William Douglas, Ltd. of Bristol, UK built motorcycle engines that were converted and developed by the firm into Douglas engines for light aircraft. According to Peter W. Brooks' book (PWB), the Douglas Dryad was the last engine design built before the Douglas firm closed at the end of 1932. The Dryad had been built to an order from G. and J. Weir, Ltd. of Cathcart, Glasgow, Scotland for application to the Weir W.1 autogiro (built under Cierva license with the designation Cierva C.28). The designers of the Dryad were C.G. Pullin and G.E. Walker, who joined the Weir firm in 1933 and developed the Weir O-92 described below for the Weir W.2 autogiro. Pullin and Walker later designed the inverted inline four cylinder Weir Pixie engine for the Weir W.3 and W. 4 autogiros. Aero Engines, Ltd. of Bristol, UK was formed in 1935 and took over the Douglas plant. They planned to manufacture French Hispano-Suiza aircraft engines under license and purchased inverted inline engine designs from UK General Aircraft, Ltd. (Monarch) and from Weir (Pixie). During 1936-1937, Aero Engines also introduced two HOAE of their own design, the O-49 and the O-96, probably based on the Douglas and Weir engines (Ae39), although the details are not known by the compiler.
O-30 -- {N/A / N/A / 30} / {N/A / N/A / 500}
2cyl; Douglas 500cc; N/Ahp@N/A rpm; 1922-1925; Wt = 80#.
Single-ignition engine geared to N/A; set speed (Pixie) and altitude (558) records at the 1923 Lympne and Hendon Air Meets.
AJJ1, 2; AM.
Applications: (UK) Avro 558 [G-EBHW] - see AM7/84; Parnall Pixie I [G-EBKM] - see AM10/80; R.A.E. Zephyr [G-EBGW] - see AM12/84.
O-36 -- {2.677 / 3.228 / 36.3} / {68 / 82 / 596}
Same stroke as O-45 (Digit), O-49.
2cyl; Douglas Dot, 600cc; 18hp@3000rpm; 1923-1927; Wt = 80#.
Single-ignition engine geared to N/A.
Ae39; AJJ1, 2; AM.
Applications: (UK) B.A.C. VII Planette powered glider - see AM10/76; R.A.E. Hurricane [G-EBHS] - see AM12/84.
O-45 -- {N/A / N/A / 45} / {N/A / N/A / 737}
2cyl; Douglas 737cc; 22hp@3500rpm, 30@5500 (TO); 1922-1927; Wt = 72#.
Single-ignition engine geared to N/A.
Ae39; AJJ1, 2; AM.
Applications: (UK) De Havilland D.H.53 Humming Bird [G-EBHX, G-EBHZ] - see AM4/85; Handasyde monoplane - see AM1/85; Parnall Pixie II [G-EBKM] - see AM10/80; Vickers 89 Vigit [G-EBHN] - see AM2/85.
O-45 -- {2.992 / 3.228 / 45.4} / {76 / 82 / 744}
Same stroke as O-36, O-49.
2cyl; Douglas Digit; 22hp@3000rpm; 1925-1932; Wt = 85#.
Single-ignition engine geared to N/A.
Ae39.
Applications: None found.
O-49 -- {3.110 / 3.228 / 49.1} / {79 / 82 / 804}
Same stroke as O-36, O-45 (Digit).
2cyl; Aero Engines Sprite; 23hp@2850rpm, 24@3150 (TO); 1936-1937; Wt = see below.
Engine geared to N/A; single-ignition version was Mk.I with Wt = 78# and double-ignition version was Mk.II with Wt = 86#.
Ae39; AJJ1, 2; AM.
Applications: (Belgium) Tipsy S.2 [OO-TIB] - see AM3/77. (France) Mignet H.M.14 Pou du Ciel [G-AEFW]. (UK) B.A.C. Drone (later Kronfeld Super Drone) - see AM10/76; Gordon Dove [G-AETU] - see AM3/77; Helmy Aerogypt I [G-AFFG] small trimotor.
O-75 -- {3.622 / 3.622 / 74.6} / {92 / 92 / 1223}
2cyl; Douglas Dryad; 36hp@3000rpm, 40@4000, 52@4500 (TO); 1932; Wt = 110#.
Air-cooled, dual-ignition engine reduced through spur gears to 0.556; built for Weir just before Douglas closed at the end of 1932.
Ae39, PWB.
Applications: (UK) Weir W.1 (Cierva C.28) autogiro.
O-92 -- {N/A / N/A / 92} / {N/A / N/A / 1504}
2cyl; Weir Flat Twin; 40-50hp@N/A rpm; 1933-1935; Wt = N/A.
Designed by C.G. Pullin and G.E. Walker for the Weir W.2 autogiro.
PWB.
Applications: (UK) Weir W.2 autogiro.
O-96 -- {3.937 / 3.937 / 95.9} / {100 / 100 / 1571}
2cyl; Aero Engines "1.5 litre engine"; 38-40hp@2800rpm; 1936-1937; Wt = 110#.
Single-ignition engine geared to N/A.
Ae39.
Applications: None found.