PK-1 was retired. Three Martin PM-1s were also supplied to the Brazilian Navy in 1930, and used in bombing raids during the 1932 revolution. Variants PN-5 Redesignated Felixstowe F5L PN-6 Redesignated F-6L. Last two Naval Aircraft Factory F5Ls, modified with revised tail surfaces. PN-7 Modified version with new wings with high-lift thick aerofoil section and wingspan reduced from 103 ft 9 in to 72 ft 10 in (from 32 m to 22 m). Powered by two Wright T-2 engines. Two built. PN-8 PN-7 with metal hull. Powered by two Packard 1A-2500 V-12 engines. Two built. PN-9 Converted from PN-8 with redesigned engine nacelles. One converted. PN-10 Similar to PN-8. Powered by two Packard 1A-2500. Two built. PN-11 New hull eliminating sponsons, fitted with twin vertical tail surfaces. Four built, one with two Pratt & Whitney R-1690 Hornet engines, and remaining three powered by two Wright R-1750D Cyclone. XP4N-1 Improved PN-11; three aircraft ordered, originally designated XP2N but redesignated XP4N-1 before delivery. Last two aircraft completed as XP4N-2s. XP4N-2 Improved XP4N-1 with additional fuel capacity. PN-12 Development of PN-10 powered by radial engines. Two built. One powered by two Pratt & Whitney Hornet engines, with the other powered by two Wright R-1750 Cyclone engines. Douglas PD-1 Developed production version of PN-12. Two Wright R-1750 Cyclone engines. 25 built by Douglas. Keystone PK-1 Production version of PN-12. Twin tails. Two Wright R-1820 Cyclone engines. 18 built by Keystone. Martin PM-1 Production derivative of PN-12. Two Wright R-1750 Cyclone engines. 27 built for US Navy by Martin. Martin PM-1B Export version of PM-1 for Brazil. Three built. Martin PM-2 Improved derivative of PM-1 with more powerful Wright R-1820 Cyclone engines and twin tails. 25 built. Operators Brazilian Naval Aviation United States Navy Specifications (PN-12) See also Boeing XPB Earl Schuyler Kleinhans References External links https://web.archive.org/web/20071013194609/http://bluejacket.com/usn-usmc_avi_image_vintage_g-z.htm#P http://www.cofe.ru/avia/N/N-31.htm http://www.history.navy.mil/branches/avchr3.htm Flying boats Naval Aircraft Factory PN01 P1N Biplanes Twin piston-engined tractor aircraft