Armstrong Whitworth Siskin

The Armstrong Whitworth Siskin was a biplane single-seat fighter aircraft developed and produced by the British aircraft manufacturer Armstrong Whitworth Aircraft. It was also the first all-metal fighter to be operated by the Royal Air Force (RAF), as well as being one of the first new fighters to enter service following the end of the First World War.

Siskin
"The Siskins" flight demonstration team
Role Fighter
Manufacturer Sir W.G. Armstrong Whitworth Aircraft Limited
Designer F.M. Green
First flight May 1919 (as Siddeley-Deasy S.R.2 Siskin), 20 March 1921[1]
Introduction 1923
Retired 1932
Primary users Royal Air Force
Royal Canadian Air Force
Estonian Air Force
Royal Swedish Air Force
Number built 485[2]
Variants Armstrong Whitworth Starling

Development of the Siskin was heavily influenced by RAF Specification Type I, including its initial use of the ABC Dragonfly radial engine. Performing its maiden flight during May 1919, the Siskin proved itself to possess good qualities in spite of the Dragonfly's poor performance. In the following year, a superior engine in the form of Armstrong Siddeley Jaguar was adopted, the first Siskin with this powerplant made its first flight on 20 March 1921. In response to Air Ministry Specification 14/22, the aircraft was redesigned with all-metal construction, and was promptly ordered to meet the specification during 1922.

In May 1924, the first of the RAF's Siskin IIIs were delivered to No. 41 Squadron at RAF Northolt; a total of eleven squadrons would operate the type. Being relatively popular amongst the service's pilots, the aircraft served in excess of eight years before the last of the RAF's Siskins were replaced by the newer Bristol Bulldog during October 1932. In addition to the RAF, various other nations evaluated the Siskin and multiple proceeded to order the type. The Royal Canadian Air Force (RCAF) were one such operator, introducing the type during the late 1920s and continuing to operate its Siskins until shortly after the outbreak of the Second World War. Furthermore, as a consequence of its relatively high performance for the era, several Siskins were entered in various air races.

Development

Background

The Armstrong Whitworth Siskin was a development of the Siddeley-Deasy S.R.2 Siskin designed by Major F. M. Green (formerly chief engineer of the Royal Aircraft Factory) of the Siddeley-Deasy Motor Car Company.[3] A major impetus for the aircraft's development was the Air Ministry's issuing of RAF Specification Type I, which called for a single-seat fighter that was powered by the ABC Dragonfly radial engine. At the time of the specification's release, the Dragonfly had been viewed as a particularly promising powerplant, however, it would prove itself to be incapable of fulfilling its promised performance.[3][4]

The SR.2 Siskin was a single-bay biplane of wood and fabric construction. It possessed a somewhat angular exterior, with seemingly little attention paid to obvious avenues for drag reduction.[5] Perhaps its most distinctive feature was its fixed conventional landing gear, which had relatively lengthy oleo strut shock absorbers carrying the axle, which was in turn connected by radius rods to a pair of V-struts situated behind the axle. Its wings were of unequal span. It was powered by a single ABC Dragonfly radial engine, which was installed on the nose of the aircraft within a streamlined cowling to reduce drag; to regulate the temperature of the engine, each individual cylinder had its own cooling channels. Armaments consisted of a pair of Vickers machine guns which were mounted in the nose decking in front of the pilot.[1][6]

During May 1919, the Siskin conducted its maiden flight.[6] While the initial aircraft was powered by the intended Dragonfly engine, it was only capable of delivering 270 hp (200 kW) rather than the promised 320 hp (240 kW).[1] In spite of its early promise, the Dragonfly proved to be somewhat disastrous, being not only far less powerful than expected and but also suffering from a low level of reliability, being prone to overheating and catastrophic levels of vibration that would frequently result in crankshaft failure after only a few hours of use.[7] Irrespective of the engine, the Siskin itself displayed several good properties, possessing favourable stability and handling characteristics, along with performance that could outmatch several of its contemporaries.[8][6]

Redesign

In 1919, Siddeley-Deasy merged with Armstrong Whitworth, with the aviation interests becoming Armstrong Whitworth Aircraft.[9] Siddeley-Deasy had inherited the design of the RAF.8 fourteen-cylinder radial engine and its designer Sam D. Heron. By 1920, this engine, which had become known as the Jaguar, had been developed sufficiently to be a possible replacement for the Dragonfly.[10][6] One of the prototype Siskins was outfitted with a Jaguar and made its first flight in this configuration on 20 March 1921.[1] Its performance impressed Air Ministry officials, who urged Armstrong Whitworth to continue developing the aircraft, as well as indicated that only an all-metal design would be acceptable if the type was to be acquired by the Royal Air Force (RAF).[11]

During 1922, Air Ministry Specification 14/22 was issued, seeking an all-metal single-seat high performance landplane. Armstrong Whitworth submitted the Siskin as its response, which led to an order for a single Jaguar-powered prototype being placed.[12] As well as re-engining with the Jaguar, Major Green redesigned the aircraft to include an all-metal structure, as the Siskin III. The change from wood to metal construction was a requirement of the Air Ministry's war production plan, which intended to make use of Britain's extensive motor car industry for aircraft production, something which would not viewed as possible for aircraft composed of wood. The all-metal Siskin was the start of a general transition to metal for military aircraft, which enabled a rapid increase in aircraft production when required to meet wartime demand.[13][14]

Into production

On 13 October 1922, an initial contract for three production aircraft was placed, a follow-on order for a further six followed on 26 January 1923; this second order including one that was configured as a prototype of a two-seat variant.[15] The Siskin III, the first version with an all-metal frame, performed its first flight on 7 May 1923, piloted by Frank Courtney.[16][5] It was subject to a comprehensive evaluation, during which the ailerons were tapered to prevent reoccurrence of a jam that happened during one test flight. Shortly thereafter, Armstrong Whitworth commenced construction of the production standard Siskin, the first of which was delivered to the Royal Air Force (RAF) during January 1924.[16] The fighter was the first all-metal aircraft to be procured in quantity for the RAF.[17]

Following the initial order from the RAF, Armstrong Whitworth quickly embarked on an intense marketing effort aimed at securing export sales for the Siskin. The aviation author Oliver Tapper credited the aircraft and its sales as having played a major role in the company's fortunes for a time.[18] At one point, Romania placed an order for 65 aircraft, but these were all cancelled amid acceptance tests on account of a fatal accident at Whitley Abbey, Coventry; on 18 February 1925, one aircraft crashed while attempting to take off, resulting in the death of its Romanian pilot.[19] However, Tapper alleges that political pressure exerted by France over Romania was the real cause for the order's cancellation.[20]

The principal production version was the Siskin IIIA, which was first ordered during 1926.[21] This variant was originally was powered with a Jaguar IV engine, but was later re-engined with the supercharged Jaguar IVA engine instead. According to the aviation author Francis K. Mason, this supercharger, which was a relatively novel innovation at the time, had relatively little effect on performance when the aircraft was flown below 10,000 ft (3,050 m), but it greatly improved both speed and climb performance when it was flown above that height.[19] Following an evaluation of two Siskin IIIs, the Royal Canadian Air Force ordered 12 IIIAs, which were delivered between 1926 and 1931.

While early production was handled inhouse by Armstrong Whitworth, this did not remain the case throughout the Siskin's production run.[22] Due to the company's attention and resources both being heavily engaged by the production of the Armstrong Whitworth Atlas, it was decided to subcontract the production of a number of later-built Siskin IIIAs to other aircraft companies, resulting in this variant being built by Blackburn Aircraft, Bristol Aeroplane Company, Gloster Aircraft Company, and Vickers.[23]

Operational history

Royal Air Force
A lineup of 29 Squadron Siskins, late 1920s.

During May 1924, the RAF's first Siskin IIIs were delivered to No. 41 Squadron at RAF Northolt.[16] Shortly thereafter, No. 111 Squadron also received the model; its adoption enabled No. 111 to become the RAF's first high-altitude fighter squadron.[24] The Siskin III was relatively popular amongst its pilots, being a highly manoeuvrable aircraft, although slightly underpowered. Between 1925 and 1931, Siskins were frequently presented at RAF exhibitions of flying; one particular feat performed was the linking of three aircraft by cords between their interplane struts, necessitating careful formation flying to not break these cords until the finishing manoeuvre was performed.[25]

During September 1926, the first deliveries of the improved Siskin IIIA variant were made to No. 111 Squadron.[26][27] In total, the Siskin was operated by eleven RAF squadrons. By 1931, the type was showing its age, leading to the Air Ministry considering either to recondition them or to procure new-built fighters to replace them.[28] During October 1932, the final Siskins in RAF service were withdrawn, the type having been replaced by the newer and more capable Bristol Bulldog.[26]

Sweden

The second Siskin II aircraft was sold to the Royal Swedish Air Force in 1925.[29] It was equipped with skis and flown in an experimental capacity for a time.[30]

Canada
RCAF Siskin IIIDC, c. 1937 (PAC Photo).

Between 1926 and 1939, Canada operated a sizable fleet of Siskins. During 1926, the British Air Ministry had dispatched a pair of Siskin IIIs to Canada, where they underwent testing by the Royal Canadian Air Force (RCAF) under winter flying conditions by test pilot Clennell H. Dickins.[31] The Siskin was considered a modern type at the time of its acquisition by the RCAF, which opted to purchase the Mark IIIA. The Canadian procurement involved both new-built aircraft and second-hand RAF Siskins being supplied to numerous RCAF squadrons.[31]

The Siskin equipped the Fighter Flight at Camp Borden and Trenton. During 1937, the Flight became No. I (Fighter) Squadron, and was transferred from Trenton to Calgary in August 1938.[32] RCAF Siskins were also frequently used in aerial displays and long distance tours around North America.[33]

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

The unit continued to operated the Siskin up until the outbreak of the Second World War, shortly after which the type was rapidly retired and replaced by Hawker Hurricane monoplane fighters.[32] Following the Siskin's withdrawal by the RCAF, the airframes were turned over to various technical establishments for use as instructional airframes.

Like its RAF counterparts, in 1929, a three-plane Siskin air demonstration team was formed at Camp Borden, Ontario – the RCAF's first official flight demonstration team.[34] The aerobatic team put on popular solo and formation displays from coast to coast.[35]

Air racing

The Siskin frequently participated in air racing, often triumphing in such events. Multiple examples were entered into the 1924 Kings Cup Race, one of which achieving the fastest course time despite arriving fourth.[36] In the 1925 King's Cup Race, a Siskin V flown by Flight Lieutenant Barnard emerged as the winner, having reportedly achieved a speed in excess of 151 mph (243 km/h).[37]

Variants
  • Siddeley Deasy S.R.2 Siskin – Prototype fighter aircraft built by Siddeley-Deasy and powered by Dragonfly engine. Three built.[6]
  • Siskin II – fabric covered steel-tube fuselage and wooden wings. Two built, one two-seater and one single-seater.[38]
  • Siskin III – all-metal production version (64 built for RAF[39])
  • Siskin IIIA – main production variant ordered in 1926[21] (Total 348 built, 340 for RAF, eight for RCAF[39])
  • Siskin IIIB – prototype with improved engine. Single example converted from Siskin IIIA.[40]
  • Siskin IIIDC – two-seat dual control version (Total 53 built, 47 for RAF, two for RCAF, two for AST, two for Estonia[39]) a further 32 were converted from Siskin IIIs.
  • Siskin IV – civil racing version (one built[39])
  • Siskin V – single-seat fighter for Romania. 65 ordered and at least 10 completed before order cancelled. Two used for racing.[41]

Operators

Military operators
 Canada
 Estonia
 Sweden
 United Kingdom

Civil operators
 United Kingdom
  • Air Service Training Limited

Specifications (Siskin IIIA)

Data from The British Fighter since 1912[43]

General characteristics

  • Crew: 1
  • Length: 25 ft 4 in (7.72 m)
  • Wingspan: 33 ft 2 in (10.11 m)
  • Height: 10 ft 2 in (3.10 m)
  • Wing area: 293 sq ft (27.2 m2)
  • Empty weight: 2,061 lb (935 kg)
  • Max takeoff weight: 3,012 lb (1,366 kg)
  • Powerplant: 1 × Armstrong Siddeley Jaguar IV 14-cylinder air-cooled radial piston engine, 385 hp (287 kW) [44]
  • Propellers: 2-bladed fixed-pitch propeller

Performance

  • Maximum speed: 156 mph (251 km/h, 136 kn) at sea level
  • Range: 280 mi (450 km, 240 nmi) [45]
  • Endurance: One hour and twelve minutes
  • Service ceiling: 27,000 ft (8,200 m)
  • Rate of climb: 2,953 ft/min (15.00 m/s)
  • Time to altitude: ,10,000 ft (3,048 m) in seven minutes and five seconds

Armament

  • Guns: Two × 0.303 in (7.7 mm) Vickers machine guns
  • Bombs: Provision for up to four × 20 lb (9 kg) bombs under-wing

See also

Aircraft of comparable role, configuration, and era

Related lists

References

Citations
  1. Mason 1992, p. 149.
  2. Tapper 1988, p. 140.
  3. Mason 1992, p. 148.
  4. Tapper 1988, p. 117.
  5. Tapper 1988, p. 123.
  6. Tapper 1988, p. 118.
  7. Gunston 1986, pp. 8–9.
  8. Lumsden 1991, p. 74.
  9. Tapper 1988, p. 18.
  10. Lumsden 1991, pp. 73–74.
  11. Tapper 1988, pp. 118-119.
  12. Meekcoms and Morgan 1994, p. 51.
  13. Ritchie, Sebastian. Industry and Air Power The Expansion of British Aircraft Production 1935-1941. Routledge Taylor and Francis Group, 1997. ISBN 0-7146-4343-2, pp. 25-26.
  14. Tapper 1988, pp. 119-121.
  15. Meekcoms and Morgan 1994, p. 66.
  16. Mason 1992, p. 164.
  17. Tapper 1988, p. 141.
  18. Tapper 1988, pp. 17-18.
  19. Mason 1992, p. 165.
  20. Tapper 1988, p. 128.
  21. Moss, Roger. "Armstrong Whitworth Siskin". British Aviation – Projects to Production. Archived from the original on 12 August 2011. Retrieved 4 May 2011.
  22. Tapper 1988, p. 124.
  23. Tapper 1988, pp. 140–141.
  24. Tapper 1988, p. 129.
  25. Tapper 1988, p. 132.
  26. Donald 1997, p. 64.
  27. Tapper 1988, p. 131.
  28. Tapper 1988, pp. 133-134.
  29. Jackson 1973, p. 45.
  30. Tapper 1988, p. 122.
  31. Tapper 1988, p. 135.
  32. Tapper 1988, pp. 136.
  33. Tapper 1988, pp. 135-136.
  34. Millberry 1984, p. 45.
  35. Dempsey 2002, pp. 25–41.
  36. Tapper 1988, pp. 124-126.
  37. Jackson 1972, p. 57.
  38. Tapper 1988, pp. 121–122.
  39. Tapper 1988, p. 371.
  40. Tapper 1988, pp. 369, 371.
  41. Tapper 1988, pp. 126–128.
  42. Thetford 1991, pp. 143–144.
  43. Mason 1992, p. 166.
  44. Tapper 1988, p. 142.
  45. Angelucci 1981, p. 118.

Bibliography
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  • Dempsey, Daniel V. A Tradition of Excellence: Canada's Airshow Team Heritage. Victoria, BC: High Flight Enterprises, 2002. ISBN 0-9687817-0-5.
  • Donald, David (ed.). The Encyclopedia of World Aircraft. London: Aerospace Publishing, 1997. ISBN 1-85605-375-X.
  • Gunston, Bill. World Encyclopaedia of Aero Engines. Book Club Associates, 1986.
  • Jackson, A.J. British Civil Aircraft since 1919, Volume 1. London: Putnam, 2nd Edition,1973. ISBN 0-370-10006-9.
  • Lumsden, Alec. "On Silver Wings — Part 5". Aeroplane Monthly, February 1991, Vol 19 No 2, Issue 214. pp. 72–78. ISSN 0143-7240.
  • Mason, Francis K. The British Fighter Since 1912. Annapolis, Maryland: Naval Institute Press, 1992. ISBN 1-55750-082-7
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  • Milberry, Larry. Aviation in Canada. Toronto: McGraw-Hill Ryerson Limited, 1979. ISBN 0-07-082778-8.
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