The Loening OL, also known as the Loening Amphibian, was an American two-seat amphibious biplane designed by Grover Loening and built by Loening for the United States Army Air Corps and the United States Navy.
First flown in 1923, the OL was a high-performance amphibian with a large single hull and stabilizing floats fitted underneath each lower wing.
The landing gear was retractable by use of a hand crank in the cockpit, and the plane was equipped with a tailskid for operations on land.
It had a tandem open cockpit for a crew of two.
The aircraft could be flown from either cockpit, with a wheel control in the forward cockpit and a removable stick control in the rear.
Navigation and engine instruments were located in the forward cockpit.
The hull was built of Duralumin on a wooden frame, with five watertight compartments connected through a selector switch to a bilge pump in the rear cockpit.
Plugs in the bottom of each compartment permitted drainage on the ground.
The fuselage was constructed on top of the hull.
The aircraft was strength-tested at Columbia University.
The United States Army Air Corps ordered four prototypes as the XCOA-1, powered by a 400-hp Liberty V-1650-1 engine mounted inverted for clearance of the three-bladed variable-pitch steel propeller.
The engine came with a fire suppression sprinkler system and was encased in a streamlined cowling to protect it from sea spray.
Oil from a tank in the fuselage was cooled by passing through a spiral copper tube exposed to the slipstream on top of the cowling.
The fuel tanks were mounted inside the hull, with a 140-gallon (530-liter) gasoline tank under the wings, and a reserve 60-gallon (230-liter) gasoline-benzol tank between the cockpits.
Total fuel capacity provided for roughly ten hours of flight.
A number of variants were introduced for both the Army and the Navy.
During later production, the company merged with the Keystone Aircraft Corporation.
Four prototypes powered by 400-hp V-1650-1 engines, three later to COA-1
Three prototypes and nine production aircraft for the Army Air Service
Army production aircraft with redesigned vertical tail and powered by a 420-hp, water-cooled Liberty V-12 engine that was mounted inverted, 15 built.
One prototype with a single retractable main wheel and skids fitted to wing floats, powered by an inverted V-12 Wright Typhoon, redesignated XO-10 before delivery in 1929
Same as an OA-1A with a water-cooled V-1650-1 engine, nine built
OA-1B with redesigned fin and rudder, ten built
OA-1C with 480hp Wright IV-1460-1 engine modified tail surfaces and forward-firing machine gun moved to port upper wing, eight built
One XOA-1A redesignated before delivery by the U.S. Army
Naval version with third cockpit, two prototypes powered by a 440-hp Packard 1A-1500
Naval version similar to the COA-1, five built
OL-1 powered by a 475-hp Packard 1A-1500 and other detail changes, four built
OL-3 powered by a 400-hp V-1650-2 engine, six built
Three of these were built for the U.S. Coast Guard in 1926.
OL-3 with a redesigned vertical tail as OA-1C, 28 built
One OL-6 fitted with experimental thicker wing
One OL-6 re-engined with an air-cooled 450-hp Pratt & Whitney R-1340-2 radial engine
As XOL-8 with two cockpits and a 450-hp R-1340-4 engine, 20 built
An OL-8 fitted with arrestor gear, 20 built
An OL-9 with equipment changes, 26 built
An improved version of the OL-6, prototype only
A development of the OA-2 with a 200-hp R-1340-0 engine, project cancelled