Piper Aztec

The Piper PA-23, named Apache and later Aztec, was the first twin-engine aircraft built by Piper Aircraft.

Originally to be named the "Twin-Stinson" and designed as a four-seater low-wing all-metal monoplane, the prototype first flew 2 March 1952. It was renamed to "Apache 150" when it entered production in 1954; 1,231 were built. In 1958, the Apache 160 was produced by upgrading the engines to 160 hp (119 kW), and 816 were built before being superseded by the Apache 235, which went to 235 hp (175 kW) engines and swept tail surfaces (119 built).

Declining sales of the Apache prompted the redesign dubbed PA-23-250 Aztec, with 250 hp (186 kW) O-540 engines and six-seat capacity, which became available in 1959 and continued in production until 1982.

The US Navy acquired 20 Aztecs, designating them UO-1, which changed to U-11A when unified designations were adopted in 1962.