Naval Aircraft Factory (NAF) PN-5 / PN-6 / F-6-L
Immediately after World War I, the emphasis in naval aviation was on carrier operations, and patrol-plane development was carried out on a very limited budget. Building on the F-5-L flying boat-developed from the British-designed Felixstowe F.5 aircraft-the Naval Aircraft Factory (NAF) in Philadelphia produced an improved version of the twin-engine flying boat, which was redesignated PN-5 in 1922. 1 The designation PN-6 was used for two modified variants (originally F-6-L). In 1922 the F6L became Naval Aircraft Factory PN-6.