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Piper PA-25 Pawnee
View on WikipediaThe PA-25 Pawnee is 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 Americana de Aviación of Argentina.
Key Information
Design and development
[edit]
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.[1]
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.[1] 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 which was fabric covered.[1] 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.[1] 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.[1]
The AG-3 made its maiden flight in November 1954.[2] 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.[1] Two pre-production aircraft were built at Vero Beach in 1957 and production started at Lock Haven, Pennsylvania, in May 1959.[1]
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.[1] 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.[1]
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.[3]
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.[1] Although still the same design as the "D", the 1980 and 1981 production aircraft were marketed as the Pawnee.[1] The final production aircraft was completed at Lock Haven on 22 March 1981, the last of 5,167 Pawnees.[1]
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.[4]
On April 15, 1988, Piper Aircraft, Inc. officially sold the PA-25 series aircraft to Latino Americana de Aviación S.A in Argentina. The sale included all drawings, engineering data, parts inventory, tools, catalogs, and manuals. All support of any nature became the responsibility of the new owners.[5]
In 2019, Australia's Civil Aviation Safety Authority formally approved the issuing to eTugs of Certificates of Airworthiness in the Limited category for the purpose of glider towing. An etug is a PA-25 where the Lycoming engine has been replaced with a General Motors LS automotive engine. The advantages for glider towing, compared to a Lycoming powered PA-25, include a greater rate of climb, reduced fuel consumption, the elimination of shock cooling (since the LS is water-cooled rather than air-cooled) and a less costly maintenance regime.[6][7]
Variants
[edit]

- AG-3
- Prototype built at Texas A&M University.
- PA-25-150 Pawnee
- Initial production version fitted with a 150 hp (110 kW) Lycoming O-320 engine. Payload of 800 lb (360 kg) powders or 145 US gal (121 imp gal; 550 L) liquids.[8]
- PA-25-235 Pawnee B
- Fitted with a 235 hp (175 kW) Lycoming O-540-B2B5 six-cylinder engine. The Pawnee B featured a larger hopper and an increased payload of 1,200 lb (540 kg).[9]
- PA-25-235 and PA-25-260 Pawnee C
- The Pawnee C was an upgraded version of the 'B' model and was available with a 235hp or a 260hp high compression version of the O-540 engine and either a fixed pitch or constant speed propeller. The fuselage of the Pawnee C featured a quickly detachable 'turtledeck' panel to ease the rinsing out of spilt corrosive agents from the fuselage structure and to facilitate servicing and inspection of components housed in the rear section of the fuselage.
- PA-25-235 and PA-25-260 Pawnee D
- The Pawnee D was also powered by a Lycoming O-540 of 260hp but featured fuel tanks fitted in the outer wings and metal covered ailerons and flaps. From 1980 it was known as the PA-25-235 Pawnee.
- eTug
- A modified PA-25 powered by a General Motors LS automotive engine driving a three-bladed propeller.[10] Other differences include a belted propeller speed reduction unit.[citation needed]
- Laviasa PA-25 Puelche 235
- Improved version of Pawnee built by Latino Americana de Aviación in Argentina. Powered by 235 hp (175 kW) Textron Lycoming O-540-B2C5.[11]
- Laviasa PA-25 Puelche 260
- Powered by 260 hp (190 kW) O-540-G2A5 engine.[11]
- Laviasa Puelche Trainer
- Two seat trainer version of Puelche 235 with side-by-side seating.[11]
Accidents and incidents
[edit]- 9 August 1974 a crop-spraying Pawnee was involved in a fatal mid-air collision in Norfolk, UK with a Royal Air Force McDonnell Douglas F-4M Phantom FGR.2.
Specifications (PA-25-235 Pawnee B)
[edit]
Data from Jane's All the World's Aircraft 1965–66 [12]
General characteristics
- Crew: 1
- Capacity: 150 US gal (120 imp gal; 570 L) or 1,200 lb (540 kg) powder
- Length: 24 ft 7 in (7.49 m)
- Wingspan: 36 ft 2 in (11.02 m)
- Height: 7 ft 2 in (2.18 m)
- Wing area: 183 sq ft (17.0 m2)
- Aspect ratio: 7.15:1
- Airfoil: USA 35B (modified)
- Empty weight: 1,488 lb (675 kg)
- Max takeoff weight: 2,900 lb (1,315 kg)
- Fuel capacity: 40 US gal (33 imp gal; 150 L)
- Powerplant: 1 × Lycoming O-540-B2B5 air-cooled six-cylinder horizontally-opposed engine, 235 hp (175 kW)
- Propellers: 2-bladed McCauley 1A200/FA84 metal fixed-pitch propeller, 7 ft 0 in (2.13 m) diameter
Performance
- Maximum speed: 110 mph (180 km/h, 96 kn) at sea level
- Cruise speed: 100 mph (160 km/h, 87 kn) (75% power)
- Stall speed: 61 mph (98 km/h, 53 kn) (flaps down)
- Range: 300 mi (480 km, 260 nmi) (75% power, full fuel)
- Service ceiling: 13,000 ft (4,000 m)
- Rate of climb: 630 ft/min (3.2 m/s)
- Take-off run to 50 ft (15 m): 1,370 ft (420 m)
- Landing distance from 50 ft (15 m): 1,350 ft (410 m)
See also
[edit]Related development:
Comparable aircraft:
Notes
[edit]- ^ a b c d e f g h i j k l Peperell/Smith 1987, pp.113-120
- ^ Bridgman 1958, p. 380.
- ^ National Transportation Safety Board A-87-99, July 22, 1987
- ^ Macdonald 1964, p. 137
- ^ Piper Service Spares Letter No. 413, May 8, 1988
- ^ Infrastructure. "CASA EX53/14 - Exemption — for certain aircraft to tow gliders". www.legislation.gov.au. Retrieved 2019-11-09.
- ^ "Gliding Australia issue 49" (PDF). September 2019. Archived from the original (PDF) on 2019-11-09. Retrieved 2019-11-09.
- ^ Taylor 1962, p. 264.
- ^ "Newsreel: New Piper Pawnee". Flying. Vol. 70, no. 5. May 1962. p. 69.
- ^ "eTug". Glider Club of Victoria. Retrieved November 9, 2019.
- ^ a b c Jackson 2008, p. 2
- ^ Taylor 1965, p. 290
Bibliography
[edit]- Bridgman, Leonard (1958). Jane's All the World's Aircraft 1958–59. London: Sampson Low, Marston & Company, Ltd.
- Goodrum, Alastair (January–February 2004). "Down Range: Losses over the Wash in the 1960s and 1970s". Air Enthusiast (109): 12–17. ISSN 0143-5450.
- Green, William. Aircraft Handbook. London. Macdonald & Co. (Publishers) Ltd., 1964.
- Jackson, Paul, ed. (2008). Jane's All the World's Aircraft 208–2009. Coulsdon, UK: Jane's Information Group. ISBN 978-0-7106-28374.
- Peperell, Roger and Smith, Colin. Piper Aircraft and their forerunners Tonbridge, Kent, England Air-Britain 1987. ISBN 0 85130 149 5
- Taylor, John W. R. Jane's All the World's Aircraft 1962–63. London: Sampson Low, Marston & Company, Ltd., 1962.
- Taylor, John W. R. (1965). Jane's All the World's Aircraft 1965–66. London: Sampson Low, Marston & Company, Ltd.
External links
[edit]Piper PA-25 Pawnee
View on GrokipediaDesign and development
Origins and early prototypes
The development of the Piper PA-25 Pawnee originated from efforts to create a dedicated agricultural aircraft tailored to the needs of crop dusting and spraying operations. In 1949, aeronautical engineer Fred Weick, working at Texas A&M University in collaboration with the university's agricultural research program and the Civil Aeronautics Administration, began designing the AG-1 prototype to address safety and efficiency issues in early aerial application aircraft. This single-seat, low-wing monoplane incorporated features like a rearward-shifted cockpit for better visibility over the spray load and a chemical hopper positioned forward for balance. The AG-1 made its first flight on December 1, 1950, powered by a 225 hp Continental E-225 engine, and demonstrated improved stability during low-altitude maneuvers essential for agricultural work.[5][6] Building on the AG-1's success, Weick and his team advanced the design through the AG-2 and AG-3 prototypes, with the latter involving direct input from Piper Aircraft for potential production. The AG-3, constructed largely from Piper-supplied components, featured refinements such as enhanced structural durability for rough-field operations. It achieved its first flight in November 1954 and underwent extensive testing by hundreds of farmers to validate its agricultural performance. Following successful evaluations in 1956, Piper hired Weick and acquired the design rights, redesignating it as the PA-25 prototype. Two pre-production PA-25 aircraft were built at Piper's Vero Beach facility in 1957, equipped with a 150 hp Lycoming O-320-A1A engine, and the design received its type certificate that year at a gross weight of 2,300 pounds.[7][8][5] Key early design elements emphasized the Pawnee's agricultural specialization, including a fixed tailwheel landing gear for operations on unprepared airstrips and a low-wing configuration with struts for inherent stability at low speeds and altitudes during spraying. The forward hopper had a capacity of 100 US gallons (approximately 800 pounds of liquid or dry chemicals), allowing efficient payload delivery without excessive weight shifts. Production commenced in May 1959 at Piper's Lock Haven, Pennsylvania plant, with the aircraft publicly introduced in August of that year. The name "Pawnee" was selected in line with Piper's tradition of honoring Native American tribes, drawing from the Pawnee people's historical reputation for endurance and resilience to symbolize the aircraft's rugged capabilities.[8][4][9][10]Production models and improvements
The production of the Piper PA-25 Pawnee commenced in 1959 at Piper Aircraft's facility in Lock Haven, Pennsylvania, and spanned until March 22, 1981, resulting in a total of 5,167 units built.[11][3] This manufacturing run marked Piper's entry into dedicated agricultural aviation, with iterative upgrades focused on enhancing power, payload, and operational reliability for chemical dispersal tasks. In 1962, Piper introduced the Model B, designated as the PA-25-235, which replaced the initial 150 hp version with a more capable 235 hp Lycoming O-540 engine.[8][2] This model featured an enlarged hopper capacity of 150 US gallons (or 1,200 lb payload), the addition of wing-mounted fuel tanks for improved range, and a redesigned bottom engine cowling with side exhaust outlets to optimize airflow and reduce exposure to corrosive chemicals.[1][11] These changes bolstered the aircraft's durability in harsh agricultural environments, where the steel-tube fuselage was already reinforced to withstand chemical splatter and abrasion.[8] The Model C, produced from 1967, built on these advancements with optional 260 hp Lycoming O-540 variants for greater performance in demanding conditions.[8] Key improvements included a switch to metal fixed-pitch propellers for better resistance to wear, enhanced cockpit visibility through redesigned glazing, and the incorporation of oleo shock absorbers on the landing gear to improve rough-field handling.[12][1] By 1974, the Model D (PA-25-235D and PA-25-260D) further refined the design with optimized spraying systems for more precise chemical distribution and reduced drift, alongside hopper capacity of 150 US gallons (1,200 lb) in liquid configurations. Additional durability enhancements, such as corrosion-resistant coatings on the airframe and refined cowling seals, addressed long-term exposure to fertilizers and pesticides.[1][8] Piper's direct involvement ended with the cessation of production in 1981, though the design rights were sold in 1998 to Lavia Argentina S.A. (Laviasa) in Argentina, transferring support responsibilities.[3][13]Operational history
Agricultural applications
The Piper PA-25 Pawnee served primarily as a single-seat aerial applicator for dispensing pesticides, fertilizers, and seeds in agricultural operations.[5] Its design incorporated a forward-mounted hopper with capacities ranging from 800 pounds in early models to 1,200 pounds in later variants like the PA-25-235, enabling efficient loading and distribution of chemicals or dry materials.[5][8] This configuration allowed pilots to perform targeted applications over vast fields, marking it as one of the first purpose-built aircraft for such tasks following its certification in 1959.[14] From the 1960s onward, the Pawnee saw widespread deployment in U.S. agriculture, supporting the expansion of aerial application services that treated approximately 127 million acres annually by the late 20th century.[5] Internationally, it gained popularity in regions like Australia and New Zealand during the 1960s and 1970s for crop protection efforts, where operators valued its rugged construction for demanding environments.[15][16] In South America, particularly Argentina, licensed production and modifications by companies such as Laviasa extended its use into ongoing agricultural spraying programs.[13] Over its production run through 1981, more than 5,000 units were built, solidifying its role in enhancing large-scale farming efficiency worldwide.[8] Key operational features included the ability to fly at low altitudes as low as 5 feet above the ground for precise coverage, with climb rates supporting safe turns at 60-70 mph after passes.[8] Wing-mounted boom systems facilitated even distribution of sprays or dusts, adaptable for various applications such as insecticide dispersal in cotton fields to control pests like the boll weevil.[8] These attributes made it suitable for diverse crops, contributing to its longevity in operations despite the evolution of more powerful successors.[17] The Pawnee's adoption significantly reduced manual labor in spraying tasks, allowing farmers to cover areas in hours that would take days by ground methods and minimizing crop damage from equipment.[8] By enabling timely interventions in pest control and fertilization, it boosted yields in intensive farming regions, with U.S. aerial applicators reporting substantial cost savings through higher throughput.[5] Its economic influence persisted into the 1980s, as many units remained in service, underscoring the aircraft's impact on modern agricultural productivity.[15]Glider towing and other uses
The Piper PA-25 Pawnee began seeing conversions for glider towing in the early 1960s, shortly after its introduction as an agricultural aircraft, with early examples like serial number 25-438—produced in 1960 and registered in 1961—adapted for this role after initial crop-dusting service.[18] The 235 hp variant, equipped with a Lycoming O-540 engine, proved particularly effective due to its high power-to-weight ratio and robust construction, allowing it to serve as a reliable tug for launching gliders.[19] This model can tow gliders weighing up to approximately 1,500 pounds—such as heavy two-seat fiberglass types—at typical speeds of 70-80 mph, facilitating safe and efficient ascents for both single- and two-place sailplanes.[20][21] In addition to glider operations, the Pawnee has been widely utilized for banner towing and aerial advertising in recreational and promotional contexts, capitalizing on its exceptional stability, short takeoff and landing performance, and low stall speed of 53 KIAS.[22] These attributes enable precise low-speed maneuvers essential for picking up and displaying banners over events, beaches, and urban areas, while the aircraft's forward visibility aids pilot situational awareness during extended tows.[22] Its continued employment in this capacity was evident as recently as October 2025, when a Pawnee towed advertising banners during parades in Minnesota.[23] The Pawnee has also found limited application in pilot training programs, particularly for instruction in low-level flight and rough-field operations, where its taildragger landing gear and rugged agricultural heritage provide valuable experience in regions without access to specialized trainers.[24] Agricultural aviation schools, such as Battlefords Airspray in Canada, incorporate solo flights in the single-seat Pawnee to build skills in handling high-power, low-speed scenarios akin to real-world spraying or towing tasks.[24] As of 2025, the PA-25 Pawnee remains in active service with glider clubs across the United States, Australia, and Europe, where its proven reliability supports ongoing towing operations despite the aircraft's age.[25] Over 5,000 Pawnees were produced between 1959 and 1981, and numerous airframes continue to operate in these non-agricultural roles, including at facilities like Sandhill Soaring Club in Michigan and Melbourne Gliding Club in Victoria.[1][20][19]Variants
Piper-manufactured variants
The Piper PA-25 Pawnee was manufactured in a series of variants by Piper Aircraft, each featuring progressive enhancements in power, capacity, and durability to meet evolving agricultural demands. All models utilized Lycoming O-series engines and were certified under FAA Type Certificate 2A8 or 2A10 for restricted category operations, with options for normal category use in non-agricultural roles such as glider towing. Key differences centered on engine output from the O-320 to O-540 series, hopper capacities ranging from 800 lb to 1,200 lb payloads, fuel system relocation to the wings for better balance, and airframe refinements for corrosion resistance and crash protection. The initial variant, the PA-25-150 Pawnee, entered production in 1959 as the first certified model, powered by a 150 hp Lycoming O-320-A1A engine driving a fixed-pitch McCauley or Sensenich propeller. It featured a 20 cubic foot hopper rated for 800 lb of dry chemicals or 145 US gallons of liquid, with 40 gallons of fuel in a fuselage tank aft of the hopper, and a gross weight of 2,300 lb; serial numbers ranged from 25-1 to 25-731, with approximately 731 units built.[26][2] This model emphasized simplicity and low operating costs for small-scale spraying, with minor airframe tweaks including a welded steel-tube fuselage and fabric-covered Super Cub-style wings for durability in rough-field operations. Introduced in 1962, the PA-25-235 Pawnee B represented a major upgrade with a 235 hp Lycoming O-540-B2B5 or -B2C5 engine and a larger two-blade McCauley constant-speed propeller, increasing gross weight to 2,900 lb and hopper capacity to 1,200 lb or 150 US gallons. Fuel tanks were relocated to the wings (36-42 gallons total) to improve weight distribution and safety, while enhanced dispersal systems and ventilation addressed pilot comfort in chemical environments; over 1,186 units were produced through 1967, making it the most prolific variant. These changes boosted payload efficiency and climb performance, enabling broader crop coverage without sacrificing the original's rugged design.[27] The PA-25-235/260 Pawnee C, launched in 1967, built on the B model with optional 260 hp Lycoming O-540-G1A5 or -G2A5 engines paired with a three-blade Hartzell or McCauley propeller for better low-speed handling, alongside improved corrosion-resistant coatings on the metal spar wings and fuselage to extend service life in humid, chemical-exposed conditions. It retained the 1,200 lb hopper and wing fuel setup but incorporated refined avionics mounts for basic instrumentation; approximately 1,758 units were built until 1974, with serial numbers overlapping later 235 models from 25-4415 onward. This variant prioritized longevity and versatility, supporting both agricultural and utility roles with a useful load approaching 1,400 lb. The final Piper-produced model, the PA-25-235/260 Pawnee D, debuted in 1974 as a refined iteration with the same 235/260 hp O-540 engine options and propellers, but featured the 150 US gallon hopper capacity and updated avionics compatibility for modern radios and navigation aids. Airframe tweaks included stronger bracing and optional double tail wires for stability, maintaining the 2,900 lb gross weight; about 800 units were completed by 1981, with serial numbers up to 25-8156024. These enhancements focused on operational efficiency and regulatory compliance, solidifying the Pawnee's role in precision agriculture before production shifted to aftermarket licensees.[28] In total, Piper produced over 5,000 PA-25 Pawnees across all variants from 1959 to 1981.[4]Post-Piper and modified variants
Following the cessation of production by Piper Aircraft in 1981, the type certificate for the PA-25 was acquired by LAVIA Argentina S.A. in 1998, enabling licensed manufacturing in Mendoza, Argentina, under the designation PA-25 Puelche 235/260.[13] These variants retain the core design of the original Pawnee but incorporate local adaptations, such as gull wingtips and laminar flow landing gear, to enhance performance in agricultural roles.[29] The Puelche 235 is powered by a 235 hp Lycoming O-540 engine with fixed-pitch propeller options, while the Puelche 260 uses a 260 hp version, often with constant-speed propellers, supporting applications like spraying, seeding, and fire detection.[30] LAVIA introduced modifications in later models, such as the Puelche III, featuring an increased wingspan and higher payload capacity to optimize operations in high-altitude environments with low temperatures and humidity, common in Andean regions.[31] Production of these licensed variants continues as of 2025, with FAA and ANAC certifications ensuring compatibility with global standards.[13] A dedicated two-seat training variant, the LAVIA Puelche Trainer (also known as Biplaza Puelche), was developed with tandem seating and dual controls to facilitate pilot instruction in agricultural aviation and other specialized tasks.[32] Powered by the 235 hp Lycoming O-540-B4B5 engine and equipped with a 53-gallon fuel tank, it supports training, glider towing, and patrol duties in South American flight schools and operations.[33] In 2019, Australia's Civil Aviation Safety Authority (CASA) approved the eTug conversion for PA-25 Pawnees used in glider towing, involving replacement of the original Lycoming O-540 engine with a General Motors LS1 V8 automotive engine rated at approximately 300 hp, coupled via a propeller speed reduction unit.[34] This modification reduces overall aircraft weight compared to the stock piston engine while providing 60% greater static thrust, enabling more efficient launches—such as 12 two-seaters or 15 single-seaters per engine hour—and improved rapid descent capabilities.[35] Additionally, the eTug uses mogas fuel, eliminating lead emissions associated with avgas and supporting environmental goals in towing operations.[34]Specifications
General characteristics
The Piper PA-25-235 Pawnee is a single-seat agricultural aircraft designed for low-level operations, featuring a braced low-wing monoplane configuration with fixed conventional landing gear.[26] Its structure emphasizes durability for rough-field use, with a welded steel-tube fuselage covered in fabric and fabric-covered wings incorporating metal ailerons and flaps.[36] The design incorporates components from other Piper models, such as Super Cub wings and PA-22 tail surfaces, to facilitate production efficiency.[26] Key physical and weight specifications for the PA-25-235 are summarized below:| Characteristic | Specification |
|---|---|
| Crew | 1 pilot |
| Length | 24 ft 9 in (7.55 m) |
| Wingspan | 36 ft 2 in (11.02 m) |
| Height | 7 ft 2 in (2.18 m) |
| Wing area | 183 sq ft (17.0 m²) |
| Empty weight | 1,523 lb (691 kg) |
| Max takeoff weight | 2,900 lb (1,315 kg) |
| Fuel capacity | 38 US gal (144 L; 32 imp gal) |
| Payload (hopper) | 1,200 lb (544 kg) |
Performance
The Piper PA-25-235 Pawnee delivers performance tailored for agricultural and utility roles, emphasizing stable low-speed handling and efficient short-field operations at typical mission weights around 2,900 lb.[37]| Parameter | Value | Conditions/Notes |
|---|---|---|
| Maximum speed | 110 mph | At sea level[37] |
| Cruise speed | 95 mph | 75% power[37] |
| Stall speed | 50 mph | Flaps down[37] |
| Range | 300 mi | With full fuel (36 gal usable)[37] |
| Service ceiling | 13,000 ft | Standard day[37] |
| Rate of climb | 440–500 ft/min | Sea level, gross weight, depending on propeller[2] |
| Takeoff distance | 500 ft | Over 50 ft obstacle, sea level, standard day[37] |
| Landing distance | 600 ft | Over 50 ft obstacle, sea level, standard day[37] |
| Fuel consumption | 15 gal/hr | At cruise power[37] |
| Endurance | Approx. 2.5 hours | For typical agricultural missions with hopper load[37] |