The Piper Cheyenne I (PA–31T-1-500) and Cheyenne IA (PA–31T-1A-500) are successor versions to the twin-turboprop Cheyenne II. The Cheyenne I/IA designation can be confusing, because the first Cheyenne models to be brought to market were renamed Cheyenne IIs after the I and IA were rolled out. So the II came out first, in 1974, but the I/IAs came out later, and were produced from 1978 to 1984. The main difference between the II and I/IA is engine power. The 277-knot Cheyenne IIs come with 620-shp Pratt & Whitney PT6A-28 engines; the I and IA have 500-shp Pratt & Whitney PT6A-11 engines and so have lower max cruise speeds. The II’s extra power proved to have a destabilizing tendency in high-power, low-airspeed regimes, so the II and IIXL were fitted with a stability augmentation system to eliminate any potentially dangerous pitch responses. The Cheyenne I/IAs don’t require stability augmentation.
The Cheyenne IA, which earned FAA approval in May 1983, offered redesigned engine cowlings and exhaust stubs, yielding 4 percent more horsepower at high altitudes, and improved cruise speed to 261 knots. Standard fuel capacity is 308 gallons; optional tip tanks bring it to 390 gallons.
Aftermarket enhancements for the Cheyenne I series include engine conversions from Blackhawk Modifications of Waco, Texas. The XP28 package replaced the twin turboprop’s original 500-shp PT6A-11 engines with 620-shp PT6A-28 powerplants flat-rated to 500 shp. Performance improvements include greater climb rates; less time, distance, and fuel to climb; and 25-knot-faster cruise speeds. Including four-blade Hartzell or McCauley propellers is an option. Blackhawk also can install 750-shp PT6A-135A powerplants, which enables retrofitted Cheyenne Is to achieve max cruise speeds of 280 knots while reducing time to climb and extending range.
A total of 215 Cheyenne I and IAs were built, and 143 remain on the FAA registry. Current Vref prices for the aircraft range from $340,000 for a 1978 Cheyenne I to $470,000 for a 1984 Cheyenne IA. Some aircraft that have been updated with Avidyne or Garmin avionics have higher asking prices.
Robert C. Searles is a writer and editor specializing in commercial, military, and general aviation.
SPEC SHEET
Cheyenne I Specifications
- Engines: Two Pratt & Whitney PT6A-11s, flat-rated to 500 shp
- Seats: Up to 8 (including two pilots)
- Max takeoff weight: 8,700 pounds
- Max cruise speed: 249 knots
- Takeoff distance: 1,429 feet
- Max range: 1,330 nm
- Wingspan: 40 feet, 8 inches
- Length: 34 feet, 8 inches
- Height: 12 feet, 9 inches
Cheyenne IA Specifications
- Engines: Two Pratt & Whitney PT6A-11s, flat-rated to 500 shp
- Seats: Up to 8 (including two pilots)
- Max takeoff weight: 8,700 pounds
- Max cruise speed: 261 knots
- Takeoff distance: 1,429 feet
- Max range: 1,285 nm
- Wingspan: 40 feet, 8 inches
- Length: 34 feet, 8 inches
- Height: 12 feet, 9 inches
