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Grumman G-21 Goose

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G-21/JRF Goose
Role Transport amphibious aircraft
Manufacturer Grumman
First flight 1937
Primary users United States Navy
United States Army Air Forces
Royal Air Force
Royal Canadian Air Force
Number built 345

The Grumman G-21 Goose is an amphibious aircraft 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-engined aircraft, and its first aircraft to enter commercial airline service. During World War II, the Goose became an effective transport for the US military (including the United States Coast Guard), as well as serving with many other air forces. During hostilities, the Goose took on an increasing number of combat and training roles.

Design and development

Preserved ex-British JRF-6B Goose in U.S. Navy JRF-1 markings

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.[1] 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.[2]

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.[3]

Modifications

McKinnon G-21G Turbo Goose conversion with 680 shp Pratt & Whitney Canada PT6A-27 turboprops

A number of modifications were made for the Goose, but the most numerous are those by McKinnon Enterprises of Sandy, Oregon, which holds 21 supplemental type certificates (STCs) for modifying G-21-series aircraft and which also manufactured four different conversions that were recertified under a separate FAA type certificate (TC no. 4A24) as brand-new "McKinnon" airplanes.[4] The first was the McKinnon model G-21C which involved replacing the original R-985 radial engines with four Lycoming GSO-480-B2D6 piston engines. It was approved under TC 4A24 on November 7, 1958, and two examples were built in 1958–1959.

The second McKinnon conversion was the model G-21D, which differed from the G-21C only by the insertion of a 36-inch (91-cm) extension in the nose section of the aircraft in front of the cockpit, and 12-inch (30-cm) extensions that were added to the horizontal stabilizers and elevators. The extended nose of the G-21D was distinguishable by the addition of two new windows on each side, and it housed four additional passenger seats. Only one G-21D was built and it was actually reconverted from the first G-21C. When later further converted to turbine engines, it was nicknamed "Turboprop Goose".

After the turbine conversion of the G-21D, McKinnon developed an STC (SA1589WE) to install the same 550-shp Pratt & Whitney Canada PT6A-20 engines on Grumman G-21A aircraft that were still certified under the original TC no. 654. Two G-21A aircraft were modified as “Hybrid” turbine conversions, one by Marshall of Cambridge in the UK (using McKinnon STC kits shipped over from Oregon) and one belonging to the Bureau of Land Management (an agency of the US Department of the Interior in Alaska) being modified by McKinnon in 1967. Because they also had many other McKinnon features installed on them using some of its STCs, these aircraft were later confused with similar but subsequent McKinnon turbine conversions and model G-21E aircraft, but they actually remained “Grumman G-21A” aircraft under TC no. 654; they were never officially recertified under McKinnon’s TC 4A24.

In addition to the two G-21A “Hybrid” turbine conversions, McKinnon converted two other G-21A aircraft in 1968 to a turbine configuration, claiming they were simultaneously recertified as models G-21C under TC 4A24, Section I, and as turbines per STC SA1320WE. However, they apparently lacked some of the internal structural reinforcements that were part of the model G-21C design and were unrelated to the turbine engine transplant from the four Lycoming GSO-480-series piston engines, as a result of which, they were certified to operate up to a maximum gross weight of only 10,500 lb. McKinnon dubbed these aircraft model G-21C “Hybrids”, but one year after they were built, their configuration was approved by the FAA as a whole new model under TC 4A24.

The third McKinnon model, the G-21E, is based on the previous G-21C “Hybrid” conversions. It was initially certified with the same two 550-shp PT6A-20 turboprops used on the G-21D turbine conversion, but later, after approval of the model G-21G, 680-shp (507-kW) Pratt & Whitney Canada PT6A-27 engines were approved as an option on the G-21E. Only one example was ever actually built and recertified as a model G-21E, and it was, in fact, equipped with the more powerful PT6A-27 engines.

The final McKinnon variant is the G-21G, which was approved by the FAA on August 29, 1969, under Section IV of TC no. 4A24. The G-21G combines all of the structural reinforcements and 12,500-lb gross weight of the earlier G-21C and D models, as well as their other features such as the “radar” nose, the “wraparound” windshield, retractable wingtip floats, and “picture” cabin windows, with the more powerful PT6A-27 turbine engines and other minor details to produce the ultimate McKinnon Goose conversion.

New production

In November 2007, Antilles Seaplanes of Gibsonville, North Carolina, announced it was restarting production of the turbine-powered McKinnon G-21G Turbo Goose variant, now identified as the Antilles G-21G Super Goose.[1] Pratt & Whitney Canada PT6A-34 turboprops flat-rated to 680 shp (507 kW) would have replaced the original PT6A-27 engines,[1] and the airframe systems and especially the avionics (aviation electronics – i.e. radios and navigation systems) would have been updated with state-of-the-art “glass panel” instrumentation and cockpit displays. However, as of 2009, Antilles Seaplanes' manufacturing center has been foreclosed and sold at auction. The fate of new Goose production is currently unknown.[5]

Operational history

Goose of the Royal Air Force
Grumman G-21A of Alaska Island Air in 1989

Envisioned as corporate or private "flying yachts" for Manhattan millionaires, initial production models normally carried two to three passengers and had a bar and small toilet installed. In addition to being marketed to small air carriers, the G-21 was also 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 Royal Air Force, which, in a common naming convention with all of its aircraft, designated the type as "Goose".

After the war, the Goose found continued commercial use in locations from Alaska to Catalina and the Caribbean.

A total of 345 were built, with about 30 known to still be airworthy today (although around 60 are still on various civil registries, many of them are known to have crashed or been otherwise destroyed), most being in private ownership, some of them operating in modified forms.[6]

Variants

G-21
The original production version, these were powered by two 450-hp (336-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.[7]
G-21A
Increased in gross weight (8,000 lb (3,636 kg)), 30 of these were built.[7]
G-21B
Built as export coastal patrol flying boats armed with .30 cal machine gun in bow and dorsal hatches and two 100-lb (45-kg) bombs underwing, 12 were built for Portuguese Naval Aviation.[7]
G-21C
Conversion by McKinnon Enterprises, these were re-engined with four 340-hp (254-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 “picture” (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 (serial nos. 1201 and 1202) in 1958–1959, and two other airframes subsequently were converted in 1968, but with two 550-shp (579-eshp, 432-kW) Pratt & Whitney Canada PT6A-20 turboprops per STC SA1320WE as G-21C “Hybrids” (serial nos. 1203 and 1204). Two G-21C “Hybrids” were actually identical to the later 10,500-lb model G-21E, but they were never certified as such.[8]
G-21D
One G-21C was further converted by McKinnon with an extended bow section marked by two extra windows on each side and accommodating another four passengers (serial no. changed from 1201 to 1251 in conjunction with recertification as model G-21D in June 1960.) In 1966, it was re-engined with two 550-shp (579-eshp, 432-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”.[9]
G-21E
A fully certified new model, it was based on simplified turbine conversion of McKinnon model G-21C, with 550-shp PT6A-20 engines (680-shp Pratt & Whitney Canada PT6A-27 engines optional) and more fuel, but without all of the structural reinforcements of the G-21C. at 10,500 lb (4,763 kg) gross weight. One was converted (serial no. 1211).[4]
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 inexplicably recertified as a supposedly modified McKinnon G-21G in spite of the fact that it was not built by McKinnon nor ever conformed to the model G-21G type design.[10][11]
G-21G
The final McKinnon conversion also was fully certified as a new model with 680-shp PT6A-27 engines, 586 US gal of fuel, and 12,500 lb gross weight. Two were converted (serial nos. 1205 and 1226).[12]
The sole Kaman K-16B tilt-wing STOL research aircraft
Kaman K-16B
An experimental tilt wing aircraft, it used the fuselage of a JRF-5 and was powered by two General Electric YT58-GE-2A engines; one was built but unflown.[13][14]
XJ3F-1
The prototype eight-seat utility amphibious plane, it was built for the U.S. Navy; one was built in 1938.[7][15]
JRF-1
A production version of XJ3F-1, five were built for the U.S. Navy.[7]
JRF-1A
Similar to the JRF-1, but with target towing gear and camera hatch added, these five were built for the U.S. Navy.[7]
JRF-2
A version for the U.S. Coast Guard, these had provisions for carrying stretchers; seven were built.[7]
JRF-3
Similar to the JRF-2, these were fitted with autopilot and deicing boots on the wing leading edges to aid operations in Arctic. Three were built for the Coast Guard.[7][16]
JRF-4
Similar to the JRF-1A, these could carry two depth bombs under wing. Ten were built for the Navy.[7]
Grumman JRF-5
JRF-5
A major production version, these incorporated bomb racks from the JRF-4, target towing and camera gear from the JRF-1A, and deicing gear from JRF-3; 184 were built.[7] In 1953, a modified JRF-5 was used to test the landing and takeoff characteristics of hydroskis for the U.S. Navy.[17]
JRF-5G
These 24 JRF-5s were transferred to the US Coast Guard.[7][16]
JRF-6B
A navigation trainer, these were purchased for supply under Lend-Lease; 50 were built.[7]
OA-9
As transport and air-sea rescue for the United States Army Air Forces, 26 were ordered in 1938, supplemented by five JRF-6Bs carrying the same designation.[7][16]
OA-13A
This designation was given to three G-21As impressed by the USAAF.[7][18]
OA-13B
Two JRF-5s were transferred to the USAAF.[7][18]
Goose Mk I
The British designation for three JRF-5s, these were supplied to the Fleet Air Arm.[19]
Goose Mk IA
The British designation for 44 JRF-6Bs, these were supplied under Lend Lease and used for observer training by the 749 Naval Air Squadron in Trinidad.[19]
Goose Mk II
The British designation for two JRF-5s, these were used as staff transports by British Air Commission in the United States and Canada.[19]

Operators

Military operators

Grumman Goose #798 of the Royal Canadian Air Force
Japan Maritime Self-Defense ForceJRF-5
 Argentina
 Australia
 Bolivia
 Brazil
 Canada
 Cuba
 France
 Honduras
 Japan
 Paraguay
 Peru
 Portugal
 Sweden
 United Kingdom
 United States

Governmental operators

 United States
 Canada

Civil operators

British Guiana Airways Grumman Goose circa 1955. Piarco Airport, Trinidad.
 Australia
 British Guiana
 Canada
 Croatia
 Dutch East Indies
 Fiji
 Iceland
 New Zealand
 Norway
1942 Grumman Goose at Akutan, Alaska, operated by PenAir
Grumman Goose NC16913 painted in Pan Am colors at the Cradle of Aviation Museum, Long Island.
 United States

Accidents and incidents

19 November 1943
Grumman JRF-2 of Port Heiden, Alaska {USCG}, crashed with three crewmen and one passenger missing. It was found in 1987.[23]
13 March 1947
A Grumman JRF-6B of Loftleiðir with seven passengers and a pilot crashed immediately after takeoff on Hvammsfjörður by the town of Búðardalur in Iceland. The pilot and four other passengers were rescued by a boat after they evacuated the plane. Three passengers could not evacuate the plane and went down with it under water. One of the passengers rescued did not survive. The pilot and three passengers survived; four passengers were killed.[24]
21 August 1958
N720 crashed in the Brooks Range, near the upper Ivishak River, in Alaska, killing U.S. Fish and Wildlife Agents Clarence J. Rhode and Stanley Fredericksen, and Clarence's son Jack. The crash site was not found until August 23, 1979.[25]
27 January 1961
A JRF-5 of the French Navy crashed, killing Admiral Pierre Ponchardier and five others. This accident led the French Navy to retire all of their Grumman JRF-5 Gooses in the spring of 1961.[26][27]
July 30, 1971
One person was killed and one was injured when a Grumman G-21A taking off from the airport in Greenville , Maine experienced engine failure or malfunction during takeoff. The NTSB determined the probable cause to be the pilot’s lack of familiarity with the plane and fuel mismanagement.[28]
22 June 1972
N1513V of Reeve Aleutian Airways was written off at False Pass, Alaska.[29][30]
2 September 1978
Charles F. Blair, Jr., former Naval Air Transport Service and Pan American Airways pilot and husband to actress Maureen O'Hara, was flying a Grumman Goose that belonged to his company, Antilles Air Boats, from St. Croix to St. Thomas in the U.S. Virgin Islands when it crashed into the ocean due to failure of the left engine. Three passengers and he were killed; seven passengers were severely injured.[31]
3 August 2008
A Grumman Goose of Pacific Coastal Airlines with seven passengers and crew crashed during a flight from Port Hardy to Chamiss Bay. The aircraft was completely destroyed by a fire. There were only two survivors.[32]
16 November 2008
A Grumman Goose of Pacific Coastal Airlines with eight passengers and crew crashed on South Thormanby Island near Sechelt off British Columbia's Sunshine Coast in bad weather during a flight from Vancouver International Airport to Toba Inlet, BC. Only one passenger survived. The company resumed floatplane operations on November 19, 2008.[33]
27 February 2011
A turbine Goose, N221AG, crashed in the United Arab Emirates when it veered immediately after takeoff. Although registered in the US as a McKinnon G-21G, the aircraft was not an actual McKinnon conversion; it was instead actually designed and built by the Fish and Wildlife Service in Alaska, which originally intended it to be recertified as a model G-21F, but that design was never formally approved as such by the FAA.[34]
17 June 2014
A Grumman G-21A Goose lost control in a snowstorm over the Montana/Idaho border and crashed into the parking lot of the Lost Trail Ski Area near the summit of Lost Trail Pass, subsequently catching fire. The plane was completely destroyed, and the pilot, who was the only occupant of the plane, was killed.[35][36]

Aircraft on display

Canada
United States

Specifications (JRF-5 Goose)

British JRF-6B – the only version with blister side windows

Data from United States Navy Aircraft since 1911 [49]

General characteristics

Performance Armament

Notable appearances in media

Main article: Aircraft in fiction, Grumman G-21 Goose

See also

Related development

Related lists

References

Notes
  1. ^ a b c "Goose." Archived 2013-01-01 at archive.today Antilles Seaplanes history page. Retrieved: August 30, 2008.
  2. ^ "Grumman Goose." Archived 2011-08-05 at Wikiwix Aerofiles.com Grumman page. Retrieved: August 30, 2008.
  3. ^ Truelson 1976
  4. ^ a b "FAA Type Certificate no. 4A24". Archived 2017-01-25 at the Wayback Machine FAA. Retrieved: August 26, 2011.
  5. ^ "The Grumman Goose: Replacing an Alaska aviation legend". Anchorage Daily News. Archived from the original on 12 October 2013. Retrieved 3 May 2018. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  6. ^ "Seven confirmed dead in B.C. plane crash." Archived 2012-11-05 at the Wayback Machine canada.com. Retrieved: December 19, 2009.
  7. ^ a b c d e f g h i j k l m n o Francillon and Killion 1993, p.55.
  8. ^ "Aircraft N642" Archived 2012-09-17 at the Wayback Machine FAA Registry. Retrieved: August 26, 2011.
  9. ^ Francillon and Killion 1993, pp. 54–56.
  10. ^ "G-21." Archived 2009-09-29 at the Wayback Machine National Digital Library: Home. Retrieved: June 10, 2009.
  11. ^ "G-21." Archived 2011-08-28 at the Wayback Machine National Digital Library: Home. Retrieved: June 10, 2009.
  12. ^ "Archived copy". Archived from the original on 2014-10-11. Retrieved 2011-08-26. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)CS1 maint: archived copy as title (link) and "Aircraft – N70AL." Archived 2014-10-11 at the Wayback Machine FAA Registry. Retrieved: August 26, 2011.
  13. ^ "Kaman K-16B Amphibious VTOL Nears Rollout". Aviation Week & Space Technology. January 11, 1960. p. 121. Archived from the original on May 23, 2016. {{cite magazine}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help); Unknown parameter |registration= ignored (|url-access= suggested) (help)
  14. ^ "Kaman K-16B". New England Air Museum. Archived from the original on March 5, 2016. Retrieved February 26, 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  15. ^ Green 1968, pp. 169–170.
  16. ^ a b c Donald 1995, p. 145.
  17. ^ "Hydro-Skis On Seaplanes Speed Take-Off." Popular Mechanics, January 1953, p. 119.
  18. ^ a b Green 1968, p.169.
  19. ^ a b c March 1998, p.127.
  20. ^ Thetford, 1978, p.592
  21. ^ "Grumman Goose has served coast for many years as 'flying-boat workhorse'." Archived 2012-11-05 at the Wayback Machine canada.com. Retrieved: December 19, 2009.
  22. ^ http://www.timetableimages.com Archived 2017-09-12 at the Wayback Machine, June 1, 1969 Alaska Airlines system timetable
  23. ^ "US Coast Guard Aviation casualties". uscg.mil. Retrieved 3 May 2018.
  24. ^ "ASN Wikibase Occurrence # 27712". Archived from the original on 10 August 2013. Retrieved 10 August 2013. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  25. ^ Wilbanks, William (3 May 1999). "Forgotten Heroes of Alaska". Turner Publishing Company. Retrieved 3 May 2018 – via Google Books.
  26. ^ JRF-5 Goose Archived 2015-05-04 at the Wayback Machine Retrieved: February 26, 2012.
  27. ^ FNCV. "fncv federation nationale combattants volontaires france association". www.fncv.com. Retrieved 3 May 2018.
  28. ^ Lowell, Jessica (30 July 2018). "Plane crashes in Greenville since 1966". Kennebec Journal. Press Herald. Retrieved 16 August 2018.
  29. ^ "N1513V." Archived 2008-10-25 at the Wayback Machine NTSB. Retrieved: December 19, 2009.
  30. ^ "accident." Archived 2005-03-24 at the Wayback Machine NTSB. Retrieved: December 19, 2009. Note: States 1970 as year!?
  31. ^ "Antilles Air Boats, Inc., Grumman G21A, N7777V". Accident Reports. National Transportation Safety Board. 28 June 1979. Archived from the original on 24 January 2016. Retrieved 18 March 2016. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  32. ^ "5 dead in B.C. plane crash."[permanent dead link] TheGlobeAndMail.com. Retrieved: December 19, 2009.
  33. ^ "7 dead in plane crash off B.C. coast." Archived 2012-11-03 at the Wayback Machine CBC News, 16 November 2008. Retrieved: December 19, 2009. Viewable: https://web.archive.org/web/20121103203609/http://www.cbc.ca/news/canada/british-columbia/story/2008/11/16/bc-081115-plane-crash.html
  34. ^ "Plane crash kills 4 in UAE" Archived 2011-03-01 at the Wayback Machine CNN News, February 28, 2011. Retrieved: February 28, 2011.
  35. ^ "Archived copy". Archived from the original on 2014-06-18. Retrieved 2014-06-18. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)CS1 maint: archived copy as title (link)
  36. ^ Missoulian. "Pilot killed in Lost Trail crash; witnesses describe fireball". billingsgazette.com. Archived from the original on 4 May 2018. Retrieved 3 May 2018. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  37. ^ "GRUMMAN G-21A GOOSE II". Ingenium. Ingenium. Retrieved 6 August 2018.
  38. ^ Dupas, Ron. "No. 406B. Grumman G-21A Goose (CF-MPG c/n B.77) Royal Canadian Mounted Police". 1000AircraftPhotos.com. Retrieved 7 August 2018.
  39. ^ "Grumman G-21 Goose". Smithsonian National Air and Space Museum. Smithsonian Institution. Retrieved 6 August 2018.
  40. ^ "JRF GOOSE". National Naval Aviation Museum. Naval Aviation Museum Foundation. Retrieved 7 August 2018.
  41. ^ "Airframe Dossier - Grumman G-21/JRF/OA-9/OA-13 Goose, c/n 1085, c/r N12CS". Aerial Visuals. AerialVisuals.ca. Retrieved 7 August 2018.
  42. ^ ""Save The Goose Project"". Tongass Historical Society. Retrieved 6 August 2018.
  43. ^ Dudzak, Maria (26 May 2016). "Volunteers progress on Goose restoration". KRBD. Rainbird Community Radio. Retrieved 6 August 2018.
  44. ^ "FAA REGISTRY [N88821]". Federal Aviation Administration. U.S. Department of Transportation. Retrieved 6 August 2018.
  45. ^ Miller, Phil (1 May 2017), "VISITOR TO THE MUSEUM" (PDF), Flightplan, Evergreen Aviation and Space Museum, p. 6, retrieved 7 August 2018
  46. ^ "FAA REGISTRY [N7811]". Federal Aviation Administration. U.S. Department of Transportation.
  47. ^ "Airframe Dossier - Grumman JRF-5 Goose, s/n 87736 USN, c/n B-130, c/r N644R". Aerial Visuals. AerialVisuals.ca. Retrieved 6 August 2018.
  48. ^ "Grumman G-21 Goose". Cradle of Aviation Museum. Retrieved 6 August 2018.
  49. ^ Swanborough and Bowers 1976, p.212.
  50. ^ Green 1968, p.171.
Bibliography
  • Donald, David, ed. American Warplanes of World War II. London: Aerospace Publishing, 1995. ISBN 1-874023-72-7.
  • Francillon, René J. and Gary L. Killion. "Sauce for the Goose – turbine style". Air International, July 1993, Vol. 45, No 1, pp. 53–57. Stamford, UK:Key Publishing. ISSN 0306-5634.
  • Green, William. War Planes of the Second World War: Volume Five Flying Boats. London:Macdonald, 1968. ISBN 0-356-01449-5.
  • March, Daniel J., ed. British Warplanes of World War II. London: Aerospace Publishing, 1998. ISBN 1-874023-92-1.
  • Swanborough, Gordon and Peter M. Bowers. United States Navy Aircraft since 1911. London: Putnam, Second edition, 1976. ISBN 0-370-10054-9.
  • Thruelsen, Richard. The Grumman Story. New York: Praeger Publishers, Inc., 1976. ISBN 0-275-54260-2.
  • Winchester, Jim, ed. "Grumman Goose/Mallard." Biplanes, Triplanes and Seaplanes (The Aviation Factfile). Rochester, Kent, UK: Grange Books plc, 2004. ISBN 1-84013-641-3.

Further reading

Wikimedia Commons has media related to Grumman G-21.
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