which quickly absorbed hundreds of pounds of water and was maintenance intensive, so two aircraft with a metal hull of the same shape as the F.5Ls, and fitted with the new wing, were built. Due to reliability problems with the Wright T-2, they were powered by two V-12 Packard 1A-2500 engines. The two PN-9s were converted from PN-8s, after being fitted with a redesigned broad-chord tail to fix a vibration problem. Four PN-10s were built, and while similar to the PN-9, each was given a different engine as the Packard 1A-2500 engines were disappointing. One was fitted with Packard 1A-1500 and another with a Packard 3A-1500, both V-12 water-cooled engines and one each was fitted with the Wright R-1820 and Pratt & Whitney R-1690 radial engines. The wings of the first two Packard powered aircraft had a wood structure, while the second pair with the radial engines had wings with a metal structure, both with a fabric covering. The four PN-11s had a new metal hull with a round turtle deck and lacking the previously characteristic enlarged chines and had a new empennage with twin fins and rudders. One aircraft was fitted with two Wright R-1750 radial engines, while one aircraft were fitted with two Pratt & Whitney R-1690 radial engines as the XPN-11, which was later redesignated as the XP4N-1. Two aircraft were fitted with Wright R-1820 radial engines and while ordered as an XP4N-1 were designated as the XP4N-2 when they entered service. The two metal wing radial-engine powered PN-10s were redesignated as PN-12s, which combined the revised wings of the PN-7 but reverted to the metal hull of the PN-8 with the enlarged chines and was fitted with the more reliable radial engines. The fin was further enlarged, with a straight leading edge. It would see extensive production to re-equip the Navy's patrol squadrons. As the production capacity of the Naval Aircraft Factory was limited, production was contracted out to several aircraft companies, with versions being built by Douglas as the PD-1, by Keystone as the PK-1 and by Martin as the PM-1 and PM-2. These each had their own differences from the PN-12, as the Keystone PK-1 and Martin PM-2 the twin fins and rudders of the PN-11, while the PM-1 and PM-2 also had an enclosed cockpit, and the PK-1 had a modified hull form with a sharper bow. These also formed the basis for