- piece canopy over a two-seat cockpit in which the observer faced aft behind the pilot. Production plans for the Welkin NF Mk II were cancelled during 1945, along with those for the F Mk I, and the second prototype was not completed.

Type

• Single-seat high-altitude fighter.

Wings

• Mid-wing cantilever monoplane.
• Wide center section extending beyond the engine nacelles with outer wings set at a greater dihedral.
• All-metal, single-spar, stressed-skin structure.
• Flaps on the center section.
• Ailerons on the outer sections.

Fuselage

• Oval section structure in two parts:
  • Forward section: cabin made of duralumin, stressed for pressurization, and bullet-resistant.
  • Rear section: made of magnesium, monocoque with longitudinal planking.
• Cabin bolted to the front face of the main wing spar, terminating with a steel armored bulkhead.

Tail Unit

• Cantilever monoplane type.
• Tailplane mounted about one-third up the fin for good anti-spin qualities at high altitudes.
• Rudder in two portions, separated by a torpedo-shaped fillet forming the intersection of the tailplane and fin.
• Electrically-operated trim tabs in elevators and rudder.

Landing Gear

• Retractable type.
• Main wheels retract backward into engine nacelles.
• Tail-wheel retracts into the fuselage.
• Features Lockheed shock absorbers, Dowty hydraulic retraction, and Dunlop wheels and brakes.

Power Plant

• Two Rolls-Royce Merlin engines with two-speed, two-stage superchargers:
  • Mk. 72 or 76 in the starboard nacelle.
  • Mk. 73 or 77 in the port nacelle, driving the Rotol cabin supercharger.
• Rotol four-blade constant-speed, full-feathering propellers.
• Coolant and oil radiators in the center section between the fuselage and nacelles.
  • Air led to radiators by a ducted leading-edge entry.
  • Variable exit at the trailing edge controlled by the angular setting of the main landing flaps.
• Integral and armored fuel tanks in the center section, outboard of the nacelles.

Accommodation

• Pilot’s cockpit in line with the leading edge of the wing.
• Pressurized cockpit with a Westland control valve automatically regulating cabin pressure.
• Automatic cabin heating control maintains a stable temperature at all heights, eliminating the need for special clothing.
• At low altitudes, either heated or cold air can be admitted as desired.
• Pressure-resistant cockpit canopy and bullet-proof windscreen, double-skinned with a space for warm air circulation by pump to prevent icing and misting.

Armament

• Four 20 mm British Hispano cannons in the fuselage nose.

Dimensions

• Span: 70 ft. (21.35 m)
• Length: 41 ft. 6 in. (12.6 m)
• Height: 15 ft. 9 in. (4.8 m)
• Wing area: 460 sq. ft. (42.7 sq. m)

Weight (Loaded)

• 17,500 lbs. (7,945 kg)

Performance

• Maximum speed at operational height: 385 mph (616 km/h)
• Range: about 1,500 miles (2,400 km)

Serials:

Prototypes: DG558/G and DG562/G
block: DX278-DX420
Possibly block: HS680-HT521
PF370 Mk II
WE997

Source:

Westland Welkin F Mk.I, NF Mk.II – 4+publications
RAF Fighters Part 3 – William Green And Gordon Swanborough
Westland Aircraft since 1915 – Derek N James
The Complete Book of Fighters An Illustrated Encyclopedia of Every Fighter Aircraft Built and Flown – William Green, Gordon Swanborough