O.Tapper Armstrong Whitworth Aircraft since 1913 (Putnam)
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.
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).