Piper PA-31 Navajo

The Piper PA-31 Navajo is a family of cabin-class, twin-engined aircraft designed and built by Piper Aircraft for the general aviation market, most using Lycoming engines. It was also license-built in a number of Latin American countries. Targeted at small-scale cargo and feeder liner operations and the corporate market, the aircraft was a success. It continues to prove a popular choice, but due to greatly decreased demand across the general aviation sector in the 1980s, production of the PA-31 ceased in 1984.

Design and development

At the request of company founder William T. Piper, Piper began development of a six- to eight-seat twin-engined corporate and commuter transport aircraft in 1962 under the project name ''Inca''. The type, now designated the PA-31 and looking like a scaled-up Twin Comanche, was officially announced in late 1964 after its first flight on 30 September that year. It was a low-wing monoplane with a conventional tail, powered by two Lycoming TIO-540-A turbocharged engines in so-called "tiger shark" cowlings, a feature shared with the Twin Comanche and also the PA-23 Aztec. As testing proceeded two cabin windows were added to each side of the fuselage and the engines moved further forward. The PA-31, now named "Navajo" after a Native American tribe, was not certified by the Federal Aviation Administration (FAA) until 24 February 1966, and deliveries did not begin until the following year, after the type was recertified in mid-1966 with an increase in maximum takeoff weight (MTOW) from to .

The PA-31-300 was the next model, certified by the FAA in June 1967. This model was the only one of the PA-31 series not to have turbocharged engines. A pair of Lycoming IO-540-M1A5 engines were fitted to the PA-31-300, driving two-bladed propellers. Following the introduction of the PA-31-300 the turbocharged model began to be known unofficially as the PA-31-310. The PA-31-300 was only produced in 1968 and 1969 and had the smallest production total for any PA-31 series model, with only 14 aircraft built.

The next member of the family was also Piper's first pressurized aircraft, the PA-31P Pressurized Navajo, certified in late 1969. Development of the PA-31P had begun in January 1966, before the FAA had awarded the PA-31 a type certificate. The PA-31P was powered by Lycoming TIGO-541-E engines and compared to earlier models had a longer nose, fewer and smaller windows, fuel tanks in the engine nacelles and a one-piece airstair cabin entry door instead of the split pair of doors on the unpressurized models. MTOW was greatly increased at . Also known unofficially as the PA-31P-425, the PA-31P was produced from 1970 to 1977.

In 1971, Piper introduced improvements to the PA-31 model. The Navajo B featured air conditioning, increased baggage space achieved by the addition of storage lockers in the rear part of extended nacelles, a third door next to the cabin entry doors to facilitate the loading of baggage, and an optional separate door for the pilot to enter the cockpit.

In September 1972, Piper unveiled the PA-31-350 Navajo Chieftain, a stretched version of the Navajo B with more powerful engines and counter-rotating propellers to prevent critical engine handling problems. The fuselage was lengthened by , allowing for up to ten seats in total. Variants of the Lycoming TIO-540 developing were fitted to the Chieftain, with an opposite-rotation LTIO-540 installed on the right-hand wing; MTOW was increased to . The Chieftain's introduction was delayed by a flood at Piper's factory at Lock Haven, Pennsylvania, caused by Hurricane Agnes, and deliveries did not commence until 1973. In 1974, Piper used a Navajo B as the basis for developing a new model, the PA-31-325 Navajo C/R. The Navajo C/R had lower-power versions of the counter-rotating engines of the Chieftain, rated at . After certification of the PA-31-325 in May 1974, production commenced in the 1975 model year. The Navajo B was also superseded in the 1975 model year, by the Navajo C version of the PA-31 model.

Piper established its T1000 Airliner Division in May 1981 at its Lakeland, Florida factory. There were two aircraft in the T1000 series. The T1020, or more accurately the PA-31-350T1020 was a PA-31-350 Chieftain optimized for and marketed for the commuter airline market. It featured reduced fuel capacity compared to the standard Chieftain, with the auxiliary fuel tanks in each wing of the Chieftain not fitted to the T1020. It also had reduced baggage capacity ( maximum instead of the Chieftain's maximum) and up to eleven seats. The first T1020 was delivered in December 1981. The second aircraft in the T1000 stable was the T1040 – the PA-31T3 model. The T1040 was a hybrid, featuring the main fuselage of the PA-31-350T1020 with the nose and tail of the PA-31T1 Cheyenne I. The wings were similar to the Cheyenne I's, but with reduced fuel capacity and baggage lockers in the engine nacelles similar to those of the Chieftain. An optional underbelly cargo pod was also available. The Pratt & Whitney Canada PT6A-11 turboprop engines were the same as those of the Cheyenne I. Deliveries of the T1040 began in July 1982. A T1050 variant with a fuselage stretch of and seating capacity for 17 was proposed as a factory conversion of existing aircraft, but did not proceed.

The last member of the PA-31 family to enter production was the PA-31P-350 Mojave. Like the T1040 the Mojave was a hybrid, but whereas the T1040 was essentially a turboprop Chieftain the Mojave was more or less a piston-engined version of the Cheyenne. The Mojave combined the fuselage of the Cheyenne I with the tail of the Chieftain. The wings were similar to the Chieftain's, but with greater structural strength, a increase in wingspan and greater fuel capacity of . The engines were slightly different variants of the Chieftain's TIO-540 and LTIO-540, being fitted with intercoolers, and like the Chieftain, had baggage lockers on the rear part of the nacelles. The Mojave's MTOW of was higher than the Chieftain's. Certified in 1983, like the T1020 and T1040 the Mojave was introduced at a time of economic recession and was produced only in 1983 and 1984; combined production of the T1020, T1040 and Mojave amounted to fewer than 100 aircraft. Two experimental PA-31-353s were also built in the mid-1980s.

Licensed manufacture

The PA-31 series was manufactured under licence in several countries from kits of parts supplied by Piper. Chincul SACAIFI in Argentina assembled most of the series as the PA-A-31, PA-A-31-325, PA-A-31P and PA-A-31-350 and Aero Industrial Colombiana SA (AICSA) in Colombia assembled PA-31, PA-31-325 and PA-31-350 aircraft. The PA-31-350 Chieftain was also assembled under licence in Brazil by Embraer as the EMB 820C Navajo. In 1984, Embraer subsidiary company Indústria Aeronáutica Neiva began converting Embraer EMB 820Cs by installing Pratt & Whitney Canada PT6 turboprop engines; Neiva called the converted aircraft the Carajá.

Variants

;
:Initial production version, also known unofficially as the PA-31-310.

;PA-31-300 Navajo
:Variant of the Navajo with normally aspirated engines; 14 built.

;PA-31 Navajo B
:Marketing name for 1971 improved variant with Lycoming TIO-540-E turbo-charged piston engines, new airconditioning and optional pilot access door and optional wide utility door.Peperell 1987, pp. 179-201

;PA-31 Navajo C
:Marketing name for 1974 improved variant with Lycoming TIO-540-A2C engines and other minor improvements.

;PA-31P Pressurized Navajo
:Pressurized version of the PA-31 Navajo, powered by two 425-hp (317-kW) Lycoming TIGO-541-E1A piston engines.

;
:Referred to as the "Navajo C/R" for Counter-rotating; variant of Navajo with counter-rotating engines introduced with the PA-31-350 Chieftain. Lycoming TIO-540 / LTIO-540 engines

;
:Stretched version of the Navajo with more powerful 350-hp (261-kW) counter-rotating engines (a Lycoming TIO-540 and a Lycoming LTIO-540) to eliminate critical engine issues.

;PA-31P-350 Mojave
:Piston-engined variant of the PA-31T1 Cheyenne I; 50 aircraft built.

;PA-31-350T1020
:Also known as the T1020/T-1020; variant of the PA-31-350 Chieftain optimised for commuter airline use, with less baggage and fuel capacity and increased seating capacity (nine passengers). First flight September 25, 1981. 21 built.Taylor 1982, pp. 450–451.

;PA-31T3
:Also known as the T1040/T-1040; turboprop-powered airliner with fuselage of the PA-31-350T1020, and wings, tail and Pratt & Whitney Canada PT6A-11 engines of PA-31T Cheyenne. First flight July 17, 1981. 24 built.Taylor 1982, p. 451.

;PA-31-353
:Experimental version of PA-31-350; two built.

;T1050
:Unbuilt airliner variant with fuselage lengthened by compared to the PA-31-350.

;EMB 820C
:Version of Chieftain built under license by Embraer in Brazil.

;Neiva Carajá
:Turboprop conversion of EMB 820C, fitted with two Pratt & Whitney Canada PT6A-27 engines flat-rated to 550shp. The Carajá's MTOW of was more than that of the Chieftain.

;Colemill Panther
:Re-engined Navajo with Lycoming TIO-540-J2B engines, four-blade Hartzell "Q-Tip" propellers and optional winglets. Conversion designed by Colemill Enterprises of Nashville, Tennessee.Michell 1994, p. 305. The supplemental type certificates (STCs) were subsequently sold to Mike Jones Aircraft Sales, which continues to convert PA-31, PA-31-325 and PA-31-350 variants with Colemill-developed features.

Operators

Civil

The Navajo family is popular with air charter companies and small feeder airlines in many countries, and is also operated by private individuals and companies.

Military

;Chile
* Chilean Navy purchased a single PA-31 in 1971.
;Colombia
* Colombian Air Force
* Colombian Navy
; Dominican Republic
* Dominican Republic Air Force operates two PA-31s as of December 2018.Hoyle ''Flight International'' 4–10 December 2018, p. 43.
;Finland
* Finnish Air Force operated the PA-31-350 Chieftain in the liaison and light transport role.
;France
* French Navy former operator
;Honduras
* Honduran Air Force operates one PA-31 as of December 2018.
;Kenya
* Kenya Air Force operated a Navajo Chieftain in the VIP role.
;Spain
* Spanish Air Force
;United Kingdom
* Aeroplane and Armament Experimental Establishment former operator

Accidents and incidents

* December 3, 1983: SouthCentral Air Flight 59, a PA-31-350 registered ''N35206'', carrying eight passengers and one pilot, was on the takeoff roll at Anchorage International Airport when it collided head-on with Korean Air Lines Flight 084, a McDonnell Douglas DC-10-30 freighter ''HL7339''. The Piper struck the DC-10's left and center main landing gear and three passengers sustained minor injuries; the DC-10 overran the runway and the three crew suffered serious injuries. Investigators determined that the Korean Air Lines pilot had become disoriented taxiing in fog, failed to follow correct procedures and confirm his position, and accidentally initiated takeoff from the wrong runway. Both aircraft were severely damaged and were written off.

Aircraft on display

;Spain
* A PA-31P Pressurized Navajo formerly operated by the Spanish Air Force is on display at the Museo del Aire in Madrid.“Piper Navajo”, information placard, Museo del Aire

Specifications (PA-31 Navajo)

See also

References

Citations

Bibliography

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"Piper looks ahead".
''Flight International'', 24 September 1983, Vol. 124, No. 3881. p.833.
* Bonelli, Regis and Pinheiro, Armando Castelar
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Research Network Working Paper #R-551, Inter-American Development Bank, July 2008.
*''Flight Magazine'', Volume 54, No. 11, November 1965. Air Review Publishing Corporation, Dallas, Texas.
* Hoyle, Craig. "World Air Forces Directory". ''Flight International'', 4–10 December 2018, Vol. 194, No. 5665, pp. 32–60.
* Lambert, Mark
"In the air: Piper PA-30 Twin Comanche.
''Flight International'', 12 September 1963, Vol. 84, No. 2844, pp. 468–470.
* Levy, Howard
"Piper consolidates at Lakeland".
''Flight International'', 30 April 1983, Vol. 123, No. 3860, pp. 1152–1153.
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''EUROCONTROL Trends in Air Traffic'' Volume 1: ''Getting to the Point: Business Aviation in Europe''
European Organisation for the Safety of Air Navigation (EUROCONTROL) May 2006. Retrieved 2010-04-11.
* Michell, Simon. ''Jane's Civil and Military Aircraft Upgrades 1994–95''. Coulsdon, UK: Jane's Information Group, 1994. .

Piper Aircraft Inc. ''Customer Service Information File'' 2009
retrieved 2010-04-08
*''Piper Airplane Parts Catalog: PA-31 Navajo, PA-31-300 Navajo, PA-31-325 Navajo C/R; September 10, 2009.'' Piper Aircraft Corporation, Manual Part Number 753-703
*''Piper Navajo Information Manual, Revision 9, March 18, 1994.'' Piper Aircraft Corporation, Manual Part Number 761-723
*''Piper Navajo Pilot's Operating Manual, Revision 34, April 22nd 2002.'' Piper Aircraft Corporation, Manual Part Number 761-456
*''Piper T1020 Parts Catalog, Revision 10, September 10, 2009.'' Piper Aircraft Corporation, Manual Part Number 761-775
* Sixma, Herman J. and Jyrki Laukkanen. "Far Northern Air Force: The Finnish Air Arm Today". '' Air International'', July 1986, Vol. 31, No. 1. pp. 7–13. .
* Taylor, John W. R. ''Jane's All The World's Aircraft 1976–77''. London: Jane's Yearbooks, 1976, .
* Taylor, John W. R. ''Jane's All The World's Aircraft 1982–83''. London: Jane's Yearbooks, 1982, .
* Wheeler, Barry C
"World's Air Forces 1979"
''Flight International'', 4 August 1979, Vol. 116, No. 3672. pp. 333–386.

{{Swedish military aircraft designations

1960s United States civil utility aircraft
Aircraft first flown in 1964
Low-wing aircraft
Navajo
Twin piston-engined tractor aircraft