The Douglas O-2 was an observation aircraft manufactured by the Douglas Aircraft Company in the 1920s.
This aircraft family originated from two XO-2 prototypes, the first of which was powered by a Liberty V-1650-1 V-engine with 420 hp (313 kW) and test-flown in the autumn of 1924.
The second XO-2 was powered by a Packard 1A-1500 Vee engine with 510 hp (380 kW), which proved to be unreliable.
In 1925, the US Army ordered 45 O-2 production aircraft, which retained the XO-2’s welded steel tube fuselage, wooden wings, and overall fabric covering, while introducing aluminium panels on the forward fuselage.
The production aircraft specified the long-span wings, which provided improved handling.
The fixed tailskid landing gear included a main unit of the divided type, the horizontal tail surface was strut-braced, and the engine was cooled by a tunnel radiator.
The O-2 was a conventional but highly reliable biplane that attracted orders for 25 more aircraft, including 18 O-2A machines equipped for night flying and six O-2B dual-control command aircraft for the US Army.
Additionally, one civil O-2BS was modified specifically for James McKee, who made a remarkable trans-Canada flight in September 1926.
In 1927, the O-2BS was adapted as a three-seater with a radial engine.
The O-2Hs were an entirely new design but continued the same basic model number.
The major differences included heavily staggered wings, a more compact engine installation, and clean landing gear secured to the fuselage. Variants XO-2 Two pre-production prototypes. O-2 Initial production model – 45 built. O-2A O-2 with night flying equipment – 18 built. O-2B Dual control version of O-2 – six built. O-2C These differed from the O-2 in having frontal radiators for their Liberty L-12 engines and modified oleo-strut landing gear. The USAAC took delivery of 18 aircraft, while the remaining 27 went to reserve National Guard units – 45 built and one later converted from O-9. O-2D Unarmed staff transport versions of the O-2C – two built. O-2E A one-off aircraft that replaced the wire link between upper and lower wing ailerons of production aircraft by rigid struts. O-2H The fuselage was redesigned, and a new tailplane was fitted, with staggered wings of unequal span. The O-2H incorporated the rigid-strut aileron interconnections of the O-2E. An improved split-axle landing gear was standard. The USAAC received 101 O-2Hs between 1928 and 1930, and the National Guard a further 40 – 141 built. O-2J Unarmed dual control version of the O-2H for service as USAAC staff transports – three built. O-2K A slightly modified version of the O-2J for US Army staff transport and liaison duties. 30 built for the USAAC and 20 for the National Guard – 50 built. O-2M various export versions of O-2 that saw services with the Republic of China Air Force. These aircraft were used as scout-bombers by the Chinese in the Second Sino-Japanese War with some success against ground targets of the Empire of Japan. It was also used by the Mexican Air Force with Lewis and Vickers machine guns, with very good results. O-2MC Export version for China, powered by a Hornet radial engine – ten built. O-2MC-2 Export version for China, with the Hornet radial engine surrounded by a Townend ring – 20 built. O-2MC-3 Export version for China, fitted with an uprated 575 hp (429 kW) Pratt & Whitney Hornet radial engine – five built. O-2MC-4 Export version for China – 12 built. O-2MC-5 Export version for China, fitted with the less powerful 420 hp (310 kW) Pratt & Whitney Wasp C1 engine – 12 built. O-2MC-6 Export version for China, fitted with the 575 hp (429 kW) Wright R-1820-E radial engine – 22 built O-2MC-10 Export version for China, fitted with a 670 hp (500 kW) Wright R-1820-F21 radial engine – one built XO-6 Five all-metal O-2s, built in the mid-1920s by Thomas-Morse. XO-6B Radically altered (smaller and lighter) version of the XO-6 – one built. O-7 Three O-2s refitted with the 510 hp (380 kW) Packard 2A-1500 direct-drive engine. Two were later converted to O-2 standards, and one to the O-2C standard. O-8 One O-2 with the 400 hp (300 kW) Curtiss R-1454 radial engine instead of the intended Packard inverted-Vee engine. It later became an O-2A. O-9 One O-2 refitted with the 500 hp (370 kW) Packard 3A-1500 geared engine. It resembled the O-7 but had a four- rather than two-bladed propeller. It later became an O-2A. XO-14 One reduced-scale O-2H, with a 220 hp (160 kW) Wright J-5 engine, and the first Douglas aircraft with wheel brakes. XA-2 The 46th aircraft of the original O-2 contract was completed as an attack machine with the powerplant of one 420 hp (310 kW) V-1410 Liberty inverted-V engine, and with a total of eight machine guns. It was remarkably well-armed for its day and competed against the Curtiss A-3 in 1926 but was not selected for production. OD-1 Two O-2Cs for service with the US Marine Corps from 1929. O-22 O-2H airframe with a swept-back upper wing and a Pratt & Whitney Wasp engine. O-25 O-2H airframe with a Curtiss Conqueror engine, and a revised nose. Later redesignated as the XO-25A O-25A Forty-nine production versions of the O-25. O-25B Three unarmed O-25As fitted with dual controls. Used as staff transport aircraft. O-25C 29 production O-25s with Prestone cooling system. Y1O-29 Later designated O-29A: Two O-2K airframes fitted with a Wright R-1750 Cyclone engine. O-32 O-2K conversion with Pratt & Whitney R-1340-3 Wasp engine, later fitted with anti-drag rings. O-32A Production O-32, 30 built. YO-34 O-22 re-fitted with a Curtiss Conqueror engine. BT-1 O-2K conversion to basic trainer, 30 converted. BT-2 O-32 airframe converted to basic trainer. BT-2A O-32A conversion to basic trainer, 30 converted. BT-2B First production model, 146 built. 58 later converted to BT-2BI instrument trainers. Two converted to BT-2BR and 15 to BT-2BG radio-controlled aerial target drones. BT-2C Second production model, 20 built. 13 converted to BT-2CI instrument trainers. Seven became BT-2CR drone controllers. A-4 Seventeen BT-2BRs and BT-2BGs converted in 1940 as radio-controlled aerial target drones. These had tricycle gear with the main gear moved aft, faired-over rear cockpit, and single controls, allowing the aircraft to be test-flown. MO-2B Three seat general-purpose biplane derived from the M series of mail-planes, despite the O-2 designation. Specifications O2-H Crew 2 Length 30 ft 0 in (9.14 m) Wingspan 40 ft 10 in (12.45 m) Height 10 ft 0 in (3.05 m) Wing area 362 sq ft (33.6 m2) Airfoil Clark Y Empty weight 2,857 lb (1,296 kg) Gross weight 4,484 lb (2,034 kg) Max take-off weight 4,550 lb (2,064 kg) Fuel capacity 110 US gal (92 imp gal; 420 L) in a single fuselage tank ahead of and below the pilot’s cockpit Powerplant 1 × Liberty V-1650-1 V-12 liquid-cooled piston engine, 435 hp (324 kW) Propellers 2-bladed metal propeller Performance Maximum speed 134.5 mph (216.5 km/h, 116.9 kn) at sea level Cruise speed 110 mph (180 km/h, 96 kn) Range 512 mi (824 km, 445 nmi) Service ceiling 16,900 ft (5,200 m) Rate of climb 1,075 ft/min (5.46 m/s) Wing loading 12.4 lb/sq ft (61 kg/m2) Power/mass 0.0971 hp/lb (0.1596 kW/kg) Armament 2 × .30 in (7.62 mm) Browning machine guns, one fixed forward-firing and one flexible 400 lb (181 kg) of disposable stores carried under the lower wing.
Sources McDonnell Douglas Aircraft Company 1st 75 Years Aviation Book-McDonnell Douglas. McDonnell Douglas Aircraft since 1920, Volume 1-René J Francillon. San Diego Air and Space Museum Archive. The National Museum of the U.S. Air Force.
