Boulton & Paul Bolton
| Bolton | |
|---|---|
 |
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| Role | Long-range reconnaissance biplane |
| National origin | United Kingdom |
| Manufacturer | Boulton & Paul Ltd |
| Designer | John North |
| First flight | September 1922 |
| Number built | 1 |
The Boulton & Paul P.15 Bolton was a one-off experimental twin-engined reconnaissance biplane ordered by the Air Ministry to sustain Boulton & Paul's development of steel framed aircraft early in the 1920s. It was the RAF's first metal-framed aircraft.
Just after the end of the World War I the Air Ministry were keen to explore the use of all-steel airframes, partly because during the war spruce stocks had been seriously reduced. They were aware of Boulton & Paul's all-steel-framed, though probably unflown P.10 and the claims of the company designer, John North that such aircraft could be 10% lighter than their wooden framed equivalents. They therefore issued specification 4/20 for a steel framed version of the Boulton Paul Bourges twin-engined reconnaissance bomber and ordered one prototype, so that Boulton & Paul could continue to develop such structures. The P.15 Bolton was the result. Despite its later type number, the Bolton was ordered and flew before the more unusual but equally steel framed P.12 Bodmin. Thus the sole Bolton, serial J6584 was the first metal framed aircraft developed for the Royal Air Force.
In general terms the Bolton was similar to the Bourges, though larger all round; both were twin-engined, three bay biplanes with equal span, constant chord wings with no sweep or stagger. Both carried ailerons on upper and lower wings, though the wingtips of the Bolton were cut off square in the later Boulton & Paul fashion and lacked the protruding balances of the earlier machine. The interplane struts were quite wide chord, their twin triangular members covered in fabric. There were supporting sloping struts from the midpoints of the wing midsection to the upper fuselage longerons. The two 450 hp (336 kW) Napier Lion engines were mounted just inboard of the inner interplane struts, not directly onto the lower wing but rather on (for the top part of the engine was uncovered for air cooling) a little nacelle which had at the front and below the propeller boss, a small radiator. Four-bladed propellers were fitted.
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