The Douglas B-11 was a 1932 project for an amphibian bomber that would fly over water along with formations of conventional land-based bombers to act as navigation leaders and as rescue aircraft in case one of the bombers went down.
A single YB-11 was ordered on November 18, 1932. The serial number was 33-17. It was to have been a substantially scaled-up version of the Douglas Dolphin amphibian and was to have been powered by two 670 hp Wright R-1820-13 Cyclone nine-cylinder radials mounted in individual nacelles above the cantilever monoplane wing. The aircraft was to have had fixed underwing floats and a two-step hull. The main landing gear was to have retracted into fuselage sides just beneath the wing leading edge. Armament was to have consisted of three flexible 0.30-inch machine guns, one firing from each of two gunner's hatches situated on the upper fuselage just behind the wings and one in an enclosed bow turret. The turret was to be have been set back from the bow to allow room for an open mooring hatch in the extreme nose.
While the aircraft was under construction, the Army decided that the use of mixed formations of landplanes and amphibians was not very practical, and the YB-11 was redesignated YO-44, an observation category. It was later redesignated YOA-5, an observation amphibian category.
The YOA-5 was flown for the first time in January of 1935. An open bow gunner position was fitted rather than the originally-intended turret. The YOA-5 was transferred out to Wright Field in Ohio for test and evaluation.
Although the performance of the YOA-5 was acceptable, the Army decided that it did not need observation amphibians and no further examples of the YOA-5 were ordered. YOA-5 33-17 remained a "one-off" aircraft. Following the completion of the tests at Wright Field, the YOA-5 was assigned in October of 1935 to the 1st Air Base Squadron at Langley Field in Virginia. In June of 1941, the YOA-5 was transferred to Elmendorf Field in Alaska. It was scrapped there in late 1943.
Specification of the Douglas YOA-5:
Two 750 hp Wright R-1820-25 air-cooled radial engines. Maximum speed 161 mph at sea level, 170 mph at 2800 feet. Cruising speed 152 mph. Landing speed 75 mph. Service ceiling 18,900 feet. An altitude of 10,000 feet could be reached in 13 minutes. Dimensions: wingspan 89 feet 9 inches, length 69 feet 6 inches, height 22 feet, wing area 1101 square feet. Weights: 14,038 pounds empty, 20,000 pounds gross. Armed with three flexible 0.30-inch machine guns, one firing from each of two gunner's hatches situated just behind the wings and one in an open nose position.