Armstrong Whitworth Siskin

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Contents

Type Description

• S.R.2 Siskin
• Original Siddeley Deasy prototypes. Single seat, single bay biplane fighter, of wood and fabric construction with parallel interplane struts, initially to meet the requirements of Air Board Specification A1.(a) and later DofR Type 1 and RAF Specification Type I. One 320 h.p. ABC Dragonfly powerplant.
  For Type Description and Specification, see Siddeley Deasy S.R.2 Siskin.

• Siskin Mk.I
• A.W. prototype; original S.R.2 prototype fitted with the 300 h.p. Armstrong Siddeley Jaguar I powerplant.

• Siskin Mk.II
• As Mk.I with a new fuselage of steel tube throughout, externally similar to the Mk.I and braced with tie rods, but retaining the Mk.I wooden wings and parallel chord struts. One each of single and two seat variants built. One 300 h.p. Armstrong Siddeley Jaguar I powerplant.

• Siskin Mk.III
• Mk.II fuselage fitted with fabric covered metal wings and tailplane of new geometry, to Specifications 14/22 & 19/23. The longer span wings featured near square wingtips. The top plane was in two pieces, joined together on the centre-line of the aircraft, carried above the fuselage on four splayed-out struts, with one set of splayed-out V-type interplane struts. Wing construction was all-steel, with fabric covering. The top planes were built up on two spars, each comprising two lengths of rolled steel strip, forming the webs, to which were fitted top and bottom flanges of drawn strip, the assembly being completed by riveting the turned-over edges. The ribs were of Warren-truss type, the top and bottom members being rolled to a circular section, the stiffeners in between being separate pressings of roughly "U" section, riveted to small wrap-plates. There were five cross -braced tubular compression struts in each upper wing. The bottom planes were attached to wing-roots, which were built integral with the fuselage. The bottom planes were built round a single tubular spar, the ribs being of the same construction as in the upper plane . The wing bracing on each side consisted of two interplane lift wires and one interplane landing wire, with an additional lift wire from the undercarriage Vee to the undersurface of the bottom plane. Ailerons were fitted to the top planes only, and tapered from mid span.
  The steel framed tail unit, fabric covered tailplane and fin were built in one unit, the spar and rib construction of the tailplane being similar to that of the top main planes, and featured much reduced fixed fin area below the fuselage and an all new, larger horizontal tailplane, which was now of constant chord and featured variable incidence, the entire tail, including upper fin and rudder, pivoting about the front spar of the tailplane. The elevators were built on a common spar and move as one unit. The rudder was balanced. The undercarriage was of the cross-axle type, the axle being attached to a pair of oleo legs and hinged by two radius rods to a pair of rigidly braced Vees attached to the bottom fuselage longerons, behind and in line with the oleo legs. With only a single spar to the lower wing, the aft leg of the undercarriage vee was now attached to the fuselage underside aft of the wing trailing edge.
  The pilot's cockpit was located under a cutout in trailing-edge of top plane. Armament consisted of two Vickers guns, in the top cowling, firing through the airscrew . Provision is also made for carrying four small fragmentation bombs. One 385 h.p. Armstrong Siddeley Jaguar III powerplant

• Siskin Mk.IIIA
• Mk.III with new, deeper rear fuselage, to Specifications 25/25 & 24/26. The fuselage was a steel tube structure, in two units, divided immediately behind the pilot's cockpit . Each unit was a simple braced structure, comprising four longerons with cross and vertical struts. The rear unit was inclined upwards towards the rudder post, a feature is not noticeable in the complete fuselage, owing to the lines of the top fairing, this being exceptionally deep in the region of the cockpit. With the deeper ffuselage providing more side area, the under-fuselage fin was removed, along with reduced upper wing dihedral. One 385 h.p. Armstrong Siddeley Jaguar IV powerplant.

• Siskin Mk.IIIB
• Mk.IIIA fitted with slotted ailerons and larger fuel tanks, to Specification F.20/27. Initially with Armstrong Siddeley Jaguar IVS, later with 405 h.p. Armstrong Siddeley Jaguar VIII powerplant.

• Siskin Mk.IIIDC
• Two-seat dual control version of Mk.III to Specification 1/28. One 385 h.p. Armstrong Siddeley Jaguar III powerplant.

• Siskin Mk.IV
• Mk.V with short span (25ft) wings: civil racing version.

• Siskin Mk.V
• Similar to the single seat Mk.II, featuring an all wooden wing but of slightly larger span, the lower wing have raked tips similar to the upper. The lower fixed fin was dispensed with and the bottom of the rudder was more rounded. At least G-EBLQ featured the tapered ailerons of the Mk.III. One 385 h.p. Armstrong Siddeley Jaguar III powerplant.

Production Details

Notes

1. Per Thompson and Sturtivant [2], these were J6981 and J6982, returned to Armstrong Whitworth, civil registered on 29 July 1924 with new c/ns and modified for the Kings Cup Air Race of that year. Returned to the RAF in November 1924.
2. J8428 was the second Mk.IIIA to fly, one day after J8048, but was effectively the prototype Mk.IIIA, undergoing all the type testing. Williams [5] states that the Mk.IIIA prototype was most probably built as a private venture and recieved no identification. It was aquired by the Air Ministry in 1926 and, following reconditioning, fitted with experimental wings at Whitley to contract 716958/26 and given the serial J8428. Thompson and Sturtivant [2] point out that that J7001 has been reported elsewhere as being rebuilt as the Mk.IIIA prototype, but the service history of J7001 shows this to be incorrect.
3. Figures per Williams [5]. Tapper [1], other than the two civil registered aircraft plus one tested to destruction, gives only 10 aircraft confirmed as built - Romanian No's 1, 2, 4, 10, 13, 14, 15, 28, 29 and 33. This may imply that those 10 were the only aircraft to be test flown, before all airframes were scrapped.
4. Contract number as given by Thompson and Sturtivant [2], but this is the same contract number they give for reconditioned aircraft.
5. For reconditioned aircraft marked *, Thompson and Sturtivant [2] do not give contract numbers, but the Taken On Charge dates after reconditioning would indicate association with the contracts as shown.

Production References

1. Armstrong Whitworth Aircraft Since 1913, Oliver Tapper (Putnam, 1973)
2. Air Britain RAF Aircraft Register Series J1-J9999 (Air-Britain Publications, 1987)
3. Aerodata Data Plan #3 - Armstrong Whitworth Siskin, Arthur Granger (Vintage Aviation Publications, 1977)
4. Canadian Military Aircraft Serial Numbers at CASPIR (Canadian Aircraft Serials Personnel Information Resource) at the Canadian Warplane Heritage Museum
5. Aeroplane Monthly Feb-Mar 1978.
6. Janes All The Worlds Aircraft 1928, ed. C.G. Grey and Leonard Bridgeman (Sampson Low, 1928)