The original production model of the Goose was designated simply as the "G-21" and these were powered by a pair of Pratt & Whitney Wasp Junior SB radial piston engines of 450 horsepower each. These had interior spacing for two pilots and up to six passengers though only twelve of the type were produced. The G-21A followed next and were built in thirty examples - becoming the standard to which the original G-21s were brought up to which included an increase to the gross weight from 7,500lbs to 8,000lbs. In its export form, the G-21 was marketed as the "G-21B", a lightly-armed version meant for coastal maritime patrolling. The first customer became the Portuguese Navy. As mentioned, the USAAF variant was the OA-9 and served as a general passenger transport while also called upon to undertake air-sea rescue operations as needed. Only three civilian G-21s became the "OA-13A" while two bomb-armed JRF-5s (detailed below) became the "OA-13B". It is noteworthy here that some wartime military versions of the Goose were pure sea-going aircraft, having their landing gear installations completely removed to save on weight.
When the United States Navy came calling, the G-21 was built into the "XJ3F-1" prototype - a single example appearing in 1938 for US Navy consideration and fitting eight seats in the cabin. This gave birth to the production-minded "JRF-1" of which five were produced. The JRF-1A followed suit but were completed with a hatch for camera facilities and a target towing mount. Five were produced in all. The JRF-2 was built in seven examples with interior room for medical litters meant for US Coast Guard use. The JRF-3 followed in line with the JRF-2 design and also delivered to the USCG though these introduced autopilot and deicers on the leading wing edges for cold weather operations. The JRF-4 was based on the JRF-1A for the USN and added provision for 2 x depth charges to be carried externally under each wing. Ten examples of this type were delivered. The JRF-5 proved the definitive USN/USCG variant with some 184 produced. These were delivered complete with the aforementioned camera facilities and target towing installation of the JRF-1A and the deicing boots of the JRF-3 but also added bomb racks for conventional drop bombs. The JRF-5 was known as the JRF-5G to the USCG of which it received at least 24 from the USN. A naval trainer version was developed for Lend-Lease sale and this was designated as the JRF-6B to which some 50 examples were produced.
In British and Commonwealth service, the G-21 was known simply as the "Goose". In typical British fashion, the aircraft was afforded a series of "marks" to differentiate various production types. This began with the "Goose Mk I" of which three were operated by the Fleet Air Arm. The Goose Mk IA became 44 JRF-6B models procured via Lend-Lease and operated as trainers for the British Navy in the Caribbean. The Goose Mk II were just a pair of JRF-5 models serving as military VIP transports between Canada and the United States.
In post-war America, the G-21 survived largely in operation with the US Department of the Interior of Alaska where its multi-role functionality in varying operating environments were fully put to the test. These were fitted with 2 x Garrett TPE331-2UA-203D series turboprop engines delivering 715 shaft horsepower each. Many others ended up in private ownership or functioning as civilian air taxis for tourists. Today, G-21s still operate mostly in private ownership - a testament to their great engineering and construction. In all, some 345 Grumman Goose aircraft were completed and delivered - an amazing amount (perhaps as many as 30) are still flyable today. Wartime surplus and foreign sales ensured that the Goose managed a healthy postwar life and many were modified by specialist house McKinnon Enterprises as the G-21C, G-21D, G-21E, G-21F and the final McKinnon G-21G "Turbo-Goose". A relatively new initiative by Antilles Seaplanes of North Carolina intends on bringing the Goose to full modern standards with the incorporation of all-digital cockpit facilities, updated flight systems and structural improvements.
For those who managed an existence in front of their television sets during the 1980s, the Grumman Goose could be seen in prominent roles through the Hollywood motion picture / Arnold Schwarzenegger vehicle "Commando" as well as the short-lived ABC television series "Tales of the Golden Monkey".
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