McKinnon Enterprises Inc. began conversions of the Grumman G-21A Goose in 1958 with the installation of 4x 340hp(253kW) Lycomings in place of the 2x 450hp (335kW) Pratt & Whitneys. It is believed that possibly one of these four engined conversions is still airworthy. The majority of the conversions were to turboprop power and included the G-21C and D which featured retractable wingtip floats and enlarged cabin windows as well as interior improvements. The G-21G was similar but with a better appointed interior. The last conversions were completed in 1980 and only a handful remain active. A G-21C is illustrated below.

12 seat amphibian first flown in 1966

Engines: 2x 680shp(507kW) Pratt & Whitney PT6A                                                                          Length: 39’7"(12.06m)                                                                                        Height: 14’6"(4.41m)Wingspan: 50’10"(15.49m)                                                                                              No.built: 20* Range: 1600miles(2574km)                                                          Cruising speed: 190mph(305kmh) Empty weight: 6635lb(3012kg)                                           Maximum take-off weight: 12,500lb(5675kg)

A G-21G is illustrated below.