Pilot report - Piper Cheyenne 400LS

[Reprinted from Fliteguide / Imperial Aviation]

There is little doubt that Piper's PA-42 Cheyenne 400LS is the hot rod of the executive turbine fraternity. Indeed, the 1980 Cheyenne, which was launched with a pair of Pratt & Whitney PT6A-41 engines, was supposed to be a direct competitor to the staid Beechcraft King Air 200.

The Cheyenne 400 is that rare exception to the compromises required in aircraft design. It is an aeroplane that does everything well. It uses less runway, climbs and cruises faster than many pure jets. It carries more and further and does it all for about half the cost of a comparable bizjet. If the design has died with the old Piper Aircraft Company, general aviation may be immeasurably poorer.

Piper is a strange company. For ninety-five percent of the time the company limited itself to producing conservative if not down right boring aircraft. However, like the archetypal nerd in an action movie, the company would, completely out of character, do something either outrageous or brilliant or both. One famous such move was to call in Ed Swearingen to develop the Twin Comanche. Another and even more dramatic aberration must have given rise to the big Cheyennes.

The continual struggles to remain afloat at Piper can be attributed to their failure to develop a range of business jets which may have been largely immune to the light aircraft market vagaries wrought over by legal hyenas and their pursuit of product liability claims. Back in 1970, the then Cessna Chairman, Dwane Wallace, bet the future of the company on the then new Citation. Instead of competing with Cessna by developing a pure jet, Piper chose to leap ahead of Cessna by developing the PA-42 - essentially a turboprop-powered Navajo. Original PA-31T Cheyennes used PT6A-28 versions of the turbine engine. The aircraft was basically a re-engined piston pressurised PA-31P Navajo. The aircraft first flew in October 1969. Deliveries began in early 1974 - a long time after the King Air was launched.

The Cheyenne represented good value for money, especially when comparing to a King Air and the aircraft met with real market success. Encouraged, Piper continued to develop the model into the much larger T-tailed Cheyenne III, which first flew in 1979. With a cruise speed of 300 knots, the aircraft was already a high performance turboprop and was faster than everything else in its class except Mitsubishi's MU-2. There were many happy faces at Piper's Vero Beach factory where the Cheyennes were built. Then, the company had a further rush of ingenuity and hacked off the nice PT6s and in their place grafted on a pair of 1,650shp Garrett TPE-331 dash fourteens. These engines lacked the polite whine of a free-turbine, instead beckoning operators with the high-pitched scream of its fixed shaft Garretts. To many, this installation appeared to be an overkill, particularly when the huge propellers needed to harness the power, were added to the nacelles. In the Cheyenne 400LS, the Garretts have been reigned in to a flat rating of just 1,000shp - but they will deliver this power all the way to Flight Level 200!

The result is astonishing. The 400LS will out climb most small to medium business jets. In terms of hard numbers, it has a maximum true airspeed of 360 knots and will cruise at over 40,000 feet at 340 knots for nearly seven hours. It will accomplish this seating nine people in stretch-out comfort and at less than half the fuel burn of a Citation II. Because high altitude performance is so important to speed and fuel efficiency, the 400LS's ability to get to altitude quickly is vital, particularly on short sector lengths of 150 nautical miles or so. The cabin pressure differential is a relatively high 7.6lbs, giving an 8,000 feet cabin at the certified maximum altitude of 41,000 feet. Single-engine ceiling is a Mount Everest-topping 29,000 feet - what more could you want?

Less than 50 Cheyenne 400s were made before production terminated in 1992. I had been invited to fly South Africa's only example, ZS-PHO, a 1985 model. Compared to other business aircraft, the 400LS looks sleek and rakish.

The dominating features are the pair of broad Dowty Rotol propellers (whose diameter is the same as the chassis length of a long wheel base Land Rover). Although the undercarriage legs have been strengthened and lengthened, the props are huge paddle-blades with a ground clearance of a meagre eight inches. Studying the Pilot's manual shows that this is clearly a problem. Apart from the inevitable abrasion these blades will suffer when used on dirt airstrips, the clearance has important implications during ground handling. An STC has reportedly been approved for five bladed scimitar propellers from Hartzell, which apart from improving ground clearance, will increase the maximum speed by a remarkable 60 knots to well over 400 knots!

During the pre-flight walk about it is clear this is a Piper and not a Beechcraft product. PHO's age is beginning to show in the general fit of the panels and particularly on the fibreglass mouldings, which were beginning to craze. The heavily over-engineered solidity of Beech products seems to be lacking, most obviously when looking at the access panels which appear to be loose fitting. When checking the Garretts it is necessary to open a small hatch in each engine to examine the chip and fuel filter sensors. If they have been triggered and won't reset they are no-go items.

To accomodate the additional power of the engines under asymmetric conditions, the vertical tail has been enlarged so that, despite the aeroplane's low slung stance, the tail is higher than a King Air 90's. Handling is enhanced through counter-rotating engines. Access to the cabin is via a gas strut-supported airstair door behind the port wing. Front seat access is not the best due to the narrow cabin cross section and dominating centre pedestal. Once seated, the front office is very comfortable and the panel layout good with the pilot's side containg two EFIS screens. In the centre of the panel is an 18-inch colour radar screen and information on all three tubes can be interchanged should any of them fail. Hidden modestly in the airspeed indicator is a Mach meter!

The start sequence is fully automated. With 24 volts required, the pumps are turned on and the starter button is pressed. At 13% Ng, the engines light off and attention must then be shifted to the EGTs. These are redlined at 820 degrees C and it is necessary to have fingers poised over the fuel cut-off buttons should the temperatures exceed the 820 limit. In general, the only time this limit should be in danger of being exceeded is when the batteries are not fully charged or the aircraft is pointing downwind. Wind blowing straight down the large tailpipe makes it harder for the heat to disperse. The Garretts have sophisticated protection systems built in. Torque limiters protect the engines from injudicious applications of power and there are built in data recorders. These flag hot starts and other out of limits parameters as well as taking vital signs every time you push the button. This helps to maintain the engines on an on-condition basis.

With the post start checks complete, it was apparent the engines produce a high level of residual thrust, even at flight idle as the aeroplane was straining to move forwards. Taxiing is straightforward and with the checks complete we lined up on Lanseria's runway 06. Standard operating procedure is to then power up to 30 percent torque against the brakes. Apparently, any power setting above this will start sliding the tyres. The reason for this maximum 30 percent power setting becomes apparent from reading the last page of the manual under: 'Tips for operators'. The problem is essentially that of propeller clearance. As the power is increased, the nose wheel oleo compresses and clearance decreases.

The aircraft is not the easiest to keep straight on the centre line. However, as speed built up, so lateral stability improved and we were very quickly at rotation speed where a firm rearwards application of the column had the aircraft off the runway and heading up at an amazing rate of climb. At all phases of flight, the cabin noise was less than I remember it being in other turboprops. Piper's advertising blurb claims it is quieter than the business class section of a Boeing 727. The cabin is so well insulated, this claim might be true.

Holding the column with my left hand, I tried a gentle turn and was surprised by the heavy controls. My first instinct was to check the autopilot wasn't on.

The stiff controls help to make the Cheyenne appear stable in all phases of flight but it was like trying to drive a car with the power steering switched off. Checking longitudal stability, I pushed the nose down initially with one hand and then two. With a 5 degree nose down attitude, I released the column and the nose obediently rose to the horizon and then beyond. It happily went into a 700 feet per minute climb. I didn't wait for the aeroplane to settle back to its cruise attitude, as it seemed the Cheyenne would continue to climb until it went orbital. A steep turn required a firm rearwards input on the column, but once established in the turn, the aircraft felt rock steady. Roll rate was fair.

Being the sophisticated high performance aircraft that it is, the Cheyenne 400 is equipped with a stick shaker and pusher as well as a yaw damper. The flying characteristics at the stall are therefore academic as the stall is defined by the pusher forcing the nose down rather than the airflow breaking away from the wing. Better to see how the aircraft performed in the circuit. Turning for home I made an obvious mistake. I simply put the nose down. In a piston this is fine, it gets you home quickly and keeps the engines warm - but not in the Cheyenne. This is an aircraft that, thanks to its huge abundance of power, operates close to its redline Vmo speed as a matter of routine. Putting the nose down simply sent the airspeed round to the wrong side of the striped barber's pole at an indicated 270 knots indicated. I quickly pulled the power back to just 30 percent and even so we were in danger of exceeding the 250 knot speed limit drawing close to Lanseria.

The gear came out at 170 knots and then I made my second mistake by underestimating the space needed to make the final approach turn. After an inadvertent hammerhead I managed to hit 130 knots before applying full flap.. This brought the speed back to 125 knots or blue line, until crossing the fence at 110 knots. Due to the heavy controls, the aircraft needs to be correctly trimmed and fortunately trim input is minor during the final approach.

Pulling the power all the way back over the threshold, I needn't have worried about the highly loaded wing giving up flying suddenly. I held the nose up and waited for the Cheyenne to settle gently onto the runway. This is an aeroplane that floats thanks to its long low wing and residual thrust. Eventually the wheels touched in an almost level attitude, with the nosewheel following soon after the mains.

It is recommended that once the mains have contact, the nosewheel be lowered immediately and held down to stop the aeroplane from jumping back into the sky. The Cheyenne 400 loves to fly.

I applied power and lifted the flaps for the go-around. Backpressure on the column gave an easy rotation despite our relatively forward C of G. The aircraft needed no forward input on the column following rotation unlike most T-tailed aircraft. On the crosswind leg, I pulled the power back to avoid busting the 6,000-foot turbine altitude circuit limit. Extending the downwind leg to accommodate slower traffic, I had plenty of time to configure the aircraft for another approach and made a rather better job of the second landing. Once down, the selection of beta mode was enough to slow us down quickly but comfortably without having to use reverse. With the big engines and propellers, reverse thrust has the ability to pile all the passengers up against the crew seats.

Back on the apron, we allowed the engines to idle for a few minutes to stabilise temperatures before holding the props against the beta stops and cutting the fuel supply. I was very impressed with the 400LS and we chatted with the owner for a long time about this impressive aeroplane and its capabilities. The huge power of this Piper has made this not just a hot rod special of limited utility but an aircraft of immense practical use. It is capable of taking as many people as a Citation I a far greater distance at a similar speed. The owner says that on a Lanseria to Luanda leg, the aircraft can carry more payload than a King Air 200. With 2,000lbs of fuel for four hours there is still capacity for another 2,200 lbs of passengers. Typical fuel burn at a high cruise level is 400lbs (60 US gallons) an hour - half that of a comparable Citation. With total useable fuel of 570 gallons, the aircraft can comfortably make Johannesburg to Mauritius non-stop.

Even compared to the original 'bionic budgie', the Boeing 737, the Cheyenne performs well. The Boeing takes about 18 minutes at gross weight to climb to flight level 330, the Cheyenne will climb to flight level 350 in just 16 minutes! In the hands of Chuck Yeager, the Cheyenne 400 holds all the time-to-climb records in its class. A Citation II takes six minutes longer than the Cheyenne to get to flight level 350. This means the 400LS gets to cruise speeds and low fuel burn rates quicker than pure jets and very much cheaper.

In conclusion, while Piper may have lost the race for pre-eminence in the construction of general aviation aircraft, they lost despite having some excellent products, despite the unlikelihood of ever seeing Piper rejoin the big business multi market again.


Note: PlaneCheck often has some nice Cheyenne 400s for sale