The 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.

Design and development

thumb|right| PA-25-235 Pawnee C at the [[Celje Airport]]

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. 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.

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.

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.

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.

Variants

thumb|PA-25-235 Pawnee B towing a glider

thumb|The Swift Aerobatic Display Team at [[Kemble Airfield|Kemble Battle of Britain Weekend 2009. A Swift glider is performing continuous full rolls while being towed by a Pawnee]]

;AG-3

:Prototype built at Texas A&M University.

;PA-25-150 Pawnee

:Initial production version fitted with a Lycoming O-320 engine. Payload of powders or liquids.

;PA-25-235 Pawnee B

:Fitted with a Lycoming O-540-B2B5 six-cylinder engine. The Pawnee B featured a larger hopper and an increased payload of .

;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. Other differences include a belted propeller speed reduction unit.

;Laviasa PA-25 Puelche 235

: Improved version of Pawnee built by Latino Americana de Aviación in Argentina. Powered by Textron Lycoming O-540-B2C5.

;Laviasa PA-25 Puelche 260

: Powered by O-540-G2A5 engine.

|prime units?=imp

<!--

General characteristics

-->

|genhide=

|crew=1

|capacity= or powder

|length m=

|length ft=24

|length in=7

|span m=

|span ft=36

|span in=2

|height m=

|height ft=7

|height in=2

|wing area sqm=

|wing area sqft=183

|aspect ratio=7.15:1

|airfoil=USA 35B (modified)

|empty weight kg=

|empty weight lb=1488

|gross weight kg=

|max takeoff weight lb=2900

|fuel capacity=

<!--

Powerplant

-->

|eng1 number=1

|eng1 name=Lycoming O-540-B2B5

|eng1 type=air-cooled six-cylinder horizontally-opposed engine

|eng1 kw=<!-- prop engines -->

|eng1 hp=235<!-- prop engines -->

|prop blade number=2<!-- propeller aircraft -->

|prop name=McCauley 1A200/FA84 metal fixed-pitch propeller

|prop dia m=<!-- propeller aircraft -->

|prop dia ft=7<!-- propeller aircraft -->

|prop dia in=0<!-- propeller aircraft -->

<!--

Performance

-->

|perfhide=

|max speed kmh=

|max speed mph=110

|max speed kts=

|max speed note=at sea level

|cruise speed kmh=<!-- if max speed unknown -->

|cruise speed mph=100

|cruise speed note=(75% power)

|stall speed mph=61

|stall speed note=(flaps down)

|range km=

|range miles=300

|range note=(75% power, full fuel)

|ceiling m=

|ceiling ft=13000

|climb rate ms=

|climb rate ftmin=630

|more performance=*Take-off run to 50 ft (15 m):

  • Landing distance from 50 ft (15 m):

|avionics=

See also

Related development:

  • Texas A&M College AG-1
  • Gippsland Aeronautics PA-25-235/A9 'Fatman'
  • Piper PA-36 Pawnee Brave

Comparable aircraft:

  • Aero Boero 260AG
  • Air Tractor AT-300
  • Air Tractor AT-802
  • Ayres Thrush
  • CallAir A-9
  • Cessna 188 AgWagon
  • Embraer EMB-202 "Ipanema"
  • Grumman Ag Cat
  • PZL-106 Kruk
  • PZL-Mielec M-18 Dromader
  • Zlin Z-37 Čmelák

Notes

Bibliography

  • Green, William. Aircraft Handbook. London. Macdonald & Co. (Publishers) Ltd., 1964.
  • Peperell, Roger and Smith, Colin. Piper Aircraft and their forerunners Tonbridge, Kent, England Air-Britain 1987.
  • Taylor, John W. R. Jane's All the World's Aircraft 1962–63. London: Sampson Low, Marston & Company, Ltd., 1962.
  • PA-25 Pawnee fliegerszene.de