Piper PA-42 Cheyenne

Template:Infobox Aircraft The Piper PA-42 Cheyenne is a turboprop aircraft built by Piper Aircraft. Aimed directly at Beech's successful King Air twin turboprop series, the PA-42 Cheyennes are larger developments of the earlier PA-31T Cheyennes I and II (in turn themselves turboprop developments of the PA-31 Navajo).

History

The Piper Cheyenne prototype first flew in 1969. Designated the (PA-31T-620), it was essentially a turboprop evolution of the Piper Navajo. Certification was granted May 3, 1972. The original Cheyenne, produced from 1974 to 1977, did not carry a roman numeral suffix designation. Powered by two Pratt and Whitney PTA-28 turboprops rated at 620-hp each. Because of difficulties complying with certification standards for longitudinal stability, the Cheyenne and later Cheyenne II are equipped with a Stability Augmentation System (SAS), consisting of an elevator-downsrping system (actuated by an angle-of-attack sensor) designed to provide the pilot with the appropriate stick force gradient - and to keep the airplane at its trim airspeed when flying near aft center of gravity loadings, high power settings, low airspeeds and high angles of attack. Without the SAS, the aircraft demonstrated neutral static stability in its flight regime. Later in 1978 it was re designated as the Cheyenne II (PA-31T-2-620), due to the production of the PA-31T-1-500.

In 1978 the Cheyenne I (PA-31T-1-500) was introduced. Powered by two 500-shp Pratt and Whitney PT6A-11 engines, the Cheyenne I was marketed as a low-cost step-up turboprop for Piper loyalists. Due to its reduced power, this airplane does not require a SAS. The Cheyenne IIXL (PA-31T-2-620XL) is a stretched (by two feet) version of the Cheyenne II. Certified February 1981 and built until 1984, it does not use SAS.

The Cheyenne IA (PA-31T-1A-500) certified May 1983 and produced until 1985, brought together several design improvements to the basic Cheyenne I. Redesigned cowling allow more air to flow into the engine; situating the propeller closer to the engine air scoop allows greater recovery of high-velocity ram air. New, streamlined exhaust stubs yield more jet thrust than previous models and kept nacelles soot accumulations to a minimum. Together, these changes allow higher inter turbine temperature (ITT) limits. Other improvements to the standard airplane airframe included an auto-ignition system, automatic starter disengage for simplified starting procedures and a larger windshield.

The PA-42-720 Cheyenne III was announced in September 1977. The first production Cheyenne III flew for the first time on May 18 1979 and FAA certification was granted in early 1980. Compared with the Cheyenne II the PA-42-720 was about 1m (3ft) longer, was powered by 537kW (720-shp) PT6A-41 turboshafts and introduced a T-tail, the most obvious external difference between the PA-31T and PA-42, as well as the most significant change to the series. Deliveries of production Cheyenne IIIs began on June 30 1980. The standard Cheyenne III has a full complement of deicing equipment, Q-tip propellers, more powerful 250-ampere/hour starter-generators and a 6.3-psi pressurization system backed up by an emergency system operated by the right engine's bleed air.

Also, several key upgrades found available for the Cheyenne IA became standard for the III. These included the SAS, redesigned exhaust stubs, which, according to piper, allowed an extra 6 kts IAS; and a redesigned engine intake air scoop, which allowed for a larger volume of air to enter the engine. In addition, an external air scoop for oil cooling was available instead of using engine intake air.

The IIIA superseded the Cheyenne III after 88 of the latter aircraft had been delivered. The IIIA is similar in appearance to the III but has more powerful PT6A-61 engines and 300 ampere/hour starter-generators. The IIIA also features an immproved air conditioning system. The IIIA's ordered by Lufthansa feature flight decks configured to resemble that airline's Airbus A310. Alitalia also uses the IIIA for training purposes.

The higher powered and significantly faster PA-42-1000 is basically a PA-42-720 with far more powerful 745kW (1000hp) Garrett TPE331 turboprops driving four blade, 106-inch diameter, composite-construction Dowty Rotol propellers. The Cheyenne 400LS originally designated the IV, is the hot-rod of the line. In production from 1984 to 1993, it was designated to compete with the performance of smaller fanjets.

Criticism

The adverse publicity generated by the litigation following two similar Cheyenne II takeoff accidents did much to tarnish the airplane's and Piper's image. The worst of the courtroom allegations, that the Cheyenne II demonstrates unstable longitudinal stability and overly sensitive pitch characteristics, was heavily publicized in 1983 and 1984 after inquiries into the circumstances surrounding the certification of these airplanes.

However, the Cheyenne IIIA's accident rate has been exemplary (as of 1990). From 1983 to 1985, the aircraft generated only three airworthiness directives. In 1986 and 1987 there were no airworthiness directives.

Variants

Piper PA-42-720 Cheyenne III

• Cheyenne III, model PA-42-720, equipped with Pratt & Whitney Canada PT6A-41 engines
• Cheyenne IIIA, model PA-42-720, equipped with PT6A-61 engines
• Cheyenne IV, model PA-42-1000, later the Cheyenne 400LS, and then Cheyenne 400. This is the largest aircraft ever made by Piper, with only 45 built. Powered by 1000 SHP Garrett TPE-331 engines, and 4 bladed props.

Specifications (PA-42-720)

General characteristics

• Crew: One or two
• Capacity: 6 to 9 passengers

Performance

References

http://www.airliners.net/info/stats.main?id=314

AOPA Pilot, June 1987. Page 38 & 39