It was an all-metal , high-winged monoplane powered by two 450 h Pratt & Whitney R-985 Wasp Jr. nine-cylinder , air-cooled radial engines mounted on the leading edge of high-set wings . The typical Grumman rugged construction was matched to an all-metal , high-winged monoplane powered by two 450 h Pratt & Whitney R-985 Wasp Jr. nine-cylinder , air-cooled radial engines mounted on the leading edge of high-set wings .