The Westland Whirlwind was a twin-engined cannon fighter used by Great Britain.
The Whirlwind was developed to fulfill the requirement laid out in Specification F.37/35, issued in October 1935. This called for a single seat, single engine, day and night fighter capable of reaching at least 330mph at 15,00ft, with a service ceiling of 30,000ft, maximum take off and landing runs of 1,800ft over a 50ft barrier. and armament of four 20mm auto-cannons. Five of the eight manufacturers invited to tender responded: Boulton Paul and Hawker with single engined designs, Bristol, Supermarine and Westland with twin engined designs, as the words 'single engine' were later deleted from the specification, together with a requirement for the armament to be traversable. Westland submitted it's P.9 design, with estimated prices of £27,000 for one prototype and £45,000 for two, leading to the issuing of contract 556965/36 for two prototypes on 11 February 1937, specifying delivery between August 1938 and February 1939.
The mock up was examined by the Air Staff on 27 April 1937, followed by an RAF inspection on 28 May. The first prototype, L6844, was completed on 27 September 1938, making it's first flight on 11 October 1938,[N 1] before being passed to Farnborough on 1 January 1939, after which the type was cleared for production, with an order for 400 examples to Specification F.37/35/O1/W being submitted on 17 June 1939. [N 2]
The 32nd production example - P6997 - underwent a handling assessment at the A&AEE during April and May 1941, flying with the type's 10 ft leading edge slats both locked and unlocked. The trials indicated that the slats should be permanently locked shut, as there was no difference in handling, and leaving the slats unlocked sometimes resulted in them opening with sufficient violence for them to break away, increasing the risk of structural damage to the wing. From June to August 1941, P6997 took part in a series of day fighter evaluation exercises with the Air Fighting Development Unit at Duxford. During September and October, P6997 - now fitted with a pair of factory installed Mk III universal bomb carriers - was used for low level trials with an external bomb load.
As a result of development problems with the Rolls Royce Peregrine engine, [N 3] the type's entry into service was delayed by almost 20 months,  with the first deliveries taking place in late May/early June 1940, when L6845, P6966 and P6967 were assigned to 25(F) Squadron at North Weald for night-fighter trials. However, doubts regarding the type's suitability for the role led to the Whirlwinds being returned to Yeovil, with 25 Squadron receiving the Beaufighter IF instead.
The first wartime claim for the type was a Junkers Ju 88 'probable', which was intercepted over the Scilly Isles on 12 January 1941, by aircraft from 263 Squadron. This was followed by the first confirmed victory on 8th February, when Pilot Officer Traham was credited with the destruction of an Arado Ar 196, which was presumably spotting for E-Boats.[N 4]
The type had been withdrawn from front line service by 1943. Although the last example was scrapped at Yeovil in 1947, a full-scale replica is being produced by the Whirlwind Fighter Project, based on 3D scans of salvaged components of P6966, the first production example, which crashed at RAF Grangemouth on 7 August 1940, after a tyre burst during take off.
- L6844 made two flights that day - the first from the Westland works at Yeovil, and a second from Boscombe Down.
- In the event only 112 were built, with the order originally being reduced to 200 by the Air Ministry on 26 October, 1938.
- These had been developed from the Rolls Royce Kestrel
- Traham also crashed into the sea, and was killed.
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