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      Grumman Goose (G-21) Multirole Flying Boat Aircraft  

    Grumman Goose (G-21) Multirole Flying Boat Aircraft

    The Grumman Goose was a true unsung war hero in World War 2, involved in transport, training and at sea rescue operations.

     Updated: 1/19/2017; Authored By Staff Writer; Content ¬©www.MilitaryFactory.com

    While most every aircraft venture usually began with a military requirement or private venture undertaken by a manufacturer for the purpose of sales, the Grumman Goose actually was born out of a privately-funded requirement from wealthy Long Islanders for an amphibious civil-minded air transport to New York City and back. The group therefore commissioned Grumman to design and develop the aircraft to fit such specifications giving rise to the Grumman G-21 "Goose". The Grumman concern delivered a high-wing twin-engine design with a full hull fuselage, roomy exterior and amphibious capabilities to allow for landing on runways or water. The G-21 eventually found military use as an armed patrol craft before, during and after World War 2, sealing the type's legacy for us readers to enjoy today.

    The Grumman G-21 utilized many conventional design avenues of the time and one key initiative was in its liberal use of metal skin - the American aviation industry now having moved away from the wood-and-canvas fabric approach so prevalent following the close of World War 1. Some fabric surfaces were still, however, in play save for some control surfaces but the new aircraft was a most modern endeavor for the era. The fuselage was narrow in the forward profile and very deep to make room for both the passenger cabin and the ship-like hull needed for water landings. The fuselage was capped at the front by a long-running nose assembly giving it the appearance of a speed boat. The fuselage also sported slab sides with windows for viewing and sported a traditional tail section with a short, rounded vertical tail fin and applicable horizontal tailplanes. The cockpit was forward of the passenger cabin with side-by-side seating for two and aft of the nose assembly. Perhaps the most notable element of the aircraft's design (aside from its boat hull) was it high, shoulder-mounted monoplane wing placement running over the roof of the passenger cabin. This allowed for clearance of the propellers utilized by the pair of air-cooled radial piston engines fitted to each wing leading edge. Pontoon floats were affixed at each wing's midway point (outboard of the engine nacelles) for side stability. While designed primarily for operations from water, the aircraft was also completed with a manually-powered and fully retractable three-point undercarriage stance made up of two main landing gear legs and a small tail wheel structure. The main legs retracted into the fuselage sides near the cockpit. With the design completed, the prototype airframe flew for the first time on May 29th, 1937. Upon clearance for civil use, the G-21 served its clients well for they rode in style with the amenities demanded of such a lifestyle. Interiors were of luxury quality and completed with comfortable seating and waste facilities. Little did Grumman - nor its early clients - know that the type would also serve the militaries of the world in very different roles during the world war to follow.

    Seeing value in the rugged, multi-faceted G-21, the United States Army Air Forces (USAAF) decided to procure the type beginning in 1938. These militarized versions were designated in typical Army fashion as "OA-9" mounts meant for aerial observation. The US Navy followed suit and designated their fleet of G-21s as "JRF" with applicable numbered marks following. Along with USN usage, the G-21 was also a mainstay of US Coast Guard operations for a time and these also followed the USN JRF designation marks. By the time of full-scale war, the US military commandeered civilian-minded G-21s into wartime service and designated these as "OA-13".

    Overseas, the G-21 also saw extended use with its most notable operators being the British Royal Air Force and the Royal Canadian Air Force - both used in military roles. It was the British that assigned the nickname of "Goose" to the line and the name stuck to the series from then on (similar to the use of names given to the "Lee", "Grant" and "Sherman" US tanks used by the British Army under Lend-Lease). Other global operators eventually became Argentina, Australia, Bolivia, Brazil, Cuba, France, Honduras, Japan, Paraguay, Peru, Portugal and Sweden - all in military roles. The Imperial Japanese Navy actually evaluated the G-21 as the "Grumman LXG" but did not procure the aircraft prior to the war. In their civilian guise, the G-21 operated in Australia, British Guiana, Canada, the Dutch East Indies, Fiji, Iceland, New Zealand and Norway - wherever rugged qualities and lack of runway facilities was a concern, the G-21 just might be found.

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    Grumman JRF-5 Goose Technical Specifications

    Service Year: 1937
    Type: Multirole Flying Boat Aircraft
    National Origin: United States
    Manufacturer(s): Grumman - USA
    Production Total: 345

    Structural (Crew Space, Dimensions and Weights)

    Operating Crew: 2
    Length: 38.52 feet (11.74 meters)
    Width: 49.02 feet (14.94 meters)
    Height: 16.17 feet (4.93 meters)

    Weight (Empty): 5,437 lb (2,466 kg)
    Weight (MTOW): 8,016 lb (3,636 kg)

    Installed Power and Standard Day Performance

    Engine(s): 2 x Pratt & Whitney R-985 Wasp Junior AN-6 9-cylinder air-cooled radial piston engines developing 450 horsepower each.

    Maximum Speed: 201 mph (324 kph; 175 knots)
    Maximum Range: 640 miles (1,030 km)
    Service Ceiling: 21,306 feet (6,494 meters; 4.04 miles)
    Rate-of-Climb: 1,100 feet-per-minute (335 m/min)

    Armament / Mission Payload

    Usually none unless for armed military use.

    1 x 0.30 caliber machine gun in bow position
    1 x 0.30 caliber machine gun in dorsal position
    2 x 100lb bombs underwing

    2 x 250lb depth charges or conventional drop bombs underwing.

    Global Operators / Customers

    Argentina; Australia; Bolivia; Brazil; British Guiana; Canada; Cuba; Dutch East Indies; Fiji; France; Honduras; Iceland; Japan; Norway; Paraguay; Peru; Portugal; Sweden; United Kingdom; United States

    Model Variants (Including Prototypes)

    G-21 - Initial Production Model; seating for six passengers; 12 examples produced.

    G21A - Improved version; increased weight; 30 examples produced.

    G-21B - Export Armed Patrol Variant; fitted with 2 x 0.30 caliber machine guns and provision for 2 x bombs; Portuguese Navy service; 12 examples delivered.

    G-21C - McKinnon Conversion Model; 4 x Lycoming GSO-480 supercharged engines of 340 horsepower; various modifications.

    G-21D "Turboprop Goose" - McKinnon Conversion Model; lengthened bow; additional passenger windows and increased passenger seating; fitted with 2 x Pratt & Whitney Canada PT6A-20 turboprop engines of 550 horsepower.

    G-21E - McKinnon Conversion Model; 2 x Pratt & Whitney Canada PT6A-20 engines of 550 horsepower; increased fuel stores; single example.

    G-21F - McKinnon Conversion Model; Alaska Fish and Wildlife version based on McKinnon information; fitted with 2 x Garrett TPE331 series turboprop engines of 715 horsepower.

    G-21G "Turbo-Goose" - McKinnon Conversion Model; final McKinnon offering; fitted with 2 x Pratt & Whitney Canada PT6A-27 series engines of 680 horsepower; 2 examples completed.

    XJ3F-1 - US Navy prototype; single example

    JRF-1 - Initial US Navy production model based on the XJ3F-1 prototype; 5 examples produced.

    JRF-1A - Based on the JRF-1; completed with camera facilities and target tow installation; 5 examples produced.

    JRF-2 - USCG variant of the JRF-1; room for medical litters; 7 examples completed.

    JRF-3 - Based on JRF-2 model; USCG use; completed with autopilot and wing deicing feature; 3 examples.

    JRF-4 - Based on JRF-1A; USN use; provision for depth charges to be held underwing; 10 examples produced.

    JRF-5 - Definitive production mark; provision for bombs; installation of camera gear and target tow system; wing deicing system; 184 examples produced.

    JRF-5G - USCG version of JRF-5 model borrowed from USN; 24 examples.

    JRF-6B - Lend-Lease Export Trainer; 50 examples; used in navigational training by RAF in Caribbean.

    OA-9 - USAAF transport or air-sea rescue platform; 26 examples later joined by 5 JRF-6B mounts sharing same designation.

    OA-13A - G-21A civilian models commandeered by USAAF for wartime use; 3 examples.

    OA-13B - JRF-5 in USAAF service; 2 examples transferred.

    Goose Mk I - British Designation of JRF-5; 3 examples.

    Goose Mk IA - British Designation of JRF-6B trainers; 44 examples.

    Goose Mk II - British Designation of JRF-5 for VIP military transport; 2 examples.

    Grumman LXG - One-off example evaluated by IJN; never procured.