the Grumman Goose ! And of course I wanna apply that longevity statement to the smaller Grumman  Widgeon  (inverted Ranger powered), to the bigger Grumman  Mallard  (P&W R-1340 powered), and also to the much bigger Grumman Albatross (Wright R-1820 powered) - a truly amazing family of amphibious aircraft from the 30's