Turbine Pilot: New Beginnings

PiperJet repositions a legendary company

December 1, 2008

The PiperJet represents a new beginning for 71-year-old Piper Aircraft, according to company officials. The single-engine very light jet (VLJ) is Piper’s first turbofan product, and interest in the unusual design has spurred new attention for the entire product line. Piper President and CEO James Bass notes that although total piston aircraft sales were down 16 percent across the industry in the first three quarters of the year, Piper’s deliveries of piston airplanes were up 18 percent. “We are a new company fueled by a venerable heritage,” Bass said at a ceremony this fall shortly after the jet’s first flight. “We truly are the inheritors of a great legacy, and we are inspired by the knowledge that our best days are ahead of us.”

With its 44-foot wingspan, including winglets, and single tail-mounted Williams FJ44-3AP engine, the PiperJet is unlike anything Piper has ever built—yet from a profile view you can see the heritage of the Aerostar, Cheyenne, Meridian, and Navajo product lines in the square windows and fuselage shape. With its projected 360-knot cruise speed, the PiperJet will be among the fastest in the VLJ category. Although the Cirrus and Diamond single-engine VLJs will be certified to 25,000 feet, the PiperJet will be certified to 35,000 feet. Eclipse plans to certify its Model 400 to 41,000 feet.

The PiperJet proof-of-concept (POC) airplane made its first flight in late July. Two conforming flight test airplanes will join the certification effort starting in about a year, along with a static test airframe and a fatigue test article. Piper expects to certify the airplane and begin deliveries in late 2011 or early 2012, about a year later than the original schedule announced in 2006. Bass said the company has funded the $25 million program so far with working capital, deposits, and private investment. All in all, Piper will need about $100 million to complete the project, some of which will come from outside investors.

The company has 200 orders for the $2.199 million jet, 50 of which have been retailed by dealers. Bass said he believes there is a market for about 400 VLJs per year and that Piper should be able to hold a 25-percent market share. Its business plan calls for between 75 and 100 PiperJets per year—all of them to the owner-flown market. “If other types of ownership occur, that’s great,” Bass said. Already speculating on future products, Bass said the PiperJet is designed to be modular, meaning that it can grow or contract.

It flies

Vice President of Sales Bob Kromer described how a flight might go: The pilot starts the Williams engine with the push of a button, allowing the full-authority digital engine controls to bring the engine online. The engine is capable of 3,000 pounds of thrust, but Piper will de-rate it to 2,490 lbst, providing extra climb performance at high altitudes. The proof-of-concept airplane has a direct-link nosegear steering system and straight main gear. Production airplanes will have trailing-link main gear, which should please pilots and passengers. The cabin can be configured with four passenger seats in a club configuration and a large aft baggage compartment; space just behind the cockpit and opposite the airstair door is reserved for storage, an optional forward-facing seventh seat, or an optional enclosable lavatory. The integrated cockpit will house Garmin products. Piper has not yet announced details of the Garmin system, but it will likely be an outgrowth of the current G1000 system. Flight control is through a sidestick, freeing space in front of the pilot. An autothrottle system will be optional.

Maximum takeoff weight is projected to be 7,250 pounds with a standard empty weight of 4,100 pounds. Piper is guaranteeing a full-fuel payload for a standard-equipped airplane of 800 pounds, a maximum range of 1,300 nm, and a 360-knot maximum cruise speed.

A typical takeoff will use 15 degrees of flaps with a rotation speed of 80 knots. Initial climb rates exceed 3,400 feet per minute on the POC airplane. Best angle and best rate of climb speeds will be 160 and 180 KIAS, respectively. Normal climb is 200 KIAS. The POC is still climbing at 1,000 fpm at FL350. Piper projects the airplane will be able to fly 1,000 nm at its max cruise of 360 KTAS with IFR reserves—burning 77 gph. At a long-range cruise of 320 KTAS, IFR range stretches to 1,300 nm on 64 gph. The cabin will remain at sea level pressure through 18,000 feet. At 35,000 feet the cabin will settle in at 8,000 feet—a 7.45-psi cabin differential. VMO/MMO will be 250 KIAS/Mach 0.65.

Kromer said the engineers and test pilots predicted the high thrust line of the engine might require some sort of automatic elevator trim augmentation system with thrust changes. However, initial flight tests and more than 1,000 wind tunnel tests show the required trim changes to be more benign than expected, perhaps eliminating the need for the augmentation system. Kromer predicted that the cabin will be exceptionally quiet because the single engine is mounted so far aft of the passengers. Visibility from the cockpit is excellent, with the wing well behind the pilots. The tail-mounted engine reduces concerns about foreign object debris damage and eliminates concerns about injuring ramp personnel and damaging ground equipment behind the airplane. And, he noted, the single engine reduces exterior noise and emissions, an ever-increasing concern.

The airplane will be certified for flight into known icing conditions, using pneumatic boots on the wings and tail and bleed air to protect the engine inlet.

On approach, the gear and initial flaps can be lowered at 200 KIAS. Flaps 20 degrees come out at 160 KIAS and flaps 36 degrees at 130 KIAS. VREF for a typical landing weight will be 80 to 85 KIAS with a touchdown at about 70 knots. The PiperJet will meet the mandatory 61-knot stall speed. Landing distance at typical weights will be about 2,500 feet. Antiskid brakes will be optional.

Piper plans to develop a pilot training program with an outside partner to be named later.

After months of considering various alternatives, Piper plans to build the airplane at its Vero Beach, Florida, headquarters. The natural laminar flow wing is assembled using the latest metal bonding techniques, giving it a smooth, nearly rivetless surface.

Bass describes the PiperJet’s look as “distinctive.” Others have described it as resembling a mini-McDonnell Douglas MD-11 because of the straight, tail-mounted engine. It is unique in GA. When one shows up on your ramp in a couple of years, you will have no doubt that it is a PiperJet—an airplane that “marks the beginning of a new era for Piper Aircraft,” according to Bass.

E-mail the author at thomas.haines@aopa.org .

What It Looks Like: Behind that shroud

Windshield bleed air anti-ice

By Mark R. Twombly

Turbine-powered aircraft are time machines—as in saving time that owners and operators can put to more productive use than long hours spent traveling via other means. To fulfill that time-saving mission, turbine-powered airplanes must have the performance and equipment to operate in almost any kind of weather, including icing conditions. It’s never a good idea to loiter in ice-producing clouds or precipitation—no matter how capable and equipped the airplane—but sometimes climbing or descending though weather, perhaps on departure or approach, is unavoidable.

If you’ve flown piston-powered aircraft with known-ice certification, you’re probably familiar with the “hot plate,” a small, rectangular-shaped electrically heated windshield element that rests on the outside of the left-side windshield to give the pilot at least a limited forward view in icing conditions. Fortunately, turbine-powered aircraft have more effective windshield anti-ice systems than the old hot plate.

One way to prevent ice from forming (anti-ice) on windshields is by directing hot engine bleed air over the windshield. The Cessna Citation 500 series relies on this method. (Many other turbine aircraft have electrically heated windshields.) It sounds simple enough—borrow some hot air from the compressor section of the engine to lay down a layer of heated air over the outside of the windshield—but in fact the system is fairly complicated. Major components include a cockpit bleed-air switch that activates a bleed-air control valve, a heat exchanger, automatic temperature controls, temperature and pressure sensors and annunciators, manual flow control valves, and discharge nozzles.

To activate the system, the pilot positions a Windshield (W/S) Bleed Air switch in either the High or Low position, depending on ambient temperature. (Select High when ambient temperature is below minus 18 degrees Celsius, Low when above minus 18 degrees C. The rule of thumb is to use High when above flight level 180, and Low below.) This opens the bleed-air control valve, allowing engine bleed air to flow into an air-to-air heat exchanger located in the aft fuselage. The automatic temperature controller manipulates an air control valve in the heat exchanger to maintain the downstream bleed air at approximately 138 degrees C when the W/S Bleed switch is on the High setting, and about 127 degrees C when on Low.

The second action required of the crew is to turn a pair of Windshield Bleed Air controls clockwise, which opens valves in the windshield bleed air ducting to allow the air to flow to discharge nozzles located at the outside base of the windshield behind prominent shrouds.

The Citation checklist calls for activation of the windshield bleed air system on descent regardless of ambient conditions, but many pilots elect to use it only if icing conditions are expected. That’s because, over time, the hot bleed air can degrade the base of the plastic windshield.

Should something fail in the windshield bleed air system rendering it unusable, the pilot can use a back-up alcohol system for anti-ice protection. An electric pump pulls alcohol from a half-gallon reservoir located in the nose baggage compartment and discharges it through a six-tube spray nozzle positioned at the base of the pilot’s windshield only.

A full reservoir is good for about 10 minutes of continuous operation of the system, which means the pilot’s first priority is to find a way out of icing conditions.