Armstrong Whitworth Siskin

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Siskin

Role	Fighter
Manufacturer	Sir W.G. Armstrong Whitworth Aircraft Limited
Designed by	F.M. Green
First flight	1919 (Siddeley-Deasy S.R.2 Siskin), 1921
Introduced	1923
Retired	1932
Primary users	Royal Air Force Royal Canadian Air Force
Number built	272

The Armstrong Whitworth Siskin was a British biplane single-seat fighter aircraft of the 1920s produced by Armstrong Whitworth Aircraft. The Siskin was one of the first RAF fighters designed after the First World War; it was noted for its aerobatic qualities.

Design and development

The design was a development of the Siddeley-Deasy S.R.2 Siskin, which was designed by Major F.M. Green (formerly chief engineer of the Royal Aircraft Factory) of the Siddeley-Deasy Motor Car Company, to meet the requirements of RAF Specification Type 1 for a single-seat fighter powered by the promising ABC Dragonfly radial engine. Unfortunately, despite the expectations piled on it, the Dragonfly proved to be a disaster, far less powerful than expected and very unreliable, being prone to overheating and vibration. The Siskin first flew in May 1919, powered by a Dragonfly engine delivering 270 hp (200 kW), far less than the promised 320 hp (240 kW). Despite the engine problems, the Siskin displayed good performance and handling, and it was decided to fit an alternative engine. The engine chosen was the Siddeley Jaguar, the Jaguar-powered Siskin first flying on 20 March 1921.

In 1920, Siddeley-Deasy merged with Armstrong Whitworth, with the aviation interests combined as Armstrong Whitworth Aircraft.

As well as re-engining with the Jaguar, Major Green decided to redesign the Siskin with an all steel structure, as the Siskin III. The Siskin III first flew on 7 May 1923, with first deliveries to the RAF (six for evaluation) taking place in January 1924. The fighter was the first all-metal fighter in the British Royal Air Force.

Following the order from the RAF, Romania ordered 65 aircraft but they were cancelled following a crash on takeoff at Whitley Abbey, Coventry, on 18 February 1925 during acceptance tests; the Romanian pilot being killed.

The main production version was the Siskin IIIA, which originally was powered with a Jaguar IV engine, but was later re-engined with the supercharged Jaguar IVA engine. While the supercharged engine had little effect on performance below 10,000 ft (3,050 m), it greatly improved speed and climb above that height. Following an evaluation of two Siskin IIIs the Royal Canadian Air Force ordered 12 IIIAs which were delivered between 1926 and 1931.

Operational history

RAF Service

A lineup of 29 Squadron Siskins, late 1920s

The first Siskin IIIs were delivered to No. 41 Squadron RAF at RAF Northolt in May 1924, quickly followed by No. 111 Squadron RAF. The Siskin III was popular in service, being an excellent aerobatic platform, although slightly underpowered. The improved Siskin IIIA was first delivered to No. 111 Squadron in September 1926. The Siskin was used by 11 RAF squadrons. The last operational RAF squadron used the Siskin until October 1932 when it was replaced by the Bristol Bulldog.

The Siskin was a superb aerobatic aircraft and presented thrilling exhibitions of flying at every RAF display from 1925 to 1931.

Sweden

The second Siskin III aircraft was sold to the Royal Swedish Air Force in 1925.

Canada

Canada used the aircraft from 1926 until 1939. In 1926, the British Air Ministry sent two Siskin IIIs to Canada for testing by the Royal Canadian Air Force (RCAF) under winter flying conditions. The test pilot was Clennell H. Dickins. The Siskin was considered a modern type when it was introduced into RCAF service, which eventually purchased the Mark IIIA, used to equip the Fighter Flight at Camp Borden and Trenton. In 1937, the Flight became No. I (Fighter) Squadron and was transferred from Trenton to Calgary in August 1938.

Siskin aircraft remained with this unit until the outbreak of the Second World War, eventually to be replaced by Hawker Hurricanes in 1939. The airframes were then turned over to various technical establishments for use as instructional airframes.

Like its RAF counterparts, in 1929, a three-plane Siskin air demonstration team ("The Siskins", Canada's first of its kind) was formed at Camp Borden, Ontario. The aerobatic team put on popular solo and formation displays from coast to coast with one of their most famous manoeuvers involving all three aircraft being tied together by ribbons. At the end of their formation performance, a great show was made that the ribbons remained unbroken.

RAF Armstrong-Whitworth Siskin IIIa from No. 41 Squadron at Northolt being serviced with oxygen.

Air racing

The Siskin was used as a successful racing aircraft, a Siskin V flown by Flight Lieutenant Bernard winning the 1925 Kings Cup Race at a speed of more than 151 mph (243 km/h).

Variants

Siddeley Deasy S.R.2 Siskin - development aircraft (three built)
Siskin II - civil prototype (one built)
Siskin III - all-metal production version (64 built for RAF)
Siskin IIIA - main production variant (Total 348 built, 340 for RAF, eight for RCAF)
Siskin IIIB - prototype with improved engine (one built)
Siskin IIIDC - two-seat dual control version (Total 53 built, 47 for RAF, two for RCAF, two for AST, two for Estonia)
Siskin IV - civil racing version (one built)
Siskin V - civil version for Romania, but used for racing after order was cancelled (two built)