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The Douglas O-43 was a parasol wing observation aircraft developed from the experimental O-31 and served with the USAAC in small numbers during the 1930s.
The O-31 was a gull winged observation aircraft that made its maiden flight in December 1930. The original version suffered from directional instability, and a series of experiments were conducted to find a solution. These mainly used the first of four YO-31As, which was used to test four wing positions and a tall pointed tail with inset rudder, and the YO-31C, which introduced a cantilevered undercarriage and a bulge in the lower fuselage to give the observer more standing room to fire his gun.
In August 1931 an order was placed for five Y1O-31As (Contract AC-4534). These were completed as the Y1O-43. This used the fuselage of the YO-31C, which had a semi-monocoque fuselage and the bulge for the observer. The Y1O-43 was given a parasol wing, but it retained the cabane wire bracing of the earlier design. It had a shorter vertical fin than on the later O-31s, with a full length rudder. These five aircraft were delivered in the spring of 1933 as the Y1O-43, and entered service as the O-43.
On 2 March 1933 the War Department placed an order for 24 further aircraft. The first 23 were completed as the O-43A. These used a more powerful 675hp Curtiss V-1570-59 engine. They had a deeper fuselage which meant that the ventral bulge was no longer needed. They used a tall fin, with an inset rudder, similar to the design developed for the O-31A. The crew canopy, which had covered the pilot and part of the observer's position on the O-43, was now extended to cover both positions fully. The O-43A also eliminated the large propeller spinner used on the O-43.
The last of these twenty four aircraft was completed as the XO-46, with a 725hp Pratt & Whitney R-1535-6 fourteen cylinder air-cooled radial engine.
The O-43 and O-43A were used by USAAC observation squadrons for some years from 1933, and then went to the National Guard.
O-43A
Engine: Curtiss V-1570-59
Power: 675hp
Crew: 2
Span: 45ft 11in
Length: 33ft 11in
Height: 12ft 3in
Empty weight: 4,135lb
Loaded weight: 5,300lb
Maximum take-off weight:
Max speed: 190mph
Climb Rate: 3.3min to 5,000ft
Service ceiling: 22,400ft