Piper PA-42 Cheyenne

PA-42 Cheyenne
Cheyenne 400LS
Role	Turboprop
Manufacturer	Piper Aircraft
First flight	May 18, 1979
Produced	1979-1993
Number built	192; 149 IIIAs and 43 400s
Unit cost	$429,000 base in 1975 $1,830,000 in 2012 USD
Developed from	Piper PA-31T Cheyenne

The Piper PA-42 Cheyenne is a turboprop aircraft built by Piper Aircraft. The PA-42 Cheyenne is a larger development of the earlier PA-31T Cheyennes I and II (which are, in turn, turboprop developments of the PA-31 Navajo).

The Piper Cheyenne prototype first flew in 1969. Designated the PA-31T-620, it was essentially a turboprop evolution of the Piper PA-31 Navajo, powered by two Pratt & Whitney Canada PT6A-28 turboprops rated at 620 hp (460 kW) each. Certification was granted on 3 May 1972. The original Cheyenne, produced from 1974 to 1977, did not carry a Roman numeral suffix designation. 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 a stick-pusher 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 redesignated 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 (370 kW) 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 an SAS. The Cheyenne IIXL (PA-31T-2-620XL) is a stretched (by two feet) version of the Cheyenne II. Certified in 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. A redesigned cowling allowed more air to flow into the engine; situating the propeller closer to the engine air scoop allowed greater recovery of high-velocity ram-air. New, streamlined exhaust stubs yielded more jet thrust than previous models and kept nacelle soot accumulation to a minimum. Together, these changes allowed 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.