The Piper PA-23, named Apache and later Aztec, is a four-to-six-seat twin-engined light aircraft aimed at the general aviation market. The United States Navy and military forces in other countries also used it in small numbers. Originally designed in the 1950s by the Stinson Aircraft Company, Piper Aircraft manufactured the Apache and a more powerful version, the Aztec, in the United States from the 1950s to the 1980s.
The same year, Piper produced an upgraded version with 250 hp (186 kW) Lycoming O-540 engines and a swept vertical tail as the PA-23-250, and named it Aztec. The first models came in a five-seat configuration in 1959.
In 1961 a longer nosed variant, the Aztec B, entered production. Later Aztecs were equipped with IO-540 fuel-injected engines and six-seat capacity, and remained in production until 1982. There were also turbocharged versions of the later models, which could fly at higher altitude. The United States Navy acquired 20 Aztecs, designating them UO-1, which changed to U-11A when unified designations were adopted in 1962.
In 1974, Piper produced a single experimental PA-41P Pressurized Aztec concept. This concept was short-lived, however, as the aspects of the Aztec that made it so popular for its spacious interior and ability to haul large loads did not lend themselves well to supporting the sealed pressure vessel required for a pressurized aircraft. The project was scrapped, and the one pressurized Aztec produced, N9941P, was donated to Mississippi State University, where it was used for testing purposes.
In 2000, N9941P was donated to the Piper Aviation Museum in Lock Haven, Pennsylvania, on condition that it never be flown again. It is now there on display. - Wikipedia