Gulfstream raises the bar with G650

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Manufacturer launches biggest business jet, the all-new G650, and sets its sights on being the fastest and furthest-flying

Its model number is G650, a new top-of-the-range Gulfstream, but the type certificate will say GVI, the sixth generation in a legendary family. New Gulfstreams are not everyday occurrences, appearing once a decade since the GI flew in 1958, and the G650 will be the first with an all-new type certificate since the GII.

"This is a clean-sheet aircraft. It will not replace the G550," says Gulfstream president Joe Lombardo. "It is in a different market segment." Compared with the G550, the new aircraft has a longer, wider fuselage bigger, high-speed wing fly-by-wire controls and more powerful engines.

It is not supersonic, and it is not composite, but Gulfstream believes the G650 may be as big as a purposed-designed business jet can get. "Gulfstream customers say they like to see more size, range and speed," says Pres Henne, senior vice-president programmes, engineering and test. "So we have responded with the biggest, furthest and fastest."

Further and faster

The G650 will have longer range and higher speed than any other purpose-designed business jet: 12,950km (7,000nm) at Mach 0.85, 9,250km at M0.90 and a maximum cruise speed of M0.925. That is further and faster than Bombardier's Global Express XRS and will outrun Cessna's M0.92 Citation X.

Gulfstream says the G650 will have the largest cabin in its class. The cross-section is taller and wider than the G550's, and essentially identical to the Global Express's. Overall, the cabin has 28% more volume and 30% more floor area that the G550's, plus 11% more baggage volume.

The G650's maximum gross weight is just under the 45,360kg (100,000lb) limit set by New York's Teterboro airport, a key business aviation hub, to keep out airliner-sized aircraft. Gulfstream believes other airports will adopt this cap, making 100,000lb the de facto limit for business jets.

Overall, the G650 is a relatively modest scale up from the G550: 3,900kg higher maximum take-off weight 1,300kg more fuel in a 13% bigger wing just over 1m longer with just under 2m more span and 4.6% more take-off thrust from the Rolls-Royce BR725 engines. But Gulfstream is claiming substantial improvements in aerodynamic efficiency from the new high-speed wing.

Although it looks like previous Gulfstream wings - characteristically clean, with no leading-edge devices and no flap tracks - the planform and aerofoils are new. Area is increased 13% for lift, span 1.83m for drag and quarter-chord sweep 6˚ for speed. Compared with the G550, "the wing is 8% more efficient and Mach 0.055 faster," says Henne. "We got the peak efficiency out to M0.855, and think this aircraft will be used in the M0.90 range a lot."

Like previous Gulfstreams, the G650 has a metal airframe. "It's not a composite fuselage," says Henne. "There's still a lot of learning going on so we stuck with a metallic structure." Composites are used in the horizontal tail and rudder, winglets, cabin floor, aft bulkhead and various fairings and doors.

The fuselage uses bonded panels, enabling automated assembly. Coupled with increased use of machined parts, this has dramatically cut parts count. "We aimed for 50% parts reduction, and beat our target," says Henne.

Gulfstream started out intending to replace the G550, but as the design evolved the decision was taken to build the G650 alongside the G450/G550. This required construction of a new manufacturing facility at the Savannah, Georgia plant, but allowed Gulfstream to plan a new assembly line taking full advantage of three-dimensional design tools.

"The rate of G550 production will be dictated by the market. We expect to build it until we replace it with some other model," says Lombardo. Henne, meanwhile, acknowledges the G650 is the first in a new family.

Gulfstream will share the $1 billion development bill with risk-sharing partners. These include Spirit AeroSystems for the wing and engine nacelles and Fokker for the empennage and fuselage panels. Other supplier parters include Honeywell (avionics, auxiliary power unit and environmental control system) GE Aviation Systems (secondary power) Goodrich (landing gear) and Meggitt (brakes).

Fly-by-wire

Gulfstream has assembled a team of partners to supply its first fly-by-wire system. The three-axis digital system has two flight-control computers, each with two channels for quadruplex redundancy. The electrohydrostatic actuators are powered by two hydraulic systems, one less than in the G550. A three-axis backup flight control unit with independent hardware and software provides a "get home" capability via electric back-up hydrostatic actuators. Each has a self-contained electrically powered hydraulic system. Thales is supplying the computers and Parker the actuators. Rockwell Collins is providing pilot controls and trim system and Moog the flap system.

The benefits of FBW, says Henne, include consistent handling qualities, enhanced stability and both low-speed and high-speed envelope protection. Gulfstream has retained the traditional control wheel and column, in part because it is aiming for a common type rating with the G550. But Henne also believes sidesticks do not yet provide the required crew coordination and awareness of autopilot inputs. "We were pushing for an active sidestick, but it's not there yet," he says. "And a passive sidestick is a step back in awareness."

Based on Honeywell's Primus Epic avionics, the G650 cockpit is an evolution of the PlaneView integrated flightdeck fitted as standard across Gulfstream's large-cabin jets. In addition to four large-format liquid crystal displays, the next-generation PlaneView II includes the recently certificated synthetic vision primary flight display and latest EVS II enhanced vision system. But it also features a new Collins LCD head-up display and Honeywell three-dimensional weather radar. Gulfstream has developed a combined display controller and standby instrument that is mounted on the glareshield.

Other PlaneView II enhancements include required navigation performance, controller-pilot datalink and GPS precision approach capability. Gulfstream already has enhancements in the pipeline for synthetic vision -which presents a synthesised image of the outside world on the PFD. These include range grids, extended centrelines and runway markings, says Henne.

But the G650 was fundamentally designed around its cabin. The choice of width was a "technical and emotional issue" that ended in a compromise between the leadership of Gulfstream and its parent company, General Dynamics, Henne says. The cross-section is not circular. "We used the floor as structure and played around with the cross-section to get in what we wanted while minimising wetted area," he says. The bottom is flattened to reduce surface area and drag.

The signature oval windows are retained but are 16% larger, located higher in the fuselage, spaced further apart to increase seat pitch and there are two more per side for a total of 16. To meet the latest certification requirements, there are two new overwing exits per side, each larger than the window they incorporate. The main entry door is larger, and Gulfstream has lowered the tail slightly to bring the aft baggage door closer to the ground for easier loading.

A significant advance hailed by Gulfstream is its "Cabin Essential" design philososphy, which requires that no single-point failures results in a loss of functionality. This has been achieved through redundancy in the waste, water, light, power and other cabin services. "We think this will be a tremendous advantage to the traveller," says Henne.

First flight of the G650 is planned for the second half of 2009, leading to US and Euro­pean certification in 2011 and entry into service in 2012. Five aircraft, including the first two production G650s equipped with interiors, will be used in the 18-month, 1,800h test programme.

Price for 2012 delivery is $58.5 million, rising to $59.5 million for aircraft delivered from 2013. The new facility has the capacity to build 90 aircraft a year on two lines, but will begin at 35-45 a year. Gulfstream will start taking orders in April. "We have a feeling this will be a very profitable aeroplane," says Lombardo.