O.Tapper Armstrong Whitworth Aircraft since 1913 (Putnam)

The Siskins

   The most significant aircraft to be designed and built by the Siddeley Deasy company was the S.R.2, a single-seat fighter which, in its developed form, was to become famous in the RAF. Originally it had been intended that the S.R.2 should be powered by the proposed 300 hp fourteen-cylinder two-row radial engine which, as the RAF 8, was being designed under Major Green at Farnborough but was passed over to Siddeley Deasy when Green joined the company in 1917. In the event, the development of the radial engine was deferred so that priority could be given to bringing the Puma engine up to production standard. Thus it was that the Siddeley S.R.2, afterwards to be named the Siskin, was first flown with the ill-fated A.B.C. Dragonfly nine-cylinder radial engine.
   It was natural that a fighter designed by John Lloyd under the direction of Green should bear a resemblance to the S.E. series built under Green's leadership at Farnborough and, in fact, the Siskin's S.E. parentage was clearly evident. It has been suggested that the design which emerged as the Siskin had already been roughed out by Green before he left Farnborough, but both he and Lloyd have denied that this was so: nevertheless, it seems likely that, but for the change in Government policy towards Farnborough, the aeroplane that became the Siskin might very well have been the S.E.7.
   Whatever may be the truth of its origin, the Siskin was a very good aeroplane and, together with the engine which later became the Jaguar, it was responsible for the initial success of the Armstrong Whitworth company - although it was still some way into the future when the first Siskin made its maiden flight from Coventry's Radford aerodrome in the spring of 1919. It was an elegant biplane with wings of unequal span and chord and a spidery-looking undercarriage with long-stroke oleo shock-absorbers, a feature that became familiar on all subsequent Siskin variants. The Dragonfly engine was neatly installed in a well-streamlined cowling with individual cooling channels for each cylinder and blending into a spinner on the propeller boss.
   On test in the summer of 1919, the Siskin was found to have excellent handling and stability characteristics. Its performance, too, was generally superior to most of its Dragonfly-powered contemporaries. An Air Ministry test report records that the S.R.2 attained a speed of 145 mph at 6,500 ft and climbed to 10,000 ft in just under eight minutes.
   The original order for the Siddeley Deasy fighter was placed sometime early in 1918 and was for six aircraft, but later in the year the order was cut to three, by which time the first of the S.R.2 airframes was partially completed. By this time, too, it had become clear that the 300 hp radial would not be forthcoming in time and, as explained above, it was decided to substitute the A.B.C. Dragonfly engine. Even then, a shortage of Dragonfly engines held up the completion of the three aircraft-which bore the serial numbers C4541, C4542 and C4543 - and although the first airframe was probably completed some time in the latter half of 1918, the first flight does not appear to have taken place until early in 1919. With the failure of the Dragonfly engine in 1919, the Siskin passed into eclipse and, apart from a brief appearance at the RAF Pageant at Hendon in June 1920, little was heard of it until C4541 reappeared in March 1921, now fitted with the new Armstrong Siddeley Jaguar radial engine and bearing the family name of Armstrong Whitworth in place of Siddeley Deasy.
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P.Lewis The British Fighter since 1912 (Putnam)

During this time, one of the most important of the new British singleseat fighters of the early post-War era was being developed at its prototype stage. Prior to Maj. F. M. Green’s departure in 1917 from the Royal Aircraft Factory to design for the aviation section of the Siddeley-Deasy Motor Car Co. at Coventry, he prepared the preliminary layout for another fighter in the Factory’s Scouting Experimental series, based on the installation of a two-row fourteen-cylinder radial engine - the 300 h.p. R.A.F.8. Once Maj. Green, J. Lloyd and S. D. Heron had settled down to work at the Siddeley-Deasy offices, the design was developed in earnest to emerge as a sprightly-looking biplane, the Siddeley S.R.2 Siskin, in mid-1919. At the same time, at Maj. Green’s instigation the Company had gone ahead with the development of the R.A.F.8 engine and completed it as the Jaguar.
   The Siskin flew first in July, 1919, with the unfortunate choice of the 320 h.p. A.B.C. Dragonfly 1 as its power plant, but this was eventually replaced by the Jaguar which had been turned into a reliable and successful unit by the Summer of 1922. The prototype Siskin followed the usual all-wood construction and fabric covering of the war period and carried the standard pair of Vickers guns on its nose-decking as armament. The Siskin was not ordered at the time but much was to be heard of it later in its revised and developed version.

F.Mason The British Fighter since 1912 (Putnam)

Siddeley S.R.2 Siskin

   The following two aircraft, the Siddeley Siskin and the Nieuport Nighthawk, were the only aircraft, originally powered by the infamous ABC Dragonfly radial engine, to occupy a significant place in the history of British aviation, even though the original aircraft subsequently underwent a fair degree of alteration by foster parent companies.
   The Siddeley-Deasy Motor Car Company of Coventry, apart from undertaking the manufacture of other companies’ designs during the First World War, began to build aircraft of inhouse design during 1917, after Maj F M Green, J Lloyd and S D Heron (formerly of the Royal Aircraft Factory) joined the firm in senior design appointments. After designing a modified version of the R.E.8 (taken from the production line and re-designated the R.T.1, but which was not put into production), Maj Green began detailed work on a design which he had sketched out while still at Farnborough, where he had intended using the 300hp RAF 8 fourteen-cylinder two-row radial engine, then under early development.
   However, by the time the new aircraft design had begun to take shape early in 1918, aircraft designers were becoming enamoured with the potential offered by the ABC Dragonfly single-row radial which was claimed to possess an exceptionally good power/weight ratio. Green accordingly adopted this engine and tendered his design to Air Board Specification A.1A (which became RAF Specification Type I in April 1918). Based on the promised power/weight ratio of 0.53 bhp/lb, the aircraft was expected to achieve a top sea level speed of around 160 mph. In the event the Dragonfly never exceeded a figure of more than 0.445 bhp/lb. Nevertheless, Siddeley-Deasy received a contract in May to produce six prototypes, C4541-C4546. Owing to delayed delivery of the first engine cleared for flight, the first Siskin to fly (the third prototype, C4543) was not taken aloft until May 1919, and even then the engine was developing no more than about 270 hp.
   The S.R.2 Siskin (named in accordance with TDI 506A and 538) was an attractive aeroplane, displaying much of the S.E.5’s character, though with interesting new features, not least of which was the undercarriage; this comprised single oleo struts for each wheel, each end of the axle being attached to the apices of paired V-struts by radius struts. The engine cowling was also novel, with each cylinder aligned to lie in a fluted channel in the crankcase cowling, this arrangement being intended to ensure the best possible cooling air flow through the cylinder fins. Like the S.E.5 and other Factory aircraft, the Siskin possessed tail fins above and below the rear fuselage. Despite the disappointing engine power, the Siskin returned a maximum speed of 145 mph at 6,500 feet when C4543 visited Martlesham Heath in July 1919.
   By March 1920 the first five Siskin prototypes had flown, all with Dragonfly engines, even though it had already been decided to seek an alternative engine. Such an engine was near at hand. This was a development of the RAF 8 fourteen-cylinder engine referred to above. On leaving the Factory to join Siddeley-Deasy, S D Heron had sought and gained permission to continue its design development in his new appointment. Considerable progress was made before differences of opinion arose over cylinder design and Heron left the company to take up a design appointment in America. His departure resulted in a run-down in effort on the new engine, now named the Jaguar, until S M Viale took over the design late in 1919. By mid-1920 the engine was bench running and showing some promise, and an early Jaguar I, rated at 325 hp, was flown in the first Siskin prototype, C4541, on 20 March 1921.
   By then a much improved version of the aircraft, the Armstrong Whitworth Siskin III had been ordered in prototype form and a whole new chapter in the Siskin’s life was about to open.


   Type: Single-engine, single-seat, single-bay biplane fighter.
   Manufacturer: The Siddeley-Deasy Motor Car Co Ltd, Coventry.
   Specification: Air Board Specification A.1A (later RAF Type I).
   Powerplant: One 320hp ABC Dragonfly I; later 325hp Siddeley Jaguar I.
   Structure: Fabric and ply covered wooden box-girder construction.
   Dimensions: Span, 27ft 6in; length, 21ft 3in; height, 9ft 9in; wing area, 247 sq ft.
   Weights: Tare, 1,463lb; all-up, 2,181lb.
   Performance: Max speed, 145 mph at 6,500ft; climb to 10,000ft, 7 min 50 sec; service ceiling, 23,800ft.
   Armament: Two synchronized 0.303in Vickers machine guns on upper nose decking.
   Prototypes: Six ordered, C4541-C4546 (first flight, May 1919, by C4543). No confirmation can be traced that C4546 was completed.

W.Green, G.Swanborough The Complete Book of Fighters

SIDDELEY S.R.2. SISKIN UK

   When, in January 1917, Capt F M Green became chief aeronautical engineer of the Siddeley-Deasy Motor Car Company, he began the design of a single-seat fighter, the S.R.2. A compact single-bay sesquiplane predominantly of wooden construction with fabric skinning, the S.R.2 was powered by a 320 hp A.B.C. Dragonfly nine-cylinder radial engine. Armament comprised two synchronised 0.303-in (7,7-mm) machine guns. A contract for six prototypes was reduced to three in mid 1918, the first of these flying in April 1919, by which time the fighter had been officially named Siskin. The first prototype Siskin was subsequently re-engined with an Armstrong Siddeley Jaguar, development in this form continuing after Siddeley Deasy acquired in 1921 the name and goodwill of Sir W G Armstrong Whitworth & Co Ltd, and the Armstrong Whitworth Siskin II emerging in 1922.

Max speed, 145 mph (233 km/h) at 6,500 ft (1980 m).
Time to 6,500 ft (1980 m), 4.5 min.
Service ceiling, 23,800 ft (7255 m).
Empty weight, 1,463 lb (664 kg).
Loaded weight, 2,181 lb (989 kg).
Span, 27 ft 6 in (8,38 m).
Length, 21ft 3 in (6,48 m).
Height, 9 ft 9 in (2,97 m).
Wing area, 247 sqft (22,95 m2).

J.Bruce British Aeroplanes 1914-1918 (Putnam)

Siddeley S.R.2, the Siskin

  IT would be almost true to say that the Siskin missed being the S.E.7 only because of the recommendations of the Burbidge Committee. The first rough outlines were sketched by Major F. M. Green shortly before he left the Royal Aircraft Factory to join the Siddeley-Deasy company. The original concept envisaged the use of the 300 h.p. R.A.F. 8 engine, a fourteen-cylinder two-row radial which was designed in September, 1916.
  However, the real design work was done at the Siddeley-Deasy works, and it could fairly be claimed that the Siskin was the first all-Siddeley design. In common with such contemporaries as the Ara, Basilisk, Nighthawk, Snapper and Snark, the Siskin was not completed until 1919: it appeared in the summer of that year and underwent its official trials in July. Like those single-seaters, too, the Siskin was powered by the 320 h.p. A.B.C. Dragonfly I radial engine.
In the Siskin great care was taken to make the engine installation as clean as possible; a blunt spinner was fitted, and the engine cowling blended harmoniously with it. The airframe was predominantly a wooden structure. The basic fuselage box-girder had faired sides as far back as the cockpit and a rounded top-decking throughout its length. The pilot sat fairly high. The mainplanes were of unequal span and chord, and were characterised by centre-section bracing reminiscent of that of the Sopwith 1 1/2-Strutter, outwards-raked interplane struts, and raked tips. The tail-unit was of characteristic shape, yet embodied features that were to be seen in the S.E.5, R.E.8, and R.E.9, and also bore a certain resemblance to that of the Austin Greyhound. The undercarriage was of distinctive design: shock absorption was by means of the main single oleo legs, the lower ends of which were linked by radius-rods to the apices of a pair of vee-struts a short way aft.
  The Siskin did not go into production in its original form, doubtless because of its Dragonfly engine. Yet with that engine it had a better performance than most of its contemporaries, and was one of the sweetest-natured of aeroplanes. It flew at the R.A.F. Pageant in 1920, when it was obliged to bring off a hurried forced-landing because of engine failure.
  In view of its war-time origin, it is not without interest to trace the history of the Siskin’s later power unit, the Armstrong Siddeley Jaguar engine.
  As related above, a fourteen-cylinder radial engine of 1,374 cu in. displacement was designed at the Royal Aircraft Factory in September, 1916. The new engine design was named R.A.F. 8 but was not built at Farnborough.
  When Major F. M. Green joined the Siddeley-Deasy Motor Car Co., Ltd., early in 1917, his immediate responsibility was the development of the 230 h.p. B.H.P. engine. He asked for and obtained permission to develop the R.A.F. 8 engine, and put S. D. Heron in charge of the design work.
  On April 5th, 1917, the Air Board issued a specification for a new aircraft engine. The specification, known as Scheme A, had been inspired by the Admiralty, and called for a radial engine of not more than 42 inches diameter capable of developing at least 300 h.p. This specification might have been that of the R.A.F. 8 itself, and J. D. Siddeley submitted the design to the Air Board. The engine which won an official contract was the Cosmos Mercury; nevertheless, Siddeley continued the development of the R.A.F. 8, and the name Jaguar was given to the new engine.
  Cylinder design was by S. D. Heron, and the engine was the first to have an all-aluminium head with two valves inclined at a large angle to each other; this design feature was to be found in radial engines several decades later. J. D. Siddeley ordered the construction of the cylinders to be made similar to that of the Puma but when, in the middle of 1917, he instructed Heron to fit a new cylinder head with three valves, Heron resigned rather than do so.
  Thereafter Jaguar development lagged for about two years. After the A.B.C. Dragonfly was proved to be a failure, Siddeley received a Government order for the Jaguar. Development was resumed by S. M. Viale, who re-designed several parts of the engine. J. D. Siddeley decided to remove the supercharger in order to simplify development of the basic design, and by the middle of 1920 the Jaguar was running quite well. In June 1922, by which time the stroke had been increased from 5 inches to 5 1/2 inches, the Jaguar passed the official Air Ministry type test and was ordered in quantities.
  The original Siddeley Siskin ultimately fulfilled its first conception, for it was fitted with an early Jaguar engine in place of the erratic Dragonfly. The airframe design was subsequently considerably modified and, as the Armstrong Whitworth Siskin, equipped several R.A.F. fighter squadrons and appeared in other forms.


SPECIFICATION
  Manufacturers: The Siddeley-Deasy Motor Car Co., Ltd., Park Side, Coventry.
  Power: 320 h.p. A.B.C. Dragonfly I.
  Dimensions: Span: upper 27 ft 6 in. Length: 21 ft 3 in. Height: 9 ft 9 in.
  Areas: Wings: 247 sq ft.
  Weights and Performance: No. of Trial Report: M.260. Date of Trial Report: July, 1919. Type of airscrew used on trial: A.B.8979. Weight empty: 1,463 lb. Military load: 218 lb. Pilot: 180 lb. Fuel and oil: 320 lb. Loaded: 2,181 lb. Maximum speed at 6,500 ft: 145 m.p.h.; at 10,000 ft: 143-5 m.p.h.; at 15,000 ft: 139 m.p.h. Climb to 6,500 ft: 4 min 30 sec; to 10,000 ft: 7 min 50 sec; to 15,000 ft: 13 min 50 sec. Service ceiling: 23,800 ft.
  Armament: Two fixed and synchronised Vickers machine-guns mounted on top of the fuselage, firing forward.
  Serial Numbers: C.4541-C.4546.