The Loening OA-1 was an unusual two-man amphibian aircraft that served with the USAAC in the late 1920s. It differed from contemporary amphibians in that it has a single large float attached to the bottom of the fuselage of what was otherwise a standard biplane. The main wheels were placed on either side of the float and could fold up towards the wing when the aircraft operated on water. As well as using the readily available Liberty Engine, the OA-1 could also use the wings from the DH-4, which had been produced in vast numbers during the First World War.
The first prototype of the OA-1 made its maiden flight in 1923 and it was quickly ordered by the Army. The aircraft was ordered under the 1919-24 designation system, where it became the COA-1, standing for Corps Observation, Amphibian. In 1924 a new designation system was adopted and the COA-1 became the OA-1, for Observation, Amphibian.
The OA-1 was used by the 2nd Observation Squadron, 4th Squadron, 7th Squadron, 14th Squadron, 28th Bombardment Squadron, the 4th Airship Company/ Squadron (later to become the 41st Photographic Reconnaissance Squadron) and the 91st Squadron in the mid to late 1920s. In each case only a small number of OA-1s were used and they were operated alongside a large number of other types.
The OA-1 was also ordered by the Navy, where it became the Loening OL, and the Coast Guard, as the OL-5. A total of 169 aircraft were built for the US Military, 111 for the Navy and 68 for the Army, as well as the three Coast Guard aircraft. In 1928 Grover C. Loening sold his company, but the basic design of the OA continued to be developed by Leroy Grumman, who had worked for Loening, and whose new Grumman Company was largely funded by Loening. The Grumman JF and Grumman J2F Duck were very similar in basic layout to the earlier Loening OA and OL designs.
Four prototypes were produced with the designation XCOA-1. They were powered by the 400hp Liberty V-1650-1 engine.
Nine new aircraft were built as the COA-1. Three of the prototypes were also modified to this standard, for a total of twelve aircraft.
The OA-1A was the second production version of the aircraft, having been re-designated under the 1924 system. It was similar to the COA-1, but with a redesigned tail. Fifteen were built
The OA-1B was similar to the OA-1A. Nine were built.
The OA-1C was similar to the OA-1B, but with a more angular tail. This tail was also used on the OA-2 and on the Navy's OL-6 and later models.
The XOA-1A was a prototype for a version of the aircraft powered by a Wright V-1460-1 Tornado engine. It also featured a new experimental float with a single main wheel that retracted into the float, in place of the two main wheels of the standard OA-1. The engine installation of the XOA-1A was used on the OA-2, while the aircraft itself went to the US Army as the XO-10.
Engine: Liberty V-1650-1