Packard 1A-1500The Packard 1A-1500 was an American 12-cylinder liquid-cooled 60-degree Vee piston aircraft engine designed in 1924. Test flown in the second prototype Douglas XO-2, it proved to be unreliable. Only 29 engines were built.Applications Boeing Model 15 Boeing XP-4 Curtiss Falcon Douglas XO-2 Loening OL