https://en.wikipedia.org/wiki/Piper_PA-25_Pawnee
The PA-25 Pawnee was an agricultural aircraft produced by Piper Aircraft between
1959 and 1981. It remains a widely used aircraft in agricultural spraying and is
also used as a tow plane, or tug, for launching gliders or for towing banners.
In 1988 the design rights and support responsibility were sold to Latino
Most agricultural aircraft before 1949 were converted military aircraft and it
was in that year that Fred Weick based at Texas A&M University designed a
dedicated agricultural aircraft the AG-1, the AG-1 first flew on 1 December
1950.
During 1953 Fred Weick was approached by Piper to become a consultant on the
agricultural version of the PA-18 the PA-18A, in particular to design and test a
distributor for dust and seeds. A few weeks later Piper sponsored Texas A&M
University to design a dedicated agricultural aircraft based on the AG-1 but to
use as many PA-18A and PA-22 components as possible, the resulting design the
AG-3 was smaller than the AG-1 and had a steel tube fuselage and was fabric
covered. The AG-3 was a single-seat low-wing monoplane with the wings braced to
the fuselage with struts, it had a conventional landing gear with a tailwheel
and was powered by a 135 hp engine. The single seat was placed high in the
fuselage to give the best visibility and an 800 lb-capacity hopper was fitted in
front of the cockpit.
The aircraft's flying tests were successful and in 1957 Weick was invited to
join Piper at Vero Beach and the AG-3 was renamed the PA-25 Pawnee. The engine
was upgraded to a 150 hp Lycoming O-320-A1A engine. Two pre-production aircraft
were built at Vero Beach in 1957 and production started at Lock Haven in May
1959.
In 1962 another prototype was built at Vero Beach with a 235 hp Lycoming
O-540-B2B5 engine and production aircraft were produced at Lock Haven from 1962.
In 1964 the Pawnee B was introduced with a larger hopper and improved dispersal
gear. The Pawnee C of 1967 was fitted with oleo shock-absorbers and other
improvements; also in 1967, a 260 hp variant was introduced.
Role
Agricultural aircraft
National origin
United States
Manufacturer
Piper Aircraft
Designer
Fred Weick
First flight
1957
Introduction
August 1959
Produced
1959-1981
Number built
5167
In 1962 another prototype was built at Vero Beach with a 235 hp Lycoming
O-540-B2B5 engine and production aircraft were produced at Lock Haven from 1962.
In 1964 the Pawnee B was introduced with a larger hopper and improved dispersal
gear. The Pawnee C of 1967 was fitted with oleo shock-absorbers and other
improvements; also in 1967, a 260 hp variant was introduced.
Early models of the Pawnee had a single fuel tank located between the
agricultural hopper and the engine. The National Transportation Safety Board
recommended to Piper Aircraft that the early model PA-25's with a fiberglass
fuel tank be retrofitted with a rubber fuel cell to minimize the chance of
catastrophic failure and fire resulting from a crash.
In 1974 the Pawnee D was introduced with the fuel tanks moved from the fuselage
to the wings, the 260 hp variant was also available with either a fixed pitch or
constant-speed propeller. Although still the same design as the "D", the 1980
and 1981 production aircraft were marketed as the Pawnee. The final production
aircraft was completed at Lock Haven on 22 March 1981, the last of 5,167
Pawnees.
A useful design aspect was the ability to carry a mechanic on a jump seat fitted
in the hopper to assist with operations at remote stations.
On April 15, 1988, Piper Aircraft, Inc. officially sold the PA-25 series
drawings, engineering data, parts inventory, tools, catalogs, and manuals. All
support of any nature became the responsibility of the new owners.
Specifications (PA-25-235 Pawnee)
General characteristics
Crew: One
Capacity: 150 US gal (568 l) or 1,500 lb (545 kg) of chemicals
Length: 24 ft 9 in (7.55 m)
Wingspan: 36 ft 2 in (11.02 m)
Height: 7 ft 2 in (2.19 m)
Empty: 1,457 lb (662 kg)
Loaded: 2,900 lb (1,317 kg)
Maximum takeoff: 2,900 lb (1,317 kg)
Powerplant: 1 x Lycoming O-540-B2B5, 235 hp (175 kW)
Performance
Maximum speed: 107 kts or 124 mph (188 km/h)
Range: 300 miles (500 km)
Service ceiling: 13,000 ft (3,963 m)
Rate of climb: 630 ft/min (192 m/min)(at MTOW)
Power/Mass: 0.0810 hp/lb (0.133 kW/kg)
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