Modelling > 1920s/1930s GB or Between the Wars GB

Siskin Less a Wing

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It is often assumed that the Armstrong-Whitworth A.W.XIII (A.W.13) Aries prototypes were built to Air Ministry Specification F9/26 - the same Siskin-replacement requirement as the 1927 A.W.XIV Starling I biplane fighter. But the A.W.XIII monoplane was not considered a Siskin replacement. Rather it was a 1926 design exercise to see whether a faster-climbing interceptor could be created from the basic Siskin airframe. To that end, two further RAF serials were added to the last of the Siskin IIIA biplanes - J9922 and J9923.

The two A.W.XIII (A.W.13) Aries prototypes differed in powerplant - J9922 retaining the Siskin's proven 14-cylinder Armstrong-Siddeley Jaguar engine. The second prototype, J9923, adopted a new Armstrong-Siddeley radial - the single-row, 9-cylinder Cougar producing 450 hp at altitude. This 1,908 cid radial was intended to compete directly with Bristol's forthcoming Mercury engine. [1] The Cougar was related to Armstrong-Siddeley's bigger twin-row Leopard (the two types sharing 6.0 inch bores and 7.5 inch strokes). This provided commonality of cylinder 'pots' on the factory floor as well as proven technology to incorporate into Armstrong-Siddeley's first foray into larger single-row radial engines.

Top Armstrong-Whitworth A.W.XIII Aries prototype undergoing evaluation at the A&AEE (Aeroplane and Armament Experimental Establishment), RAF Martlesham Heath, Suffolk, October 1930. J9923 was the second prototype Aries, readily distinguished by its single-row Cougar engine. The rear 'lifting struts' is shown deflected at its 'approach' position.

Other than powerplant, the two A.W.XIII prototypes shared common airframes. These were essentially Siskins without their lower, sesquiplane wing panels. Instead, the Aries prototypes had broad, 'lifting struts' to support the upper wing. The major goal was drag reduction but these struts would also assist in reducing landing speed. Each rear strut could pivot around its mounting points to act as an air brake while generating more lift on flare out. [2] This featured proved highly unpopular with evaluation pilots at the A&AEE. The 'lifting struts' were replaced by conventional supports but the Aries was ultimately rejected by the RAF. Both machines were returned to their manufacturer in November 1930.

By this point, Armstrong-Whitworth had abandoned any notion of further developments of the now-dated Siskin airframe. Fighter development emphasis was now placed on the A.W.16 biplane. The A.W.13 prototypes were offered to the Kwangsi Air Force as fighter-trainers to accompany the warlord's A.W.16 order. Accordingly, both Aries prototypes were updated to a common standard. This involved installing a 450 hp Cougar IA in J9922, both airframes being fitted with streamlined NACA cowlings. The variable-incident tailplanes inherited from the Siskin were replaced by a new tail with more in common with that of the A.W.16. Armament was twin synchronized 7.9 mm Vickers machine guns.

The delivery of these revised A.W.13As was considerably delayed. Priority had been assigned to the A.W.16 fighters and there had been some difficulty in securing payments from Kwangsi. The 'Young Marshal', Chang Hseh-liang, had also gotten himself into difficulties with the KMT's Chiang Kai-shek. In an attempt to curry favour, Chang 'gifted' the Kwangsi A.W.13As to the central authority in Nanking. As a result, Armstrong-Whitworth delivered both A.W.13As in the air wing colours of Chiang's National Revolutionary Army. It is not recorded what use the Nationalists made of the A.W.13As. At least one A.W.13A was rumoured to have been re-engined with a Wright 9-cylinder radial but this has not been confirmed.

Bottom Armstrong-Whitworth A.W.13A as delivered in Chinese markings. The specified long-range belly tanks earned the A.W.13A the unflattering nickname of 'D d zhu' ('Pot-bellied Pig'). Also drag-inducing, these tanks were soon deleted in service. China's A.W.13A '601' - shown here - was the first prototype (formerly J9922).

[1] Armstrong-Siddeley's twin-row Jaguar had been facing stiff competition from Bristol's lighter, single-row Jupiter radial. The larger, more powerful Mercury looked set to eclipse both the Jupiter and the heavier Jaguar.

[2] Armstrong-Whitworth came to refer to the Aries as built as the 'A.B.13' - for Armstrong-Bellanca. This reflected Giuseppe Bellanca's strut precedent (with his 1922 Bellanca C.F.). This referencing seems to reflect an settlement with Bellanca.

Interessant, interessant . . .
Of course you'll know that the Siskin replaced the Snipe with the 'Black Diamonds' . . .


Reminds me a bit like a single seat version of a Morane Saulnier MS 230 or MS 315:

Cheers Robin. And as expressed elsewhere, looking forward to your Black Diamond Siskin!

--- Quote from: GTX_Admin on June 17, 2021, 01:45:37 AM ---Reminds me a bit like a single seat version of a Morane Saulnier MS 230 or MS 315:

--- End quote ---

Ooo, there's grist for the mill! Gonna have to do some Frenchies, I think  :smiley:

An AW.16 monoplane would be interesting.


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