A.Brew Boulton Paul Aircraft since 1915 (Putnam)
Immediately after the Bobolink was cancelled Boulton & Paul's design department began work on a full-scale experimental aircraft, drawings for the wings for example being dated 14 April, 1918. Building such an aircraft was quite an unusual step at the time, given that most pioneering aircraft could be considered full-scale experimental machines, as their designers/builders did not really know if they would fly, or how well, until they tried. That John North should consider it, shows the meticulous way he intended to go about improving the company's design potential.
Because the Defence Regulations introduced in 1917 made it illegal to build an aircraft without official sanction, permission had to be obtained for construction of the P.6. It was registered in a special 'X' series reserved for such aircraft, and given the serial X.25, the last of this special series to be awarded.
The P.6 was a conventional wood and fabric two-seat biplane, the main purpose of which was to examine different aerofoil sections, as part of Boulton & Paul's basic systematic research programme. Having a full-size aircraft was useful for eliminating the errors of scale found in wind-tunnel data.
The wings were single-bay, unstaggered, and equal-span with a basic RAF 15 section. The chord was 5 ft and there was a relatively wide gap also of 5 ft compared with the span of only 25 ft, the forward cockpit being beneath the centre section of the upper wing. The wings were built of spruce spars and ribs, with a spruce leading edge, and an ash trailing edge. The 7 1/2 sq ft area ailerons were identical on upper and lower wings.
The fuselage contained a large number of Sopwith Camel parts, and was a similar box-section design, with slightly curved upper surface. The use of Camel parts was only to be expected as the company were still producing an average of 29 Camels a week. The engine cowling was metal, and left unpainted. The very rounded horn-balanced rudder was of 9 sq ft area compared with only 2 1/2 sq ft for the fixed fin.
The P.6 was powered by the RAF 1a air-cooled V-8 of 90 hp driving a four-blade propeller of 9 ft 3 in diameter. This gave it a speed of 103 mph at 1,000 ft and the 20,1 gal fuel tank gave an endurance of 2 hr 20 min.
The date of the P.6's first flight is unknown, but it is likely to have been late in 1918, the use of Camel parts suggesting construction of the P.6 before Camel production gave way to Snipe production in November. It is probable that Frank Courtney made the first flight, he certainly flew the aircraft on several occasions, and gave Mrs Dawson Paul her first flight in it in March 1919.
Whether interchangeable mainplanes were actually fitted to the aircraft at any time is not recorded, but considerable experimental data was collected from its operation. The P.6 was a handy light aircraft, apart from its experimental usefulness, and after the War was actually offered for sale for ?600, though the company built a slightly larger version, the P.9, as their main offering for the civil flying boom which they hoped would follow.
The P.6 was put to practical use as transport for the company's general sales manager, being registered K-120/G-EACJ on 20 May, 1919; though there is some doubt that the aircraft ever wore these markings, retaining its X.25 serial and RAF roundels in all surviving photographs. It was painted with the large letters Boulton & Paul Ltd, Sales Dept, on the fuselage sides in an early form of aerial advertising, and so became one of the first corporate aircraft, and is credited with making the first business flight, on 1 May, 1919, from Norwich to Bury St Edmunds.
90 hp RAF 1a.
Span 25 ft; length 19 ft; height 8 ft; wing area 235 sq ft.
Empty weight 1,100 lb; loaded weight 1,725 lb.
Maximum speed 103 mph at 1,000 ft; climb to 5,000 ft 9min; endurance 2 hr 20 min.
A.Jackson British Civil Aircraft since 1919 vol.1 (Putnam)
BOULTON AND PAUL P.6
Two-seater powered by one 90-h.p. R.A.F.IA, built at Norwich 1918 for full-scale aerodynamic research. One aircraft only: became civil 1919 as K-129/G-EACJ, c/n X25. Thereafter used as the firm’s executive aircraft. Span, 25 ft. Length, 19 ft. Tare wt., 1,100 lb. A.U.W., 1,725 lb. Max. speed, 103 m.p.h.