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The Siddeley-Deasy Sinaia, also known as the Armstrong Whitworth Sinaia and Siddeley Deasy Type 103 was a twin-engine biplane day bomber with gunners in rearwards extensions of the engine nacelles.

Four examples were initially ordered by the Air Ministry in 1917 but only one (serial J6858) was completed. A second example had the serial J6859 allocated but was cancelled. Some sources say it was to be a rival for the proposed Airco DH.8 Coventry Ordnance Works one and a half pound gun fighter project of 1917. This de Havilland design languished at Hendon from 1917 due to the lack of suitable available engines.

The Sinaia was the third and last aircraft design produced by the team led by John Lloyd and F.M.Green at Siddeley-Deasy before they were rebadged by merger as the Sir W.G.Armstrong Aircraft Company. Indeed by the time it flew in 1921 this change had taken effect. It was designed to meet an Air Ministry requirement for a day bomber.

A large twin-engined biplane, its most interesting feature was the arrangement of the defensive armament. The Sinaia's engines were in nacelles mounted on the top of the lower wings and these nacelles were extended rearwards and upwards. Each extension housed a gunner's cockpit at its extremity, fitted with a gun ring. From these positions the gunners would have been able to defend both sides of the bomber independently. The arrangement was described by test pilot Courtney as having, in effect, three fuselages with 'a main fuselage to carry the tail and two other fuselages, extending well aft of the engine nacelles, to carry the gunners'.

It was a three bay biplane with struts to the upper wings from the engine nacelles. The wings had no stagger and were of equal span, though the lower wing was narrower. There were horn balanced ailerons on all of the wings.

The empennage was of biplane configuration with a balanced elevator on the upper plane and containing three balanced rudders. The square section fuselage placed the pilot's cockpit well forward of the engines and a third gunner's position in the extreme, slanted nose. A two wheeled main undercarriage unit was mounted under each engine.

The Siddeley Tiger engine had first run in 1920 and was developed using two modified cylinder banks from the Siddeley Puma, the Tiger was a liquid-cooled 60 degree V12 engine with the advanced feature of an electric starter motor protected by a friction clutch. A reduction gear arrangement was provided for the propeller drive with a ratio of 0.559:1. The company claimed a power output of 600 hp (447 kW) but this was on the optimistic side.

The only aircraft in which the Siddeley Tiger flew was the ill-fated prototype of the twin-engined Siddeley-Deasy Sinaia. The Siddeley Tiger marked the end of the aero engine line originally started by Beardmore and Siddeley-Deasy. The name was later re-used for an 1932 Armstrong Siddeley radial engine.

The first aircraft was assembled at Martlesham Heath. The Sinaia was powered by two 500 hp Siddeley Tiger water cooled engines, a new V-12 design produced by combining two straight-6 Siddeley Pumas onto a single crankshaft. Unsurprisingly this little-tested powerplant proved unreliable and frequent problems with it interrupted the flight trials of the Sinaia.
The project arrived for the flight trials at a time when the original specification had been superseded by events. The war had ended, the company was in the process of a merger and no real enthusiasm for the project existed except to complete the contract. To do this the test flight was required.

Flight testing was undertaken by a Royal Aircraft Establishment test pilot, Frank T. Courtenay and the Sinaia flew for the first time on 25 June 1925.

Initial flights revealed problems and Courtney's opinion of the engine was low and he once said that 'The engines could never be persuaded to run simultaneously for any length of time'.

Several test flights were completed until one October evening flight was affected by slackness in the controls during a landing approach. After landing, the aeroplane was wheeled to the hangar for inspection. It never arrived as the main fuselage buckled in the middle when some fuselage bracing wires came adrift. No one was keen for repairs and the aircraft was taken out of use.
Unfortunately, records relating to the history and performance of the Sinaia were destroyed by enemy action during World War II. From photographs and drawings three gun positions may be noted - two in rearwards-extended engine nacelles - as well as side-by-side seating for the pilot and navigator/wireless operator.

Aircraft Specifications (Sinaia)
Data from Armstrong Whitworth Aircraft since 1913

Crew: 4
Wingspan: 86 ft 10 in
Wing area: 1,823 sq ft
Gross weight: 16,000 lb
Engine: 2 × Siddeley Tiger V-12 watercooled, 500 hp each
Power Loading: 13.3 lb/hp
Wing Loading: 8.9 lb/sq ft
Manufacturer: Siddeley Deasy Motor Car Co., Ltd., Parkside, Coventry.
First flight: 25th June 1921

Engine Specifications (Tiger)
Data from British Piston Engines and their Aircraft

Type: 12-cylinder liquid-cooled inline piston engine
Bore: 6.3 in
Stroke: 7.1 in
Displacement: 2,657 in³
Length: 81.34 in
Width: 33.46 in
Height: 39.57 in
Dry weight: 1,400 lb
Valve train: Overhead camshaft, 4 valves per cylinder
Fuel system: Twin carburettors
Fuel type: Petrol
Cooling system: Liquid-cooled
Power output: 600 hp
Power-to-weight ratio: 0.42 hp/lb

Tapper, Oliver (1973). Armstrong Whitworth Aircraft since 1913. Putnam Publishing. ISBN 0-370-10004-2.
Lumsden, Alec (2003). British Piston Engines and their Aircraft. Airlife Publishing. ISBN 1-85310-294-6.
Courtney, Frank T. (1972). Flight Path. William Kimber. ISBN 0-7183-0482-9.
Flight 1919 (Apr)
Flight 1921 (Sep)
Air Pictorial 1955-11,9673.msg88834/topicseen.html#msg88834 (for context).


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ACCESS: Top Secret
Sep 24, 2009
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Here are a couple more images.


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Senior Member
Jun 25, 2009
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Thanks for writing this article, Cy-27!

Here's a couple more pics:


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