page_title: Piper PA-31 Navajo
section_title: Design and development
hierarchical_section_title: Piper PA-31 Navajo / Design and development
caption_attribution_description: English: An early-build Piper PA-31 Navajo VH-XGL (c/no. 31-30) parked at Melbourne's Essendon Airport in Australia.
context_page_description: 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.
context_section_description: 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 (231 kW) 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 6,200 lb (2,812 kg) to 6,500 lb (2,948 kg).
  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 (224 kW) 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 (317 kW) Lycoming TIGO-541-E engines and compared to earlier models had a longer nose, fewer and smaller windows, 25 US gal (95 l) 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 (3,538 kg). 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 2 ft 0 in (0.61 m), allowing for up to ten seats in total. Variants of the Lycoming TIO-540 developing 350 hp (261 kW) were fitted to the Chieftain, with an opposite-rotation LTIO-540 installed on the right-hand wing; MTOW was increased to 7,000 lb (3,175 kg). 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 (242 kW). 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 (151 L) auxiliary fuel tanks in each wing of t
caption: The 30th production Navajo, fitted with two-bladed propellers and early two-part airstair cabin entry door (without the third door, introduced later)
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