The Curtiss O-1 Falcon was a two-seat biplane observation aircraft that remained in service for more than a decade, from the early 1920s until the mid 1930s, and that was the first in a sizable family of similar aircraft.
The Falcon was originally developed in response to an Air Service design competition for an observation aircraft to be powered by the First World War Liberty engine. The contest was initiated in 1923, and the fly-off took place in 1924. The Liberty powered Falcon (given the Curtiss designation L-113) lost out to the Douglas XO-2, but the Army then decided that the Liberty engine was no longer suitable for front line service.
A new contest was ordered for 1925, this time for aircraft powered by the 510hp Packard 1A-1500 V-12 engine. This time Curtiss won the contest, with a re-engined L-113. The Army placed an order for ten Curtiss O-1 Falcons, changing the engine once again, this time to the Curtiss D-12 (V-115), a similar engine to the Packard.
The O-1 used a novel construction method for 1924, and was built around aluminium tubes that were bolted and riveted together, and braced with steel tie-rods. The wings had a wooden frame, with a wire trailing edge. The lower wing was straight. The upper wing was staggered forward to improve visibility. Its centre section was straight, but the outer panels were swept back at nine degrees. The main wheels were each carried on three struts and it had a tail skid.
The XO-1 was armed with one fixed forward firing .30 Browning machine gun and two flexibly mounted .30 Lewis guns in the observer's position. Small bombs could be carried under the wings.
The O-1 was similar to the prototype, but with an enlarged vertical tail surface. It was powered by the Curtiss D-12 engine. Ten were ordered, but only nine were completed as the O-1, with one becoming the O-1A. Another aircraft was later converted into an unarmed VIP transport, and during 1927 two were turned into XO-13 racers.
The ninth of the ten O-1s was completed with a Liberty engine, a modified rear fuselage and a better rear cockpit. Weight rose by 223lb but speed went up by 4mph.
Forty-five O-1Bs were ordered in 1927. They were similar to the O-1, but with wheel brakes, provision for a droppable under-fuselage fuel tank carting 56 gallons and the ability to dump fuel from the internal fuel tank. One O-11 eventually became an O-1B after a period as a YO-13D.
Four of the O-1Bs were converted to serve as VIP transports during 1927. They were given a baggage compartment and a larger rear cockpit with a door on the starboard side. The guns were removed. They were used by Air Corps generals and members of the President's cabinet.
The designation O-1D was assigned to a version that wound have used the V-1150F engine, but that was never produced.
Forty-one O-1Es were ordered 1929. They had a V-1150E engine, Frise ailerons, horn balanced elevators, shock absorbers on the main undercarriage, a 36 gallon belly tank and an E-4 gun synchronizer. One was built with an enclosed cockpit over the pilot's position. The O-1E was heavier and slightly slower than the O-1B.
Several O-1Es were used a prototypes for other versions of the aircraft. One became the XBT-4, then the XO-1G and finally the Y1O-1G. One became the YO-13C/ O-13 and another the XO-26/ Y1O-26.
The O-1F was the designation given to a single O-1E that was modified to serve as a VIP transport, and that was similar to the O-1D.
The XO-1G was the prototype for the last production version of the O-1. It had been built as an O-1E, and later converted to become the XBT-4 basic trainer prototype. Most of the changes were at the rear of the aircraft. The observer's armament was changed from twin Lewis guns on a Scarff ring to a single machine gun on a post mounting. The horizontal tail surfaces were redesigned and a steerable tail wheel installed. The main wheels had full spats. The XO-1G was later redesignated as a Y1O-1G and finally as a standard O-1G.
The XO-1G was followed by thirty production aircraft, ordered in 1931. They had a modified instrument panel and a new observer's seat, but lacked the wheel spats of the prototype.
The O-11 was a version of the O-1 that was powered by surplus Liberty engines. It was produced for the National Guard.
The XO-12 was a single aircraft powered by the Pratt & Whitney R-1340 Wasp air cooled radial engine
The O-13 was the designation given to versions of the O-1 powered by the Curtiss Conqueror.
The XO-16 had a modified fuselage and a Conqueror engine
The XO-18 was used to test the Curtiss Chieftain engine
The O-26 used a Prestone-cooled geared Conqueror engine.
The O-39 was the last production version, and was powered by the Conqueror engine.
OC/ F8C-1/ F8C-3
The Curtiss OC was the Navy's version of the O-1 Falcon. It was originally ordered as the F8C, but that designation was then used for the F8C Helldiver dive bomber, a rather different aircraft.
US Army Service
The O-1 only saw peace time service with the USAAC. It was used by the 103rd Observation Squadron in 1926-32, and the 97th Observation Squadron from 1935-37, as well as by the 48th School Squadron.
South American D-12 Falcon
The South American D-12 Falcon (Model 37F) was similar to the O-1B, and was powered by the Curtiss D-12, the export and civil designation for the V-1150. Columbia bought one seaplane Falcon in March 1928, followed by fifteen production D-12 Falcons. Peru also purchased ten D-12 Falcons,
Peru was also a customer for the D-12 Falcon, buying ten. The aircraft thus fought on both sides during the Leticia Incident (or Colombia-Peru War of 1932-1933).
In an attempt to establish a market in South America Curtiss set up a factory near Santiago in Chile, where they hoped to produce P-1A Hawks, P-1B Hawks and Curtiss D-12 Falcons, mostly for the Chilean Air Force. The collapse of these scheme left Curtiss with a number of aircraft to sell, including ten or eleven D-12 Falcons. In 1932 nine of these aircraft were sold to the Constitutionalist faction in Brazil and were ferried across Paraguay to Brazil, where they were used against secessionists.
One of the nine aircraft was left in Paraguay, as part of the arrangement to allow the over-flight. This aircraft was used during the Chaco War, where it performed valuable reconnaissance duties. The aircraft survived the war, and remained in use until 1943, when it was finally retired.
Colombia Cyclone Falcon
Colombia was the largest export customer for the Falcon, buying 100 Colombia Cyclone Falcons, powered by 712hp Wright Cyclone air cooled radial engines. Some of these were landplanes, but most were used as twin-float seaplanes. They were armed the standard fixed forward firing machine gun and flexibly mounted rear gun, but also carried two wing mounted guns. The Colombia Falcons had a top speed of 178mph, making them faster than any of the US Army's Falcons. The Colombia Falcon was also used during the Colombia-Peru War of 1932-33.
Bolivia Cyclone Falcon
Bolivia ordered nine Cyclone Falcons late in the Chaco War, with the first aircraft arriving in September 1934. They were similar to the Colombia Cyclone, but lacked the wing mounted guns. One aircraft was lost in September 1934, another was lost in December and two in the fighting early in 1935. The remaining aircraft survived for some time, and one was still officially listed on the Bolivian Air Force's order of battle in January 1949.
Engine: Curtiss V-1150 liquid cooled engine
Length: 28ft 4in
Height: 10ft 1.5in
Empty weight: 2,227lb
Maximum weight: 4,384lb
Max speed: 135.5mph
Service ceiling: 15,425ft
Range: 595 miles
Armament: One or Two fixed forward firing .30in machine guns, two flexibly mounted .30in machine guns in observer's position
Engine: Curtiss V-1150E liquid cooled engine
Length: 27ft 2in
Height: 10ft 6in
Empty weight: 2,922lb
Maximum weight: 4,374lb
Max speed: 141mph
Service ceiling: 15,300ft
Range: 630 miles
Armament: One fixed forward mounted 0.3in Browning machine gun, two flexibly mounted .30in Lewis machine guns on Scarff mounting in observer's position