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 310 hp 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 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 from 6,200 lb to 6,500 lb.
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 300 hp 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 425 hp Lycoming
TIGO-541-E engines and compared to earlier models had a longer nose, fewer and smaller
windows, 25 US gal 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 7,800 lb. 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 airconditioning, 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 2 ft
0 in, allowing for up to ten seats in total. Variants of the Lycoming TIO-540 developing
350 hp were fitted to the Chieftain, with an opposite-rotation LTIO-540 installed on
the right-hand wing; MTOW was increased to 7,000 lb. 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 325 hp. 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 40 US gal
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 700 lb 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 11 ft 6 in 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 4 ft increase in wingspan and greater fuel capacity of 243 US gal. 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 7,200 lb was 200 lb 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 less than 100 aircraft. Two experimental PA-31-353s were also built in the mid-1980s.
Licenced 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 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
PA-31 Navajo 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
310 hp Lycoming TIO-540-E turbo-charged piston engines, new airconditioning and optional
pilot access door and optional wide utility door.
PA-31 Navajo C Marketing name for 1974 improved variant with
310 hp 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 Lycoming TIGO-541-E1A piston engines.
PA-31-325 Navajo Referred to as the "Navajo C/R" for Counter-rotating;
variant of Navajo with counter-rotating engines introduced with the PA-31-350 Chieftain. 325 hp
Lycoming TIO-540 / LTIO-540 engines PA-31-350 Chieftain
Stretched version of the Navajo with more powerful 350-hp counter-rotating engines 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. First flight September 25, 1981. 21 built.
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.
PA-31-353 Experimental version of PA-31-350; two built.
T1050 Unbuilt airliner variant with fuselage lengthened
by 11 ft 6 in compared to the PA-31-350. EMB 820C
Version of Chieftain built under licence 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
8,003lbs was 1000lbs more than that of the Chieftain.
Colemill Panther Re-engined Navajo with 350 hp Lycoming TIO-540-J2B
engines, four-blade "Q-Tip" propellers and optional winglets. Conversion designed by
Colemill Enterprises of Nashville, Tennessee. 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
Bahamas Royal Bahamas Defence Force
Finland Finnish Air Force Former operator
France French Navy Former operator
Honduras Honduras Air Force
Kenya Kenya Air Force Former operator
Dominican Republic Dominican Air Force
Sweden Royal Swedish Air Force
Royal Swedish Navy Trinidad and Tobago
Trinidad and Tobago Defence Force Former Operator Specifications
Data from Jane's All The World's Aircraft 1976–77
General characteristics Crew: one or two
Capacity: five to seven passengers Length: 32 ft 7½ in
Wingspan: 40 ft 8 in Height: 13 ft 0 in
Wing area: 229 sq. ft Empty weight: 3,930 lb
Max. takeoff weight: 6,500 lb Powerplant: 2 × Lycoming TIO-540-A air-cooled
six-cylinder horizontally opposed piston engine, 310 hp each
Propellers: Two or three blade, metal, fully feathering, Hartzell propeller
Performance Never exceed speed: 236 knots)
Maximum speed: 227 knots) at 15,000 ft Cruise speed: 207 knots) econ cruise at 20,000 ft
Stall speed: 63.5 knots) flaps down Range: 1,011 nmi)
Service ceiling: 26,300 ft Rate of climb: 1,445 ft/min
See also
Related development Piper PA-31T Cheyenne
Aircraft of comparable role, configuration and era
Beechcraft Queen Air Cessna 402
Cessna 414 Aero Commander 500
References Notes
Bibliography Barnett, Cliff. "Piper looks ahead" Flight
International magazine, 24 September 1983, p.833 retrieved 2010-04-03.
Bonelli, Regis and Pinheiro, Armando Castelar. New Export Activities in Brazil: Comparative
Advantage, Policy or Self-Discovery, 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.
Lambert, Mark. "In the air: Piper PA-30 Twin Comanche", Flight International magazine,
12 September 1963, pp. 468–470. Levy, Howard. "Piper consolidates at Lakeland",
Flight International magazine, 30 April 1983, pp.1152 and 1153. Online archive version retrieved
2010-04-03. Marsh, David. EUROCONTROL Trends in Air Traffic,
volume 1; Getting to the Point: Business Aviation in Europe European Organisation for the Safety
of Air Navigation May 2006. Retrieved 2010-04-11. Michell, Simon. Jane's Civil and Military
Aircraft Upgrades 1994–95. Coulsdon, UK: Jane's Information Group, 1994. ISBN 0-7106-1208-7.
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 Taylor, John W.R. Jane's All The World's Aircraft
1976–77. London: Jane's Yearbooks, 1976, ISBN 0-354-00538-3.
Taylor, John W.R. Jane's All The World's Aircraft 1982–83. London: Jane's Yearbooks, 1982,
ISBN 0-7106-0748-2.