Piper’s Impressive Cheyenne III

Piper’s Impressive Cheyenne III

Piper’s Impressive Cheyenne III

When Piper Aircraft announced its plans to build a big-cabin turboprop in late 1977, time was of the essence – only, we didn’t know it. It took another three years to get the airplane certificated, during which time the robust state of the general aviation manufacturing economy had begun to unravel. The Cheyenne III’s main competition, the Beech Super King Air 200, introduced in 1974, had an established head start, and industry sales volume was no longer the rising road to riches during the 1980s that it had been in the 1970s.

The Cheyenne III, and its successor, the IIIA, is a good airplane, and had times been better, its fortunes would have risen with its capabilities. The smaller Cheyennes had established an enviable reputation as fast, good-value business transports. The T-tailed PA-42 was an even-better rendition of Piper’s formula.

SPECIFICATIONS

Piper PA-42-720 Cheyenne III

Powerplants

Pratt & Whitney Canada PT6A-41, 720 shp

Seats

9-11

Fuel

560 usable gallons

Performance

Certified ceiling

33,000 ft.

Single-engine ceiling

18,200 ft.

Max. cruise speed

290 kts

Stall speed

87 kts

Takeoff distance
(50 ft. obstacle)

3,230 ft.

Landing distance
(50 ft. obstacle)

3,017 ft.

Max. range (w/reserve)

2,240 nm

Climb rate-2 engines

2,236 fpm

Climb rate-1 engine

531 fpm

Weights

Ramp

11,285 lb

MTOW

11,200 lb

Zero Fuel

9,150 lb

Landing

10,330 lb

Empty

6,389 std., 7,118 as tested

Useful load

4,896 std., 4,167 as tested

Dimensions

Wingspan

47.67 ft.

Height

14.75 ft.

Length

43.39 ft.

Cabin length

218 in.

Cabin width

49 in.

Cabin height

51.4 in.

Baggage

800 lb

The idea behind the Cheyenne III was fairly straightforward; take the Cheyenne II and make the fuselage almost nine feet longer, give it five feet more wingspan, with bigger engines, and top it off with a trendy T-tail. It would be able to hold up to eleven, have a max cruise of 290 knots and reach 33,000 feet for 1,500 miles of range. More of a winner is always better.

The engines would remain P&W PT6A turbines, but they would be the –41 versions with 100 more shaft horsepower than the –28’s of the Cheyenne II. More importantly, the engine would be flat-rated at 720 shp to about 16,000 feet, versus a max rating of 850 shp in Beech’s Super King Air, leaving the Cheyenne III some extra breathing room for high-and-hot performance.

A Purposeful Presence

As it appeared in early 1980, the PA-42-720 Cheyenne III conveyed an impressive ramp image. It has a long and lean look, with a huge tail and pencil-slim nacelles extending almost half the length of the fuselage. The horizontal tail spans nearly 22 feet and the maingear is 19 feet wide.

Some 88 Cheyenne IIIs were delivered before an engine change to the PT6A-61 created the Cheyenne IIIA in 1984. Power rating remained 720 shp, but with even more enhanced altitude performance. Around 60 of the IIIAs were built before production ceased after 1991; in addition to the free-fall of new general aviation aircraft sales, the PA-42-720 faced internal competition in the early 1980s from the introduction of the stretched Cheyenne IIXL in 1981, and then the Cheyenne IV (later known as the 400LS), which was built from 1984 to 1991. Also certificated as a PA-42, the hotrod IV had 1,000-hp Garrett TPE-331 turboprops and could reach 41,000 feet and top 330 knots.

IMG_1851Had the times been better, the Cheyenne III would have doubtless earned a good share of the twin turboprop market, as did the smaller Cheyennes. In 1979, U.S. aircraft shipments totaled 17,811 units; a decade later, in 1989, the industry built only 1,585 aircraft, and in 1991 the total was down to 1,021. The good times were over.

As a used aircraft, the Cheyenne III is a strong, capable business plane, even if its operation is often limited to 27,000 feet by today’s RVSM requirements. To experience the aircraft in flight, we were fortunate to accompany Roger Hines, partner and pilot at U.S. Assets Recovery, which operates a 1981 PA-42-720 as a company aircraft on business missions around the country. Centrally based in Joplin, Missouri, U.S. Assets flies to destinations ranging out 1,000 miles. Acquired about six months prior to our visit, the aircraft had accumulated about 7,500 hours total airframe time and had 2,000 hours on the engines, which came to the present owners with fresh hot section inspections. The paint job was applied in 2006, at which time the engines were upgraded to –42 status.

CRW_0797_RJPreflight Walkaround

The PA-42 series shares only fuselage cross-section and outer wing panels with the PA-31T, and a walkaround reveals many of its significant features. The nosegear strut holds a pair of landing and taxi lights, but the recognition lights in the nose of the wingtip fuel tanks can be illuminated at any speed. The landing gear is hydraulically-powered from engine-driven pumps, backed up by a nitrogen-charged blow-down system. The four-section wing flaps are electrically operated. A large 300-pound capacity baggage compartment in the nose is reached through a door on the left side; environmental components occupy the right side of the nose. A lead-acid battery, instead of the original ni-cad unit, was also in the nose.

Additional baggage, up to 300 pounds, can be carried in the aft cabin, and there are also nacelle lockers available, aft of the engines. Most Cheyenne IIIs have the optional nacelle fuel tanks, which limit locker storage to 100 pounds each. The fuel system is a series of ten interconnected cells and wingtip tanks; the nacelle filler ports must not be opened with more than two inches of fuel in the tip tanks, which would invite an overflow of Jet-A. Total usable capacity for the subject aircraft was 560 gallons. A total of nine drains are under the wings. No fuel tank management is required in normal operation.

The Cheyenne III’s engines are located 30 inches farther outboard than the smaller Cheyenne’s engines, creating a much quieter cockpit and cabin. An oil-cooler “cowl flap” is under each nacelle. The eight-foot diameter three-blade Hartzell propellers are fitted with “Q-tip” 90-degree bends at the ends of their blades, adding virtual diameter without extra noise.

IMG_1847The entrance door at the left rear of the cabin has three foldout steps, lowered into place via a pneumatic snubber, securely pinned against the 6.3 psi maximum pressure differential. An emergency exit surrounds the second cabin window on the right side. A swing-up supplemental cargo door aft of the airstair permits access to the aft baggage area without dragging luggage up the steps.

The massive empennage is pneu-matically de-iced, as are the wings, and the heated windshields are fitted with wipers, operable up to 153 knots. In addition to the dorsal fin, a small ventral fin is under the aft fuselage. The dual elevator trim tabs have redundant actuators. A trim tab is also fitted to the rudder and right aileron.

In the cabin, the forward club seating was supplemented by an aft forward-facing seat on the right side, along with the curtained lavatory seat in the rear. As is common, the left aft seat, next to the door, had been removed for easier boarding. Foldaway worktables and storage cabinetry facilitate inflight business dealing. Stepping over the massive main wing spar to reach the cockpit, some twisting is required to negotiate the floor-mounted yokes; the smaller Cheyennes used the Navajo’s through-the-panel control wheels. There are no storm windows on the Cheyenne III’s cockpit side windows.

Once settled, the cockpit is handily arranged, with fuel and emergency landing gear controls under floor covers. Trim wheels are on the lower pedestal, along with the Collins autopilot head. Most circuit breakers are on the right sidewall, with electrical switches and engine-start controls mounted in the overhead to give more panel space, the bane of bifocal wearers. A 40-light annunciator array is under the glareshield.

Of the 1981 avionics, only the Collins FD-112V flight director, dual RMIs, and Bendix RDR-1100 radar remained. Sandel SN330B electronic HSIs were in the pilot and copilot panels, and Garmin GNS-530 and GNS-430 units in the mid-panel were supported by a GMX-200 multi-function display. The twin rows of six turbine power gauges are mounted to the left of the avionics and the environmental controls are on the right subpanel.

IMG_1848Getting Underway

Starting follows the usual PT6A procedure, with a battery check and pushing the gear lever down; after starting, it will pop back up to a down-neutral position, verifying hydraulic pump operation. When shutting down, the procedure is repeated in reverse with the opposite engine running. Fuel is introduced as 12-14% N2 is reached and the ITT is monitored to not exceed the 1,000-degree C. start limit. Normal operation is limited to 750 degrees ITT.

Once the first engine’s generator comes on to restore battery condition, the second engine follows in due course at low idle. Avionics up, it’s time to taxi. Nosegear steering is positive and beta range holds taxi speed down to spare the brakes. Pretakeoff checks include the normal governors testing at 1,600 rpm, a flap-comparison test button is pushed, and there’s a “q-system” test, a simple sensor that inhibits gear retraction and pressurization engaging until 100 knots airspeed is reached. Yaw damper and prop synchrophasing are off and the oil cooler doors are open.

In position, torque is brought up to achieve prop governing at 2,000 rpm, then brakes are released to feed in 1,800 ft/lbs torque, building to 1,900 on the roll. Rotation is initiated at 105 knots, slightly above the Vmc of 97 knots, and Vyse is in hand at 115 knots. Gear retraction is to be done prior to 151 knots; best rate of climb comes at a very steep 118 knots, so most climbs are done at 160 knots, with prop rpm tweaked back to 1,900 or 1,800. Climb rate initially was 1,600 fpm at 130 knots, with a takeoff weight of about 10,700 pounds.

Climb rate out of 21,000 feet was still 1,100 fpm, where the torque had faded to 1,550 pounds. Leveled at FL250, torque was down to 1,400 pounds with the props pulled back to 1,700 rpm for even quieter operation; the IAS built to 172 knots, for a TAS of 265, using 270 pph of fuel per side. The cabin held at a comfortable 6,500 feet. Thanks to the 30-inches farther outboard engine location, the noise level was much lower than in the smaller Cheyennes. In fact, it was so quiet we eschewed headsets when we tried out the cabin environment; the prop and wind noise was a gentle hum.

The Cheyenne III’s cabin seats six comfortably.
The Cheyenne III’s cabin seats six comfortably.

The day’s trip was a 422 n.mi. run to Chicago Executive airport at Prospect Heights, Illinois, and with a 100-knot tailwind the scenery passed quickly. Layered conditions required the RNAV 16 approach at PWK, but the venerable automatic flight control system coupled nicely and we were soon maneuvering straight-in at 130 knots. The first 10-degrees of flap can be extended at 195 knots and gear can go out at 173 knots, so the Cheyenne III can keep up with fast traffic. Additional flaps are allowed below 151 knots. Shooting for 111 knots on short final, the landing was smooth and turnoff came in 3,000 feet.

On approach to Chicago Executive Airport.
On approach to Chicago Executive Airport.

In general, we found the Cheyenne III to be a very capable performer and much easier to fly than the smaller PA-31 derivatives, thanks to its long fuselage and large tail. It’s honest and straightforward, ready to do a good job in the middle altitudes. It’s too bad the market collapse came as it was just hitting its stride.

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