Piper PA-23 Apache / PA-23 Aztec / UO-1 / U-11

It all began in 1952 with the introduction of the Twin-Stinson, the first Piper of Stinson lineage to be produced since the Piper/Stinson Flying Station Wagon. It was powered by twin 125-hp Lycoming engines. The following year Piper introduced the PA-23 Apache, a vast improvement on the Twin-Stinson concept.The Apache featured a conventional single rudder tail unit rather than the Twin-Stinson’s twin-tail configuration, and power was boosted with the use of 150-hp Lycomings. The new Piper also utilized all-metal construction and retractable landing gear.

On 2 March 1952 Piper flew the prototype of a new twin-engine aircraft which it then identified as the Piper PA-23 Twin-Stinson. A cantilever low-wing monoplane of all-metal construction, it had a tailplane set high on the fuselage and mounting endplate fins and rudders, retractable tricycle landing gear and an enclosed cabin seating four in two pairs, and was powered by two 112kW Avco Lycoming O-320 flat-four engines in wing-mounted nacelles. The tail unit was very soon replaced by a conventional tailplane with centrally mounted single fin and rudder, and it was in this form that it entered production in early 1954 as the PA-23 Apache, later designated PA-23 Apache 150.

Powered by two Lycoming O-320 engines, each of 150 h.p. with Hartzell constant-speed airscrews, the Apache has comprehensive instruments and radio equipment included to remove the limitation of "daylight, V.F.R. only" flying, and the selling price of the new machine was $32,500, or approximately £11,600, in 1954.

Maximum all-up weight of the Apache is 3,500 lb which, with full tanks, four passengers, full instrumentation aria radio, enables 198 lb of baggage or extra equipment to be carried. Maximum sea-level cruising speed is 160 m.p.h. Single-engined ceiling at top weight is 5,000 ft, and at 3,100 lb is 8,000 ft.

The aircraft is of all-metal construction, and has an empty weight (completely equipped) of 2,170 lb. The "Custom" model is fitted with the three radio installations shown in the cockpit photograph; an autopilot can be fitted. The baggage compartment behind the cabin has a volume of 25 cu ft, and the rear passenger seats can be easily removed to increase the available cargo space to 80 cu ft.

The dual controls are conventional, with toe brakes on the left rudder pedals, and with connections to the steerable nosewheel. Rudder and elevator trim controls are located centrally in the cabin roof. The "Electrol" tricycle landing gear is hydraulically retractable and is fitted with Goodrich wheels, tyres and brakes. Two 36-gallon rubber fuel tanks are installed in the wing, outboard of the engines. The span of the Apache is 37ft; length 27ft lin; and wing area 204 sq ft.

The Apache achieved FAA 1A10 certification on January 29, 1954, with Lycoming 150hp. This ended up covering all PA-23, PA-23-160, and PA-23-250 27-1 to 27-1999 and 27-2505 to 27-8154030.

In 1958, O-320-B 160-hp engines were added as the PA-23 Apache 160, and with some interior revisions so that it was classed as a four/ five-seat aircraft (816 built), and in 1963, the 175kW / 235-hp Lycoming O-540-B1A5 became the standard powerplant to meet requirements for better single-engine performance (119 built). This later model was the first to sport swept tail surfaces and was quite similar to the Aztec of the same vintage, except for the Apache’s smaller engines and shorter nose.

 

The optional fifth seat became available in 1956, retrofitable to earlier models, though baggage capacity was reduced from 200 lbs to 30 lbs when the seat was occupied, and two 18 USG aux tanks in the outboard wings were installed. Introduced in 1958 were the 160 hp Lycomings along with an increase in MTOW from 3500 lbs to 3800 lbs.

 

The 1960 Apache G began the third side window. Some 170 of the 1961 Apache H model were built.

 

From 1962 to 1965, built 117 Apache 235s. More than 2000 150- to 160-hp Apaches were built between 1954 and 1962 until production was replaced by the Twin Commanche (introduced in 1963).

Piper’s 1964 Aztec had streamlined nacelles, flush wing flaps and fully enclosed wheel doors raising the max cruise to 208 mph. Lycoming 250 hp engines have fuel injection and lightweight Hartzell props. The price was $54,990.

The type continued in production as the Apache until 1965, by which time 2,166 had been built, including 1,231 examples of the first production version.

With sales of the Apache 235 declining, Piper developed an improved version of this aircraft in 1960 which introduced a 250 hp / 186kW O-540 engine and provided six-seat capacity. The Aztec introduced a longer fuselage, longer nose, squared tail, and 5-6 seats instead of the Apache’s four.

This entered production under the designation PA-23-250 Aztec in 1959-60, the US Navy acquiring 20 of these aircraft for use in a utility role, designating them UO-1, changed to U-11A in 1962. The Aztec was built until early 1982 when production was suspended. In final production form the type had the designation PA-23-250 Aztec F, and was available also as the generally similar PA-23T-250 Turbo Aztec F which differed by having Avco Lycoming TIO-540 engines with a Garrett turbo-charging system. The first F model, introduced in 1976, offered optional fuel capacity increase.

Both Apache and Aztec were available until the Apache line was dropped. A total of 2047 were built from 1954 to 1962.

Gallery

1954 Piper Apache 150
Engines: 2 x Lycoming O-320-A1A, 150 hp
TBO: 2200 hr
Fuel type: 100LL
Props: Hartzell HC-82VL-2C, 2 blade CS, 72 in..
Landing gear: hydraulic Tri/Retr.
Max ramp weight: 3800lb
Gross weight: 3800 lb
Landing weight: 3800 lb
Empty weight, std: 2215 lb
Useful load, std: 1585 lb
Payload, full std. fuel: 1153 lb
Usable fuel: 72 USG
Optional fuel: 108 USG
Oil capacity: 8 qt
Wingspan: 37 ft
Overall length: 27 ft. 1 in
Height: 9 ft. 6 in
Wing area: 208 sq. ft
Wing loading: 12.7 lbs./sq. ft
Power loading: 12.7 lbs./hp
Wheel base: 7 ft. 4 in
Wheel track: 11 ft. 4 in
Wheel size: 6.00 x 6 in
Seating capacity: 4 std, 5 opt
Cabin doors: 1
Cabin width: 48 in
Cabin height: 50 in
Baggage capacity: 200 lb /25 cu. ft
Maximum speed: 180 mph
Cruise speed 75% power @ 6,000 ft: 146 kt / 170 mph
Cruise speed 65% power @ 9,000 ft: 139 kt / 162 mph
Cruise speed 55% power @ 12,000 ft: 128 kt
Range at 75% pwr no reserve (72 USgal): 620 sm
Range at 65% pwr no reserve (72 USgal): 710 s.m
Maximum range no reserve (72 USgal): 840 sm
Fuel consumption 75% power: 18.0 USgph
Fuel consumption 65% power: 16.0 USgph
Fuel consumption 55% power: 14.0 USgph
Vs: 59 kt
Vso: 51 kt
Stall speed, gear and flaps up: 66mph. Stall speed, gear and flaps down: 59 mph
Best rate of climb (SL): 1150 fpm
Best rate of climb, 8000 ft: 600 fpm
Service ceiling: 15,500 ft
Single-engine absolute ceiling: 6750 ft
Rate of climb, SE SL: 240 fpm
Takeoff ground roll: 1290 ft
Takeoff over 50-ft. obstacle (ft.): 1600 ft
Landing ground roll: 750 ft
Landing over 50-ft. obstacle: 1360 ft

PA23-160 Apache
Engines: 2 x Lycoming O-320, 160 hp.
Gross wt: 3,800 lb
Empty wt. 2,280 lb
Total fuel cap: 108 USG
Max speed 3,000 ft: 152 kt / 183 mph
Vmc: 70 kt
Initial climb rate 1,260 fpm
Best SE climb speed: 83kt
SE ceiling: 5,500 ft
Cruise 23x23: 130 kt / 173 mph
Stall 61 mph
Range 1,260 sm
Ceiling 17,000 ft
Takeoff run 1,190 ft
Landing roll 750 ft
Seats 4-5