The Grumman G-21 Goose was designed and produced by Grumman as an amphibious flying boat that will operate as an eight-seat commuter aircraft for businessmen in the Long Island. It was the first monoplane of the company, as well as its first aircraft fitted with twin engines, and also the first that operated as a commercial aircraft. The Goose was an efficient transport for the United States Military and the United States Coast Guard, together with other air forces throughout the Second World War.
The G-21 Goose was developed by Grumman as a response to the need of a group of wealthy residents in Long Islands for an aircraft that could travel to New York City. The G-21 was a light amphibious transport with high wings and mostly constructed out of metal structures. On May 29, 1937, the prototype conducted its maiden flight.
The JRF-5 was a major production variant with a total number of 184 aircraft built. It could carry up to three crew members and has a five to seven capacity. It has an external length of 11.73 meters, an external height of 3.1 meters, and a fuselage diameter of 1.45 meters. The tail height is 4.93 meters and the wheelbase is 4.3 meters. It has a wingspan of 14.94 meters and a wing area of 34.8 square meters. The empty weight is 2,461 kg, the gross weight is 1,649 kg, and the maximum takeoff weight is 3,629 kg. It has a maximum payload of 1,170 kg and a fuel tank capacity of 220 US gal.
The aircraft is powered by two Pratt and Whitney R-985-AN-6 Wasp Junior engines. It is a nine-cylinder supercharged air-cooled radial piston engine with two overhead pushrod-actuated valves per cylinder, a single-speed gear-driven General Electric centrifugal supercharger with an impeller driven at ten times crankshaft speed, and a direct drive reduction gear. Each engine produces a maximum takeoff thrust of 450 hp and drives three-bladed variable-pitch propellers.
The Goose has a maximum speed of 175 knots at 5,000 feet and a cruise speed of 166 knots at 5,000 feet. The travel range is 560 nautical miles. It can fly up to 21,300 feet and can climb at a rate of 1,100 feet per minute. The aircraft is loaded with two 325 lbs depth charges or two 250 lbs GP bombs.