Curtiss 37 / L-113 Falcon
Curtiss 38 / O-1G Falcon
Curtiss 46 / O-11 / O-39
Curtiss XBT-4 Falcon
Curtiss A-3 Falcon
The US Army Air Service staged two competitions, in late 1924 and early 1925, to find successors to the DH-4 series of observation and light bomber aircraft.
The first Curtiss biplane to bear the name Falcon was the Liberty-powered Curtiss L-113 (Model 37). It was unsuccessful when evaluated in 1924 as the XO-1 in competition with the Douglas XO-2 but was accepted for production the following year when re-engined with a 380kW Packard 1A-1500. It was a conventional unequal-span biplane with a wing of wooden construction that incorporated sweep-back on the outer panels of the upper wing. The fuselage was built up from aluminium tubing with steel tie-rod bracing, and the tail unit included a balanced rudder; the fixed divided landing gear was of tailskid type.
The Packard engine proved a failure, and the 102 production O-1s were fitted instead with various models of the 435-hp Curtiss D-12 (V-1150) engine.
The new biplane went into production as the O-1 (Model 37A) for observation duties with the US Army. The initial order was for 10 aircraft re-engined with a Curtiss D-12. One of these was completed later as the O-1A with a Liberty engine, and the first O-1 was converted to O-1 Special configuration as a VIP transport.
Forty-five examples of the O-1B (Model 37B) were ordered in 1927, this first major production version incorporating such refinements as wheel brakes and an underbelly auxiliary fuel tank which could be jettisoned in flight. They were followed by four O-1C aircraft, part of the O-1B order, converted to serve as VIP transports by enlargement of the rear cockpit and the addition of a baggage compartment. (The designation O-1D was not used).
In 1929 the US Army ordered 41 of the O-1E (Model 37I) with V-1150E engines developed from the original Curtiss D-12. A number of other improvements included the introduction of oleo-pneumatic shock-absorbers, Freise ailerons, and horn balanced elevators. One O-1E was modified subsequently as a VIP transport becoming redesignated O-1F (Model 37J). The XO-1G (Model 38) replacing the twin Lewis guns on a Scarff mounting that equipped the earlier models by a single gun on a post mounting. Other modifications introduced redesigned horizontal tail surfaces and a steerable tailwheel.
The XO-1G was originally an O-1E which had been modified previously to contend as a new US Army basic trainer under the designation XBT-4 (Model 46).
The XBT-4 of 1930 was produced at the Curtiss-Wright experimental facility in Garden City in 14 days. For its training role, the rear cockpit is higher than previous models, and the squared cowling is sloped to give good visibility. A full thickness sponge rubber pad is mounted over the instrument panel with cutouts for the dials. The seats may be raised or lowered 7.5 in, and are tilted back at 13˚ from level. All cockpit mechanism is hidden behind wooden veneer walls.
Successful tests led to construction of 30 series examples of the O-1G with improved strearnlining, slightly smaller wings, and redesigned rear cockpits, were 16 km/h (10 mph) faster than the O‑1B, bringing total O-1 production for the US Army to 127.
Two O-1 conversions (to O-1A and XO-11) to a 420-hp Liberty engine, 66 Liberty-engined models were produced for the US Army.
The O-1 Falcon and its variants saw a decade of service with the observation squadrons of the US Army Air Corps and ended their days with reserve National Guard units. The basic design was adapted also as the A-3 attack biplane which saw considerable use. The A-3, based on the O-1B was an attack version of the Falcon. It had two additional 0.30-in (7.62-mm) machine-guns in the lower wings and could carry up to 91 kg (200 lb) of underwing bombs. The standard armament for most Falcons was four 0.30-in (7.62-mm) guns, two in the wings and a twin mount on a Scarff ring in the rear cockpit.
There were also export versions and a number of commercial Falcons.
Several experimental Falcons flew with 600-hp Curtiss V-1570 Conqueror engines. They included the XO-13 and XO-13A (two converted O-1s) for the 1927 national air races; one O-13B; three YO-13Cs, otherwise similar to the O-1E; one YO-13D (super-charged Conqueror); one XO-16, a Conqueror-engined O-11 with Prestone (ethylene glycol) cooling; and one Y10-26, similar to the O-1E but with a GIV-1570A-geared Con-queror and modified cooling system. How-ever, the only Conqueror-powered production version, was the O-39, with Prestone cooling and a smaller rudder, but otherwise similar to the O-1G. Ten of these were built in 1932. Other one-off engine testbeds included the XQ-12 (Pratt & Whitney Wasp), converted from an O-11, and XO-18 (Curtiss Chieftain). Other conversions, not involving an engine change, were four O-1Bs to O-1C unarmed VIP transports; one O-1E to an unarmed O-1F; another O-1E to XBT-4 basic trainer configuration, this later becoming the prototype for the O- 1G; and one O-11 to O-11A (incorporated the improvements of the O-1E).
Except for the O-1C and O-1F, standard armament on the observation Falcons was four 0.30-in (7.62 mm) machine-guns: two fixed, forward-firing guns in the nose and two on a Scarff ring in the rear cockpit. Between 1927-30, Curtiss also produced 154 attack versions (76 A-3s, based on the O-1B, and 78 A-3Bs, based on the O-1E). These had two additional 0.30-in (7.62-mm) guns in the lower wings and could carry up to 91 kg (200 lb) of underwing bombs. There was also, in 1928, one XA-4, equivalent to the A-3, but with a 421-hp R-1340-1 Wasp engine.
Span: 11.58 m (38 ft)
Length: 8.64 m (28 ft 4 in)
Gross weight: 1989 kg (4385 lb)
Maximum speed: 218 km/h (135.4 mph)
Engine: 1 x 324kW Curtiss V-1150E inline piston engine
Take-off weight: 1972 kg / 4348 lb
Loaded weight: 1325 kg / 2921 lb
Wingspan: 11.58 m / 37 ft 12 in
Length: 8.28 m / 27 ft 2 in
Height: 3.20 m / 10 ft 6 in
Wing area: 32.79 sq.m / 352.95 sq ft
Max. Speed: 227 km/h / 141 mph
Ceiling: 4665 m / 15300 ft
Range: 1014 km / 630 miles
Armament: 1 x 7.62mm machine-gun
Span: 11.58 m (38 ft)
Length: 8.28 m (27 ft 2 in)
Gross weight: 2030 kg (4475 lb)
Maximum speed: 224 km/h (139 mph)