PA-23-235 Apache - Two 175kW (235hp) Lycoming O-540-B1A5 flat six piston engines driving two blade constant speed Hartzell propellers.
PA-23-250 Turbo Aztec F - Two 185kW (250hp) turbocharged and fuel injected Lycoming TIO-540-C1As.
PA-23-235 - Max speed 325km/h (176kt), max cruising speed 307km/h (166kt). Initial rate of climb 1450ft/min. Service ceiling 17,200ft. Max range with no reserves 1907km (1030nm).
PA-23-250 Turbo - Max speed 408km/h (220kt), max cruising speed 390km/h (211kt), economical cruising speed 335km/h (181kt). Initial rate of climb 1470ft/min. Service ceiling 24,000ft. Range at max cruising speed 1797km (970nm), at economical cruising speed 2309km (1246nm).
Apache seats four. Aztec first model seats five, later Aztecs seat six.
Almost 7000 PA-23s built, comprising 2047 Apaches and 4930 Aztecs, including a small number of military sales.
Four seat light twins
The origins of the PA-23 Apache (one of the first widely available GA twins and Piper's first "Indian") and the larger and more powerful Aztec lie in the early postwar Twin Stinson design.
Piper acquired the assets of Consolidated Vultee's Stinson Aircraft division in 1948, and inherited a design study for a modern four place light twin. Piper left the design dormant for a few years until 1952 when it built a prototype aircraft, cn 23-01, based on the Stinson design. The low wing four seat twin was powered by 93kW (125hp) Lycoming O-290-D engines, had fabric covering, fixed undercarriage and a twin fin tail design.
Unsatisfactory flight trials led Piper to substantially redesign cn 23-01, introducing first more powerful 100kW (135hp) engines, then increasing power to (110kW) 150hp, metal construction, retractable undercarriage and a conventional tail unit. The redesigned twin flew for the first time on March 2 1952. Production deliveries began in March 1954.
The first variant was the PA-23-150 with some detail changes in subsequent model years before production switched to the more powerful PA-23-160 in late 1958. The Apache G and H introduced a third cabin window. A subsequent Apache development was the PA-23-235 Apache 235, a lower powered development of the PA-23-250 Aztec, introduced in 1962.
The Aztec is an enlarged and more powerful development of the Apache powered by two six cylinder 185kW (250hp) O-540s, and Aztecs were first delivered from early 1960. The Aztec B introduced a longer nose and seating for six, the Aztec C fuel injected engines, the optional Turbo Aztec C was turbocharged, while the Aztec D, E and F and corresponding turbo models introduced detail changes.
A military version for the US Navy was the UO-1, later renamed the U-11A. Except for radio, oxygen and propeller anti-icing equipment, this model was similar to the civil Aztec. Twenty were delivered in 1960. Some other air forces used Aztecs in small numbers.
A special version for the UK market with a gross weight of 2265kg (4995lb) instead of 2360kg (5200lb) was the PA-E23-250.
Production of the Aztec ceased in 1982.
Several Apache conversions with higher-powered engines, extended nose cone, fully enclosed wheel doors, square tipped rudder, etc were available as the Seguin Geronimo, the Miller Jet Profile and the Wilson Jet Profile. Some aircraft were only partly modified.
A floatplane modification of Aztecs adding also an additional door is offered by Melridge Aviation and Jobmaster Company as the Aztec Nomad.