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Piper PA-31T Cheyenne / T-1020 / T-1040
Schafer Comanchero 750


pipercheyanne
Cheyenne I


A version known as the T-1020 was expected to continue the commuter line but was little more than a revamped Chieftain. The T-1020 is a Chieftain with many small changes designed to make the most of the airplane for commuter use. Not pressurized, it can carry nine to 11 passengers.

A significant advance in the Navajo family came on 22 October 1973 when Piper flew the first production example of the PA-31T Cheyenne, which combined an airframe generally similar to that of the Pressurized Navajo with two 462kW Pratt & Whitney Aircraft of Canada PT6A-28 turboprop engines. The Piper Cheyenne was certificated in 1974, just as the new surge in turboprops started, the Cheyenne is a product of proven airframe and powerplant technology that dates back to the mid 1960s.

A piston-engined version of the turbine Cheyenne I known as the Mojave was introduced but production ceased that same year after only 50 had been completed.

The first of these models to be marketed was the Cheyenne in 1974 (renamed the Cheyenne II in 1978) when a simplified version known as the Cheyenne I was introduced.

Production of the PA-31P Pressurized Navajo ended during 1977, at which time a total of 248 had been built, but at the same time the company introduced a new version of the Cheyenne, the PA-31T-1 Cheyenne I, the original Cheyenne then becoming redesignated PA-31T Cheyenne II. Deliveries of the new Cheyenne I, which differed primarily from its predecessor by having 373kW Pratt & Whitney Aircraft of Canada PT6A-11 turboprop engines, began towards the end of April 1978.

When Piper mated the 680-hp Pratt & Whitney PT6A-28 with the airframe of their pressurized Navajo, they produced a turboprop that had an instant heritage. The PT6A-28, which is derated to 620-hp in the Cheyenne II so that takeoff power can be maintained up to 4,800 feet, also powers three models of the King Air. Because of its long and reputable service record, the PT6A-28 is authorized to operate 3,500 hours between overhauls in the Cheyenne. That figure was stipulated principally because Pratt & Whitney felt that the 6,500-hour TBO authorized for commuter aircraft, such as the Beech 99 and the Twin Otter, would allow too long a calendar time between internal inspections, considering that typical business aircraft in the Chey-enne class fly about 600 hours per year.

Since the Cheyenne uses the fuselage design of the pressurized Navajo, the reliability of the pressure vessel and its environmental units (35,000 BTU heater, 23,000 BTU vapor-cycle air conditioning system and dehumidifier) has been established, and that should mean reduced maintenance worries for the Cheyenne owner. Furthermore, pressurizing a turboprop is less complicated than is pressurizing a turbosupercharged aircraft, because high-pressure bleed air from the engine's compressor can be mixed with the cool outside air to produce the desired pressure differential, which for the Cheyenne is 5.5 psi.

The thirsty turbine powerplants of the Cheyenne necessitated a redesign of the fuel system, and the result was more than just an increased capacity. The Cheyenne's 382 USG of usable fuel are contained in two multi-celled wing tanks one per side. Although each fuel tank consists of four separate but interconnected tanks, the pilot's fuel-control options are reduced to a simple on/ off/cross-feed arrangement. The three fuel cells located within each wing are filled through an opening in each engine nacelle; they must be serviced before the tip tank, which constitutes the fourth fuel cell for each wing. Gravity causes fuel from the 22-USG tip tank to flow into the wing fuel cells. Therefore, opening a nacelle filler cap when the tip tanks are full will result in some spilling, usually on the offending preflighter. However, checking that the tip tanks are full assures that all the cells are topped, and fuel in the neck of the nacelle filler indicates that the corresponding three wing cells are full to their combined capacity of 173 USG.

Installing 1,240 total horsepower in the Pressurized Navajo's airframe, which was originally designed to accept 850 hp, necessitated either a larger horizontal stabilizer or an innovative redesign of the flight control system if the required stability criteria were to be met. Piper chose the latter course and installed a relatively simple stability augmentation system that varies the tension in the Cheyenne's elevator downspring as a function of the aircraft's angle of attack. Although the Cheyenne's SAS initially caused some consternation among Piper's salespeople, who were forced to explain why their machine required an operative stability augmentation system to be airworthy while the competition's aircraft didn't, the Cheyenne's SAS has proved to be a successful and cost-effective way of engineering a solution to the classic problem of maintaining stability while increasing the horsepower of an existing design. Price 1976: $623,805.

The T-1040 is a turbine powered hybrid combining the fuselage of the Navajo Chieftain with the wing, tail and engines of the Cheyenne 1 A to create a new commuter airliner. Not pressurized, it can carry nine to 11 passengers.

The Cheyenne range was extended for 1981 by introduction of the PA-31T-2 Cheyenne IIXL, with the fuselage lengthened by 0.61m and 559kW Pratt & Whitney Aircraft of Canada PT6A-135 engines flat-rated to 462kW.

Schafer Aircraft Modifications Inc was founded 1977, and from 1979 developed modifications for other aircraft. Included was installing higher rated turboprops to Piper Cheyenne II as the Schafer Comanchero 750.

Certification:
FAA A8EA
PA-31T & PA-31T3
31T-740002 to
31T-7620057
31T-7720001 to
31T-7920094
31T-8275001 and up

Specifications:

PA-31T-500T1 Cheyenne I
First built: 1978
Engines: 2 x P&W PT6A-11, 500 shp
Props: Hartzell 3-blade, 93-in
Seats: 7
Length: 34.7 ft
Height: 12.8 ft
Wingspan: 40.7 ft
Wing area: 229 sq.ft
Wing aspect ratio: 7.2
Maximum ramp weight: 8750 lb
Maximum takeoff weight: 8700 lb
Standard empty weight: 4904 lb
Maximum useful load: 3843 lb
Zero-fuel weight: 7200 lb
Maximum landing weight: 8700 lb
Wing loading: 38 lbs/sq.ft
Power loading: 8.7 lbs/hp
Maximum usable fuel: 2559 lb
Best rate of climb: 1750 fpm
Service ceiling: 28,200 ft
Max pressurisation differential: 5.5 psi
8000 ft cabin alt @: 25,000 ft
Maximum single-engine rate of climb: 413 fpm @ 110 kt
Single-engine climb gradient: 225 ft/nm
Single-engine ceiling: 12,500 ft
Maximum speed: 243 kt
Normal cruise @ 24,000ft: 234 kt
Fuel flow @ normal cruise: 412 pph.
Endurance at normal cruise: 5.5 hr
Stalling speed clean: 84 kt
Stalling speed gear/flaps down: 72 kt
Turbulent-air penetration speed: 180 kt

PA-31T-620 Cheyenne II
First built: 1974
Engines: 2 x P&W PT6A-28, 620 shp
TBO: 3,500 hr
Props: Hartzell 3-blade, constant-speed reversing and full-feathering, 93-in
Seats: 8
Length: 34 ft. 8 in
Height: 12 ft. 9 in
Wingspan: 42 ft. 8 in / 13.01 m
Wing area: 229 sq.ft / 21.3 sq.m
Airfoil: NACA 632-415 at root, 63A212 at tip
Aspect ratio: 7.96
Maximum ramp weight: 9050 lb
Maximum takeoff weight: 9000 lb
Empty weight: 5,331 lb
Useful load: 3,719 lb
Payload with full fuel: 1,427 lb
Ramp weight: 9,050 lb
Zero-fuel weight: 7200 lb
Maximum landing weight: 9000 lb
Wing loading: 39.3 lbs/sq.ft
Power loading: 7.26 lb/hp
Usable fuel capacity: 382 USG/2,292 lb
Baggage capacity: 400 lb
Baggage area: 42 cu.ft
Best rate of climb: 2710 fpm
Certificated ceiling: 31,600 ft
Service ceiling: 29,000 ft
Single-engine service ceiling: 14,600 ft
Max pressurisation differential: 5.5 psi
8000 ft cabin alt @: 25,000 ft
Maximum single-engine rate of climb: 660 fpm @ 113 kt
Single-engine climb gradient: 350 ft/nm
Maximum speed: 283 kt
Maximum cruise (@ 11,000 ft.): 279 kt
Economy cruise (@ 25,000 ft.): 212 kt
Range @ maximum cruise (45-min res). 883 nm
Range @ economy cruise (45-min res): 1,350 nm
Normal cruise @ 24,000ft: 248 kt
Fuel flow @ normal cruise: 454 pph
Endurance at normal cruise: 5.1 hr
Stall speed (clean): 89 kt
Stall speed (gear, flaps down): 77 kt
Turbulent-air penetration speed: 180 kt
Minimum runway requirement: 2,480 ft.

PA-31T-2XL620 Cheyenne IIXL
First built: 1981
Engines: 2 x P&W PT6A-135, 620 shp
Props: Hartzell 3-blade, 93-in
Seats: 6/8
Length: 36.7 ft
Height: 12.8 ft
Wingspan: 42.7 ft
Wing area: 222 sq.ft
Wing aspect ratio: 8
Maximum ramp weight: 9540 lb
Maximum takeoff weight: 9474 lb
Standard empty weight: 5112 lb
Maximum useful load: 4428 lb
Zero-fuel weight: 7600 lb
Maximum landing weight: 9000 lb
Wing loading: 41.4 lbs/sq.ft
Power loading: 7.6 lbs/hp
Maximum usable fuel: 2292 lb
Best rate of climb: 1750 fpm
Service ceiling: 30,000 ft
Max pressurisation differential: 5.5 psi
8000 ft cabin alt @: 25,000 ft
Maximum single-engine rate of climb: 470 fpm @ 122 kt
Single-engine climb gradient: 231 ft/nm
Single-engine ceiling: 14,900 ft
Maximum speed: 276 kt
Vmca: 91 kt
Normal cruise @ 29,000ft: 246 kt
Fuel flow @ normal cruise: 394 pph
Endurance at normal cruise: 5.3 hr
Stalling speed clean: 89 kt
Stalling speed gear/flaps down: 80 kt
Turbulent-air penetration speed: 187 kt

PA31 T-1020 Commuter
First built: 1981
Engine: 2 x Lycoming TIO-540, 350 hp
TBO: 1800 hr
Prop: Hartzell 3 blade, constant speed 80 in
Seats: 11
Length: 34.6 ft.
Height: 13 ft
Wingspan: 40.7 ft
Wing area: 229 sq.ft
Wing aspect ratio: 7.2
Max ramp wt: 7045 lb
Max take off wt: 7000 lb
Standard empty wt: 4450 lb
Max useful load: 2550 lb
Max landing wt: 7000 lb
Wing loading: 30.6 lbs/sq.ft
Power loading: 10 lbs/hp
Max useable fuel: 636 lb
Climb rate: 1120 fpm @ 101 kt
Climb gradient: 665 ft/nm
Rate of climb @ 8000 ft: 950 fpm
Certificated ceiling; 24,000 ft
SE rate of climb: 230 fpm @ 106 kt
SE climb gradient: 128 ft/nm
SE ceiling: 13,700 ft
Max speed: 231 kt
Cruise @ 65% power @ 8,000ft: 181 kt
Fuel flow @ 65% power @ 8,000ft: 185 pph
Endurance @ 65% power @ 8,000ft: 3.2 hr
Stalling speed clean: 77 kt
Stall speed gear/flaps down: 74 kt
Turbulent air penetration speed: 160 kt
Retractable undercarriage

PA-31 T-1040
First built: 1982
Engines: 2 x P&W PT6A-11, 500 shp
Props: Hartzell 3-blade, 93-in
Seats: 11
Length: 36.7 ft
Height: 12.8 ft
Wingspan: 41.1 ft
Wing area: 229 sq.ft
Wing aspect ratio: 7.4
Maximum ramp weight: 9050 lb
Maximum takeoff weight: 9000 lb
Standard empty weight: 4624 lb
Maximum useful load: 2976 lb
Zero-fuel weight: 7600 lb
Maximum landing weight: 9000 lb
Wing loading: 39.3 lbs/sq.ft
Power loading: 9 lbs/hp
Maximum usable fuel: 2010 lb
Best rate of climb: 1610 fpm
Service ceiling: 27,900 ft
Maximum single-engine rate of climb: 325 fpm @ 115 kt
Single-engine climb gradient: 169 ft/nm
Single-engine ceiling: 12,100 ft
Maximum speed: 243 kt
Normal cruise @ 11,000ft: 236 kt
Fuel flow @ normal cruise: 580 pph
Endurance at normal cruise: 3.7 hr
Stalling speed clean: 88 kt
Stalling speed gear/flaps down: 78 kt
Turbulent-air penetration speed: 183 kt

piper-pa31t-ld

Piper PA-31T Cheyenne II / T-1020 / T-1040

 

 


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