Parnall Possum
| Possum | |
|---|---|
 |
|
| Role | Experimental bomber |
| National origin | United Kingdom |
| Manufacturer | George Parnall and Co. |
| Designer | Harold Bolas |
| First flight | 19 June 1923 |
| Number built | 2 |
The Parnall Possum was an experimental triplane, with a single, central engine driving wing mounted propellers via shafts and gears. Two of these British aircraft were built in the mid-1920s.
The Parnall Possum was one of few large aircraft having its engine in its fuselage but propellers on its wings. The concept arose immediately after World War I, when The British & Colonial Aeroplane Co., later Bristol, began thinking about large transport aircraft powered by steam turbines mounted in an "engine room" in the fuselage and driving wing-mounted propellers. They intended to develop the idea using their large Bristol Braemar triplane bomber, initially modified to be powered by four 230 hp (172 kW) Siddeley Pumas and called, in anticipation of steam power the Tramp. They sought and obtained Air Ministry support for this project, the Ministry appreciating the extra safety of an aircraft whose engines could be serviced in flight. Consequentially, the Ministry also issued specification 9/20 for a smaller aircraft of the same configuration and placed orders for two prototypes with Parnall, for the single-engined Possum, and with Boulton & Paul for their twin-engined Bodmin. They were described as "Postal" aircraft but were clearly experimental bombers. All three types were built, but only the Possum and the Bodmin flew.
The Possum was a single-bay triplane, with equal span, parallel chord wings without sweep or stagger. The lowest wing joined the lower fuselage longerons and the middle wing the upper longerons, with the upper wing held well above the fuselage on cabane struts. There were ailerons on all wings. The propeller shafts were mounted in the middle wing within small fairings and placed as close to the fuselage as the two-bladed, 9 ft 6 in (2.90 m) propellers would permit. One advantage of the triplane layout was that each propeller shaft could be symmetrically braced with a pair of X-shaped struts to the upper and lower wings. One set of Xs joined the forward spars and the other the rear. The wing structure was fabric-covered wood.
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