The Grumman G-21 Goose is an amphibious flying boat designed by Grumman to serve as an eight-seat “commuter” aircraft for businessmen in the Long Island area.
The Goose was Grumman’s first monoplane to fly, its first twin-engine aircraft, and its first aircraft to enter commercial airline service.
During World War II, the Goose became an effective transport for the US military, as well as serving with many other air forces.
During hostilities, the Goose took on an increasing number of combat and training roles.
The G-21 was promoted as a military transport.
In 1938, the U.S. Army Air Corps purchased the type as the OA-9 (later, in the war years, examples impressed from civilian ownership were designated the OA-13A).
The most numerous of the military versions were the United States Navy variants, designated the JRF.
The amphibious aircraft was also adopted by the Coast Guard and, during World War II, served with the Royal Canadian Air Force in the transport, reconnaissance, rescue, and training roles.
The G-21 was used for air-sea rescue duties by the Fleet Air Arm, who assigned the name Goose.
A single aircraft was used briefly by No. 1 Air Ambulance Unit, Royal Australian Air Force in the Mediterranean.
In 1936, a group of wealthy residents of Long Island, including E. Roland Harriman, approached Grumman and commissioned an aircraft that they could use to fly to New York City.
In response, the Grumman Model G-21 was designed as a light amphibious transport.
Grumman produced a high-wing monoplane of almost all-metal construction the trailing half of the main wing and all of the flight control surfaces except for the flaps were fabric-covered.
It was powered by two 450 horsepower (340 kW) Pratt & Whitney R-985 Wasp Junior nine-cylinder, air-cooled, radial engines mounted on the leading edges of the wings.
The deep fuselage served also as a hull and was equipped with hand-cranked retractable landing gear.
First flight of the prototype took place on May 29, 1937.
The fuselage also proved versatile, as it provided generous interior space that allowed fitting for either a transport or luxury airliner role.
Having an amphibious configuration also allowed the G-21 to go just about anywhere, and plans were made to market it as an amphibian airliner.
Variants
G-21
The original production version, these were powered by two 450 hp (340 kW) Pratt & Whitney Wasp Junior SB engines, at 7,500 lb (3,400 kg) gross weight, with six passengers, and 12 were built, all converted to G-21A standards.
G-21A
Increased gross weight (8,000 lb (3,600 kg).
G-21B
Export coastal patrol flying boat armed with .30 in (7.6 mm) machine gun in bow and dorsal hatches and two 100 lb (45 kg) bombs under wing, 12 built for Portuguese Naval Aviation.
G-21C
Conversion by McKinnon Enterprises, these were re-engine with four 340 hp (250 kW) Lycoming GSO-480-B2D6 air-cooled, geared, and supercharged flat-six engines and fitted with retractable wingtip floats, a fiberglass radar nose, a one-piece wraparound windshield, and enlarged cabin windows; gross weight increased to 12,499 lb (5,669 kg) as result of internal structural reinforcements.
Two were converted as piston-powered models G-21C in 1958–1959, and two other airframes subsequently were converted in 1968, but with two 550 shp (410 kW) Pratt & Whitney Canada PT6A-20 turboprops per STC SA1320WE as G-21C Hybrids.
Two G-21C Hybrids were identical to the later 10,500 lb (4,800 kg) model G-21E, but they were never certified as such.
G-21D
One G-21C was further converted by McKinnon with an extended nose marked by two extra windows on each side and accommodating another four passengers.
Recertified as G-21D in 1960.
In 1966, it was re-engine with two 550 shp (410 kW) PT6A-20 turboprops and fitted with revised Alvarez-Calderon electric flaps in accordance with STC SA1320WE, retaining the G-21D designation, but subsequently identified as the McKinnon “Turboprop Goose”.
G-21E
A fully certified new model, it was based on a simplified turbine conversion of the McKinnon G-21C, with 550 shp (410 kW) PT6A-20 engines (680 shp (510 kW) Pratt & Whitney Canada PT6A-27 engines optional) and more fuel, but without all of the structural reinforcements of the G-21C. 10,500 lb (4,800 kg) gross weight.
One converted.
G-21F
A conversion by Fish and Wildlife Service in Alaska (using McKinnon engineering data) with 715 shp (533 kW) Garrett TPE331-2UA-203D turboprops, one was converted, but the FWS model “G-21F” was never approved by the FAA and the one example built was recertified as a modified McKinnon G-21G despite not being built by McKinnon nor conforming to G-21G type design.
G-21G
The final McKinnon conversion also was fully certified as a new model with 680 shp (510 kW) PT6A-27 engines, 586 US gal (2,220 l; 488 imp gal) of fuel, and 12,500 lb (5,700 kg) gross weight.
Two converted.
Kaman K-16B
Experimental tilt wing aircraft, with JRF-5 fuselage powered by two General Electric YT58-GE-2A engines: one built but not flown.
XJ3F-1
Prototype eight-seat utility amphibian, built for the US Navy; one built in 1938.
JRF-1
Production XJ3F-1, built for US Navy.
JRF-1A
Similar to JRF-1, but with target towing gear and camera hatch added, built for US Navy.
JRF-2
U.S. Coast Guard version with provisions for carrying stretchers.
JRF-3
Similar to the JRF-2, fitted with autopilot and de-icing boots on the wing leading edges for Arctic operations, built for US Coast Guard.
JRF-4
Similar to JRF-1A, these could carry two under wing depth bombs, built for US Navy.
Grumman JRF-5
JRF-5
Major production version with bomb racks, target towing and camera gear, and de-icing gear.
In 1953, a modified JRF-5 tested hydro skis for the US Navy.
JRF-5G
24 JRF-5s transferred to the US Coast Guard.
JRF-6B
Navigation trainer purchased for supply under Lend-Lease.
OA-9
Transport and air-sea rescue for United States Army Air Forces, 26 ordered in 1938, supplemented by five JRF-6Bs under the same designation.
OA-13A
Three G-21As impressed by the USAAF.
OA-13B
Two JRF-5s transferred to the USAAF.
Goose Mk.I
British designation for three JRF-5s supplied to the Fleet Air Arm.
Goose Mk.IA
British designation for 44 JRF-6Bs, supplied under Lend Lease for observer training by the 749 Naval Air Squadron in Trinidad.
Goose Mk.II
British designation for two JRF-5s staff transports for British Air Commission in the United States and Canada.
