Piper PA-25 Pawnee

{{Short description|American agricultural aircraft}} {{Infobox aircraft | name = PA-25 Pawnee | image = File:Piper PA25-235 Pawnee D ‘G-BFPR’.jpg | caption = PA-25 Pawnee | type = [[Agricultural aircraft]] [[Towplane]] | national_origin = United States | manufacturer = [[Piper Aircraft]] | designer = [[Fred Weick]] | first_flight = [[1957 in aviation|1957]] | introduction = August 1959 | retired = | status = | primary_user = | produced = 1959-1981 | number_built = 5,167{{cn|date=September 2023}} | developed_from = | variants = }}

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 [[Glider aircraft|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== [[File:Letalisce Celje 2007-07 002.jpg|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 [[Texas A&M College Ag-1|AG-1]]. The AG-1 first flew on 1 December 1950.<ref name="ab">Peperell/Smith 1987, pp.113-120</ref>

During 1953, Fred Weick was approached by Piper to become a consultant on the agricultural version of the [[Piper PA-18 Super Cub|PA-18]], the PA-18A, in particular to design and test a distributor for dust and seeds.<ref name="ab" /> 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.<ref name="ab" /> 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.<ref name="ab" /> 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.<ref name="ab" />

The AG-3 made its maiden flight in November 1954.<ref>Bridgman 1958, p. 380.</ref> 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.<ref name="ab" /> Two pre-production aircraft were built at Vero Beach in 1957 and production started at [[Lock Haven, Pennsylvania]], in May 1959.<ref name="ab" />

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.<ref name="ab" /> 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.<ref name="ab" />

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.<ref>[[National Transportation Safety Board]] A-87-99, July 22, 1987</ref>

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.<ref name="ab" /> Although still the same design as the "D", the 1980 and 1981 production aircraft were marketed as the Pawnee.<ref name="ab" /> The final production aircraft was completed at Lock Haven on 22 March 1981, the last of 5,167 Pawnees.<ref name="ab" />

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.<ref name="Macdonald">Macdonald 1964, p. 137</ref>

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.<ref name="psp">Piper Service Spares Letter No. 413, May 8, 1988</ref>

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 based GM small-block engine|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.<ref>{{Cite web|url=http://www.legislation.gov.au/Details/F2014L00974/Explanatory%20Statement/Text|title=CASA EX53/14 - Exemption — for certain aircraft to tow gliders|last=Infrastructure|website=www.legislation.gov.au|language=en|access-date=2019-11-09}}</ref><ref>{{Cite web|url=http://www.glidingaustralia.org/mag/GA49.pdf|title=Gliding Australia issue 49|date=September 2019|access-date=2019-11-09|archive-date=2019-11-09|archive-url=https://web.archive.org/web/20191109040013/http://www.glidingaustralia.org/mag/GA49.pdf|url-status=dead}}</ref>

==Variants== [[File:piper pawnee pa25 glider-towing at kemble arp.jpg|thumb|PA-25-235 Pawnee B towing a glider]] [[File:swift aerobatic display team at kemble arp.jpg|thumb|The Swift Aerobatic Display Team at [[Kemble Airfield|Kemble Battle of Britain Weekend]] 2009. A [[Swift S-1|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 {{convert|150|hp|kW|abbr=on}} [[Lycoming O-320]] engine. Payload of {{convert|800|lb|kg|abbr=on}} powders or {{convert|145|USgal|impgal L|abbr=on}} liquids.<ref name="jawa62p264">Taylor 1962, p. 264.</ref> ;PA-25-235 Pawnee B :Fitted with a {{convert|235|hp|kW|abbr=on}} [[Lycoming O-540|Lycoming O-540-B2B5]] six-cylinder engine. The Pawnee B featured a larger hopper and an increased payload of {{convert|1200|lb|kg|abbr=on}}.<ref>{{cite magazine|title=Newsreel: New Piper Pawnee |magazine=[[Flying (magazine)|Flying]]|date=May 1962|volume=70|number=5|page=69}}</ref> ;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 [[Compression ratio|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 based GM small-block engine|LS]] automotive engine driving a three-bladed propeller.<ref>{{cite web |title=eTug |publisher=Glider Club of Victoria |url=https://www.glidingclub.org.au/members-only/aircraft/etug/ |access-date=November 9, 2019 |archive-date=March 28, 2023 |archive-url=https://web.archive.org/web/20230328000128/https://glidingclub.org.au/members-only/aircraft/etug/ |url-status=dead }}</ref> Other differences include a belted [[propeller speed reduction unit]].{{cn|date=November 2019}} ;Laviasa PA-25 Puelche 235 : Improved version of Pawnee built by Latino Americana de Aviación in Argentina. Powered by {{convert|235|hp|kW|abbr=on}} Textron Lycoming O-540-B2C5.<ref name="jawa08p2">Jackson 2008, p. 2</ref> ;Laviasa PA-25 Puelche 260 : Powered by {{convert|260|hp|kW|abbr=on}} O-540-G2A5 engine.<ref name="jawa08p2"/> ;Laviasa Puelche Trainer : Two seat trainer version of Puelche 235 with side-by-side seating.<ref name="jawa08p2"/>

==Accidents and incidents== *9 August 1974 a crop-spraying Pawnee was involved in [[1974 Norfolk mid-air collision|a fatal mid-air collision in Norfolk]], UK with a [[Royal Air Force]] [[McDonnell Douglas F-4]]M Phantom FGR.2.

==Specifications (PA-25-235 Pawnee B)== [[File:Piper PA-25 Pawnee C 3-view line drawing.png|frameless|right|3-view line drawing of the Piper PA-25 Pawnee C]]

{{Aircraft specs |ref=''Jane's All the World's Aircraft 1965–66'' <ref name="jawa65p290">Taylor 1965, p. 290</ref> |prime units?=imp  |genhide=

|crew=1 |capacity={{convert|150|USgal|impgal L|abbr=on}} or {{convert|1200|lb|kg|abbr=on}} 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={{convert|40|USgal|impgal L|abbr=on}}  |eng1 number=1 |eng1 name=[[Lycoming O-540|Lycoming O-540-B2B5]] |eng1 type=air-cooled six-cylinder [[horizontally-opposed engine]] |eng1 kw= |eng1 hp=235

|prop blade number=2 |prop name=McCauley 1A200/FA84 metal fixed-pitch propeller |prop dia m= |prop dia ft=7 |prop dia in=0

|perfhide=

|max speed kmh= |max speed mph=110 |max speed kts= |max speed note=at sea level |cruise speed kmh= |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):''' {{convert|1370|ft|m|abbr=on}} *'''Landing distance from 50 ft (15 m):''' {{convert|1350|ft|m|abbr=on}} |avionics= }}

==See also== '''Related development:''' *[[Texas A&M College Ag-1|Texas A&M College AG-1]] *[[Gippsland GA200|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|Embraer EMB-202 "Ipanema"]] *[[Grumman Ag Cat]] * [[PZL-106 Kruk]] * [[PZL-Mielec M-18 Dromader]] * [[Zlin Z-37 Čmelák]]

==Notes== {{Reflist}}

==Bibliography== *{{cite book |last=Bridgman|first=Leonard |author-link=Leonard Bridgman |title=Jane's All the World's Aircraft 1958–59 |year=1958 |location=London |publisher=Sampson Low, Marston & Company, Ltd. }} *{{cite journal |last1=Goodrum|first1=Alastair|title=Down Range: Losses over the Wash in the 1960s and 1970s|journal=Air Enthusiast |date=January–February 2004 |issue=109 |pages=12–17 |issn=0143-5450}} * Green, William. ''Aircraft Handbook''. London. Macdonald & Co. (Publishers) Ltd., 1964. * {{cite book |editor-last=Jackson |editor-first=Paul |title=Jane's All the World's Aircraft 208–2009 |year=2008 |location=Coulsdon, UK |publisher=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}} * [[John W. R. Taylor|Taylor, John W. R.]] ''Jane's All the World's Aircraft 1962–63''. London: Sampson Low, Marston & Company, Ltd., 1962. * {{cite book |last=Taylor |first=John W. R. |title=Jane's All the World's Aircraft 1965–66 |year=1965 |location=London |publisher=Sampson Low, Marston & Company, Ltd.}}

==External links== {{Commons category}} * [https://web.archive.org/web/20090720064811/http://www.dorotheen.de/fly/pa25.htm PA-25 Pawnee fliegerszene.de]

[[Category:Piper aircraft|Pawnee]] [[Category:Single-engined tractor aircraft]] [[Category:Low-wing aircraft]] [[Category:1950s United States agricultural aircraft]] [[Category:Glider tugs]] [[Category:Aircraft first flown in 1957]] [[Category:Aircraft with fixed conventional landing gear]] [[Category:Single-engined piston aircraft]]