The Douglas YB-11/ YO-44/ YOA-5 began life as an amphibian navigational leader and rescue aircraft to operate alongside land based bombers, but was completed as an observation aircraft and didn't enter production.
During 1932 Douglas received orders for twin-engined bombers from both the US Navy and the Army Air Corps. The Army wanted a fast amphibian that could operate alongside ground based bombers, acting as a navigational leader and as an air-sea rescue aircraft to pick up the crews of any bombers lost over water. The Navy wanted a longer range flying boat.
Both designs were based on the Douglas Dolphin, an amphibian that had been developed in the early 1930s. The Dolphin was a high winged flying boat, with fixed wheels mounted on the sides of the fuselage and powered by two radial engines carried in nacelles that were raised above the wing. The Dolphin was produced in a number of variants, most with glazed cabins in the fuselage.
The YOA-5 had a flying boat fuselage with a two-step hull. It had fixed floats two thirds of the way along the cantilevered wings. The wings were high mounted, with tapered front and trailing edges. On the tail the horizontal surfaces were mounted high up the vertical surface, level with the engines.
The aircraft was originally powered by two 670hp Wright R-1820-13 nine-cylinder radial engines, carried in nacelles mounted above the wing. It carried a crew of five and was armed with three .30in machine guns - one in the nose and two in waist positions. The forward part of the wing was covered with corrugated aluminium, while the area behind the rear spar was fabric covered. The main wheels were retractable and pulled up onto the side of the fuselage, where they were surrounded by a fairing.
The idea of using amphibians alongside land based bombers was tried out while the YB-11 was being developed, and had proved to be rather impractical. As a result the YB-11 was redesignated as the YO-44 observation aircraft, and then the YOA-5 observation amphibian. The order was placed on 18 November 1932 and the aircraft made its maiden flight, as the YOA-5, in January 1935. It was delivered to the Army Air Corps on 24 February 1935. After a series of tests the aircraft went to the 1st Air Base Squadron at Langley Field, Virginia.
During its time with the 1st Air Base Squadron the aircraft set two amphibian distance records. On 12 December 1935 it flew 1,033.2 miles non-stop, with LT H. MacCaffery, Capt A. Y. Smith and Lt H. S. Hansell as its crew. On 29 June 1935, with a crew of Major-General F.M. Andrews and Major J. Whittey, broke that record with a flight of 1,429.685 miles. For both of these flights the aircraft had been given 930hp Wright YR-1820-45 engines in place of its original 670hp engines.
In 1936 the aircraft was given two 750hp R-1820-25 engines. It kept these for the rest of its service career. It was based at Langley Field until June 1941, and then at Elmendorf Field, Alaska. The YOA-5 was condemned on 31 December 1943. During its service career it saw some use as an Air Rescue aircraft.
Engine: Two Wright R-1820-45 Cyclones
Power: 930hp each
Span: 89ft 9in
Length: 69ft 9in
Loaded weight: 20,000lb
Max speed: 169mph at sea level
Armament: Three 0.30in machine guns