The G650 is 's first completely clean-sheet large-cabin aircraft since the Gulfstream II debuted in 1967, and consequently the business aviation community has high expectations for it. The Savannah, Ga., firm was compelled to set higher goals for its new flagship — and its possible derivatives — than for previous generations of large-cabin Gulfstream jets. After all, the competition from 's and 's upcoming super jets is considerably stronger than that which existed back in the bell-bottom and Oldsmobile era.
To raise the bar ever higher, the G650 is designed to fly nearly 30 kt. faster at long-range cruise than the current production G550 and to beat the latter's class-leading range by 250 mi. The newest Gulfstream also has been upgraded with digital flight controls, similar to those of the Falcon 7X, and, most importantly, it has a new, non-circular cabin cross-section that's wider and taller than that of the Bombardier Global 6000, formerly the heavy iron leader in cabin comfort. The G650's cabin cross-section also will be larger than that of Bombardier's uber-jets now in development, the Global 7000 and 8000.
, Gulfstream's parent company, strongly believes long-range, large-cabin business jets will sell well in coming years, so starting with the G650, Gulfstream is investing substantially in product development. The G650 presumably will be morphed into shorter- and longer-range derivative aircraft, some perhaps with shorter and longer cabins. All are likely to share the G650's four-radii, flattened oval fuselage cross-section and signature wide-oval windows. The new Gulfstreams should help the Savannah firm to counter the potential threats posed by Dassault's upcoming 5,000+ nm range, large-cabin SMS twin, as well as the Global 7000 and 8000, along with other competitive models that might emerge.
Clean-sheet product development is only one of the sea changes occurring at Gulfstream. The firm also is investing heavily to upgrade its manufacturing processes with the goal of slashing the G650's parts count by one-half with a concomitant reduction in assembly hours. Labor-intensive manufacturing long has been eating into Gulfstream's profits because legacy Gulfstream large-cabin aircraft are hand built much the same as older top-tier British and Italian luxury cars. The final result of these auto and airplane hand-manufacturing processes was near perfection, but at a staggering cost in labor hours.
That's all changing with the G650. The new 200,000-sq.-ft., two-line G650 production plant is eerily quiet, not unlike a modern automobile assembly plant. There are very few workers on the shop floor and a paucity of hand labor tasks, such as fitting, trimming, drilling and riveting. For instance, rather than mechanical fasteners, metal bonding is used to attach longerons to most fuselage skin sections. Single piece parts, formed from solid billets by computer-controlled high-speed mills, are replacing parts assemblies that used to be handcrafted out of dozens of little plates, fillets and brackets. On the shop floor, clecos are almost as rare as cigarettes.
Most of the heavy machining, milling and manufacturing is done outside the Savannah plant. Large subassemblies built by third-party manufacturers and Gulfstream's own outside facilities arrive at the Savannah plant where giant overhead gantry cranes and precision alignment trolleys move them into position with a 0.015-in. tolerance for joining on the parallel assembly lines. Computer-controlled, multi-axis machine tools install many of the fasteners to complete the green airframes, thereby eliminating thousands of hand-labor tasks.
Elsewhere at Savannah, the changes in process are no less impressive. Gulfstream's R & D campus at the northwest corner of the airport has doubled in size. General Dynamics is making available technical resources from other divisions to Gulfstream, including Electric Boat, builder of some of the quietest submarines ever to submerge. If you know how to make silent a “Boomer” at 100 fathoms, it's no sweat to quash noise emitters in a business aircraft. Using their submarine acoustical tool kits, Electric Boat's hush-hush mavens cut the G650's interior noise by 5 to 6 dB compared to the G550, which is one of the quietest business aircraft in production.
The technology wrapped up into the G650 is head and shoulders above anything Gulfstream ever embraced in developing its previous jets. The deeper one delves, the more one appreciates the design details.
Structure, Aerodynamics and Systems
Gulfstream's customers dictated the terms of the G650's design. Overwhelmingly, they favored a go-slow approach toward embracing new technologies, especially composite airframe construction. Accordingly, the G650's primary airframe structure, including the fuselage pressure vessel and wings, is made of high-strength aluminum alloys, augmented with steel, stainless steel and titanium, similar to previous Gulfstream aircraft. However, more composites are used in the G650 than in earlier Gulfstreams, including the horizontal stabilizer, elevators and rudder, plus floorboards, rear pressure bulkhead, engine nacelles, winglets and various fairings, among other secondary structures.
Fuselage frames are evenly spaced at 17.5-in. intervals, wider than that on previous Gulfstreams. The design change makes room for longer-spaced cabin windows. That also increases legroom in the seating groups because seat placement is based upon window spacing. The windows also are larger, visually complementing the larger fuselage cross-section.
Structural efficiency also is improved. While the aircraft has a larger fuselage cross-section than the G550, it has about the same weight per linear foot, plus it has considerably higher pressurization. But green aircraft empty weight goes up by more than 5,000 lb. because of the new aircraft's 3.3-ft.-longer fuselage, larger wing, engines and empennage, among other factors.
Aerodynamically, the G650 leaps ahead of previous Gulfstream large-body jets. The nose has been completely recontoured to reduce shock-wave drag. The windshields and side windows are much larger than on legacy large-cabin Gulfstreams, greatly improving outward visibility.
As with its previous large-cabin models, Gulfstream elected not to fit the G650 with leading edge slats because its engineers believed the additional weight and complexity did not offset the improvement in high angle-of-attack (AOA) lift. Instead they fitted the aircraft with a 1,283-sq.-ft. wing that results in the lowest wing loading of any ultra-long-range business aircraft. This results in acceptably low takeoff and landing speeds.
The wing also has 33 deg. of sweep at quarter chord to reduce Mach-induced drag. Large, outwardly canted, highly swept, blended radius winglets will help reduce wingtip vortices, an important design feature considering the wing's modest 7.73:1 aspect ratio. The airfoil thus is optimized for Mach 0.855 cruise, which is Mach 0.055 higher than the G550's airfoil. It also generates 8% more peak lift at cruise speed. The G650 is the first large-cabin Gulfstream to have an area ruled aft fuselage to reduce high-speed interference drag between the engine nacelles and fuselage. That's a drag cheating technique long used by Bombardier and Dassault on their large-cabin aircraft to lower the local Mach number in that section of the airframe.
The result is an aircraft that can cruise 7,000 nm at Mach 0.85+ and 6,000 nm at Mach 0.90. It also consumes less fuel while cruising at Mach 0.85 or better than any other large-cabin aircraft in current production. It can fly nonstop from San Diego to Sydney, Chicago to Cape Town or even Hamburg to Hawaii at long-range cruise. The G650 is the first purpose-built business jet that can fly from New York to Tokyo, Seoul or Beijing in well above ISA conditions, even with less than optimum routing and ATC climb clearances.
Most G550 systems are carried over but have been updated to improve redundancy, simplicity and reliability. The electrical system, for instance, has many more backups because of the aircraft's digital fly-by-wire (FBW) control system and electrically powered backup flight control hydraulic system.
To start, two engine-driven 40 KVA constant-speed generators and a 40 KVA APU generator supply 115/200 VAC, three-phase, 400 Hz current mainly for motors, heaters and battery chargers. A 15 KVA ram air turbine has been fitted to the aircraft to provide a fourth source of emergency AC power.
Most of the 115 VAC is converted to 28 VDC by five transformer rectifier boxes for use by other equipment. The two battery chargers also can function as transformer rectifiers under certain conditions. Two 28 VDC, 53 AH nicad main batteries supply power for APU starting, operating the auxiliary hydraulic pump, and left and right essential buses if no other DC power is available. There are two 24 VDC, 9 AH nicad emergency batteries, plus uninterruptible power supply and backup flight control hydraulic power pack emergency batteries. Notably, Gulfstream initially announced that the G650 would use lithium-ion batteries, but the development team abandoned that plan in late 2011 when the candidate batteries failed to meet performance requirements. Nicads add about 150 lb. to empty aircraft weight, compared with lithium-ion batteries.
There are comparatively few mechanical circuit breakers in the overhead panel and in the left and right electrical equipment racks just aft of the cockpit. Most AC and DC circuits are controlled by electronic circuit breakers hosted by the secondary power distribution system (SPDS), accessible by means of the MCDUs in the center console. The SPDS eliminates 3 mi. of wiring, 400 mechanical circuit breakers and 300 lb. of system weight.
All interior and exterior lights are LEDs, with the exception of the high intensity discharge (HID) xenon landing lights. Gulfstream developed a proprietary landing light pulsing system for the HID bulbs that makes the aircraft easier to spot by other aircraft and birds.
All fuel is carried in the left and right wet wing tanks. A heated fuel recirculation system prevents fuel gelling during long, high-altitude missions. DC-powered main and alternate pumps in each wing provide positive fuel pressure to the engine-driven pumps. The single-point pressure refueling system has a refuel quantity preselect feature that may be controlled by either the standby multifunction controller in the glareshield or external ground service control panel near the right wing leading edge. Improved fuel distribution and balancing slashes refueling time to 26 min., a 19-min. improvement compared with the G550's upload time. The aircraft also may be refueled by means of overwing gravity ports, but doing so reduces total refuel quantity by 550 lb.
Gulfstream engineered a five-channel FBW flight control system for the G650 having left- and right-side, dual-channel flight control computers, plus a backup flight control unit, for the aircraft. FBW saves 100 lb. of weight and makes it much easier to rig flight control surfaces, and offers more redundancy than a conventional hydromechanical flight control system. FBW also eliminates control cables, pulleys and linkages in the aft equipment bay, greatly improving preflight access to other systems. The G650 thus becomes the first Gulfstream to have fully powered flight controls rather than boosted controls.
Electrical power sources include the two main generators, the APU and the RAT, along with two main, two emergency, singleand single backup flight control batteries. With five control channels and 10 power sources, there's actually a great deal more redundancy in the flight control system than with traditional hydromechanical control links.
Conventional control yokes and rudder pedals in the cockpit, supplied by, have five signal transducers that send commands to the four flight control computer (FCC) channels and the backup flight control unit (BFCU) built by Canada. Any one of the five channels can command movement of all flight control actuators. The two FCCs or BFCU, in turn, send command information out to remote electronic units, furnished by Parker Aerospace, that command the movements of each flight control actuator.
Each FCC has one active and monitoring channel. It's as though two airplanes were flying in tight formation with one pilot flying and one pilot monitoring aboard each airplane. Thus these four pilots in the two airplanes and all four channels in the two FCCs are different, but they all have to agree on a course of action. The BFCU, though, “flies” solo. It's only there in case the other two FCCs are completely unavailable.
There are four primary flight control modes, three of which are hosted by the dual FCCs. Normal mode, using inertial and air data inputs in addition to pilot commands, provides flight envelope protection, maneuver and dynamic rudder load alleviation, and stability augmentation, including a speed stability function. Stability augmentation includes automatic compensation for pitching moments induced by changes in flap, landing gear or speed brake configuration. Gust load alleviation, thrust asymmetry compensation and P-Beta yaw/roll coupling compensation are not built into the control laws.
Direct law, rather than more complex pitch rate command law, is used for takeoff and landing. Up and away, the primary high-level pitch control law is Nz, or vertical acceleration, command with “U” speed stability, meaning the pilot has to trim pitch for speed changes. Theand 787 and also use similar FBW speed stability control laws.
Certain sensor or communications malfunctions cause the FCCs to revert to alternate law mode. Most high-level FCC control law functions are retained, but envelope protection and the autopilot are not available. In addition, stall warning stick shaker is activated at a lower angle of attack. And Vmo, Mmo and crosswind limits are reduced.
If so many sensors and/or malfunctions make alternate law unavailable, then the FCCs revert to direct law. All high-level control law functions are lost, including automatic actuation of the speed brakes and ground spoilers. Control inputs from the pilots to the yoke, rudder, speed brake handle and trim switches directly result in control surface movement.
Finally, if all functionality of both FCCs were to be lost, there is a backup flight control computer that provides complete control, but all high-level control law functions are lost.
The G650 is the first large-cabin Gulfstream to have a fully trimmable horizontal stabilizer. Inputs to the normal or backup pitch trim switches send signals to command movement of the horizontal stab. Pitch trim commands, though, may be sent to the elevator during certain phases of flight. The horizontal stabilizer then is automatically trimmed by the FCCs to relieve the load on the elevator.
The roll trim switch on the center console repositions the neutral point of the control wheel, commanding movement of the ailerons and spoilers. However, moving the rudder trim switch only commands movement of the control surface, not the rudder pedals. An “auto center” button in the console provides a convenient way to center the rudder, such as on short final.
The aircraft has simple, four-position, slotted, trailing edge Fowler flaps. Multifunction spoilers, with three panels on each wing, provide roll augmentation, air brake and ground spoiler functions.
The G650 retains the dual hydraulic system architecture of its predecessors, although it has FBW flight controls with no mechanical links between the cockpit and the control surfaces. Most aircraft with fully powered flight controls, be they traditional hydromechanical or FBW systems, require three separate hydraulic systems in order to provide the required redundancy.
Gulfstream's innovative approach, which enabled the G650 to retain the dual 3,000-psi hydraulic circuit design, involves using remotely located, DC-powered packs in hybrid flight control actuators. Seven of the 16 flight control actuators can function either as conventional electrohydraulic actuators or as DC electrically powered actuators in the event of the loss of normal left or right hydraulic pressure. Gulfstream calls these components electric backup hydrostatic actuators, EBHAs for short. The EBHAs can power the ailerons, elevators and rudder, along with the outboard spoilers, thereby providing the redundancy, but not the weight or complexity, of a third hydraulic system.
There'stype certification pre–cedence for the dual hydraulic, electric power pack backup design approach. uses a similar architecture on its super-jumbo and military airlifter, but the electrohydraulic actuators work full-time instead of just being backups.
Aboard the G650, both left and right 3,000-psi hydraulic systems are powered by engine-driven pumps most of the time. The left side does most of the heavy lifting, including powering part of the flight controls, as well as the landing gear, flaps, nosewheel steering and inboard brakes, plus on-side thrust reverser. If the left engine-driven pump is inoperative, a DC auxiliary pump or a right-to-left power transfer unit also can power the left side. The right hydraulic system powers part of the flight controls, along with the outboard brakes and on-side thrust reverser.
The main landing gear employs a trailing link design for smooth touchdowns. The brake-by-wire system has both brake temperature and tire pressure monitoring through the EICAS. However, there is no auto-brake function. The nose gear has a digital steer-by-wire with up to 7 deg. of authority through the rudder pedals and up to 80 deg. of authority with the tiller, depending upon groundspeed. If the tiller sensor fails, nosewheel steering authority through the rudders increases to 16 deg. Notably, the nosewheel steering links do not have to be disconnected for towing.
Bleed air is used for wing leading edge and engine cowl anti-ice protection, cabin pressurization and air-conditioning, along with main engine starting and for sucking ambient air through the total air temperature probe. The APU, an external cart or the cross-side engine can supply air for starting a main engine. The APU supplies more bleed air than both engines at idle thrust, so it's advisable to turn off the bleed air from the main engines and use the APU to supply the twin air-cycle machine packs during ground operations in warm weather. In addition, engine ground idle rpm is reduced with the bleeds off, thus there's less residual thrust and reduced need to use the brakes while taxiing.
The interior has three-zone temperature control, with one thermostat in the cockpit and two at opposite ends of the passenger cabin. Chilled air also is used to cool the forward electrical equipment racks. Maximum pressurization is 10.69 psid, so typical cabin altitudes range from 3,000 ft. at FL 410 to 4,850 ft. at FL 510.
The G650 has a fully MSG-3 maintenance friendly design with 600-hr. basic inspection intervals.
Upgraded Passenger Comfort
The G650's passenger cabin is 14-in. wider, 3-in. higher and substantially longer than that of the G550. Finished dimensions are 8.2 ft. wide, 6.3 ft. tall and 42.9 ft. overall length from cockpit divider to the baggage compartment bulkhead. The floor is a full 15-in. wider than the G550's, making it the widest among purpose-built business aircraft. The aircraft's new four radii cross-section was inspired by the non-circular design of G150, one that maximizes head, shoulder and elbow room for the available cross-section. The G650 has 28% more total cabin volume and 30% more floor area, along with 3 in. more legroom in each seating area than the G550. Gulfstream's signature wide oval windows are 16% larger and 3.4-in. higher for better viewing. The 16 cabin windows are by far the largest of any business jet. Yet, the linear weight of the fuselage pressure vessel is essentially the same as that of the G550. That's impressive structural efficiency, considering the aircraft has the highest pressurization of any current production ultra-long-range aircraft.
The G650 has the first electrically controlled and latched door in an FAR Part 25 aircraft. It's 6.3 ft. high by 3.0 ft. wide with an air-stair design having illuminated treads, sturdy left and right hand rails and an offset hinge that increases headroom when entering the vestibule. There is no manual door handle, other than a maintenance door release buried behind the cover. Electric locking and unlocking, along with electric actuation, enables the flight attendant or the flight crew to open or shut the door from their crew stations.
The aircraft has 27.5-in.-long left and 33.5-in.-long right electrical equipment racks in the forward cabin. Gulfstream engineers elected to retain the above-floor equipment bays rather than move the equipment under the floorboards because they say the bays provide better equipment cooling and much easier maintenance access to components for technicians.
A dozen pre-set “Select” interior configurations are available for the G650. The aircraft we flew for this report had the Universal 13 layout, featuring forward crew area with crew rest compartment, galley and lavatory, three seating areas in the main cabin, an aft lavatory and an internally accessible baggage compartment beyond that. The fit and finish of Gulfstream's interior furnishings and completion work are superb.
On the right side of the crew area, there is a hanging storage closet for the crew and an 80.4-in.-long crew rest compartment with solid, sound attenuating pocket door, a cabin window and a berthable 24-in.-wide chair. Ahead of the chair, there is a 22-in.-long by 24-in.-wide foldout worktable that stores in the side panel and a 17-in. entertainment monitor on the forward bulkhead. A JetBed collapsible mattress is required equipment to configure the chair as a qualified crew berth in accordance with Part 135.
Aft of the entry door, there is another 11-in.-wide hanging closet and a 51-in.-long left-side crew lavatory with solid pocket door, window, mirror with indirect lighting, storage compartments and vacuum toilet. With the cushion cover folded down over the potty, the crew lav doubles as an additional seated rest area for a crewmember.
Next aft, there is a 52.5-in.-long galley that is split into left and right halves, each of which has a window. The left side has a wet sink with water sterilizer and counter space with pullout work surface, two beverage pots, microwave oven and convection oven in a stainless-steel faced stack, along with tableware storage, plus a dirty dish drawer and waste bin. The right side has an overhead stemware rack, 10-bottle wine rack, two ice drawers, a 4.5-cu.-ft. refrigerator/freezer and storage drawers. The forward end of the galley may be shut off from the lavatory and crew rest compartment with an accordion curtain. The aft side of the galley has an electrically operated pocket door to separate the compartment from the 26.7-ft.-long main seating area.
The main seating area is quite similar to that of the G550, but each of the three sections is appreciably longer, wider and taller. Each section has a pair of windows with electric shades, universal 115 VAC/60 Hz power outlets, headphone jacks and PDA charging docks. There also is a 115 VAC/60 Hz external power connection to provide ground power for a cabin vacuum cleaner and passenger systems.
On the right front bulkhead, there is a 26-in. LCD entertainment system monitor. The front section has a four-seat club section with the aft two seats being electrically powered with back and seat cushion heat, electric lumbar control and back cushion massage. The chairs are 28 in. wide overall with 21 in. net width between the armrests. Electrically actuated, left- and right-side, 28-in.-long by 29-in.-wide foldout worktables extend from and retract into side panels at the touch of a button. Pairs of facing chairs convert into sleeping berths. Electrically powered and heated chairs may be installed at other locations, but each adds about 30 lb. of weight to the aircraft. Also, 12.1-in. personal entertainment monitors are available as options.
The center section has a left-side, 45-in.-wide, four-seat conference grouping with power outlets, HDMI video port and RJ11 satcom phone jack. On the right side, there is a 7.1-ft.-long credenza that houses a 26-in., electrically actuated, pop-up LCD monitor, office equipment and chilled wine rack. Each 18-in.-wide chair can be tracked 9 in. fore and aft. The aisle side chairs track inboard 5 in. for additional elbowroom. A 32-in.-long by 45-in.-wide foldout conference table between the facing chairs extends and retracts on telescoping legs. The four-seat conference grouping converts into a double bed.
Also in the center section, there are twin, left- and right-side overwing emergency exits that are similar to those in early Gulfstream jets, but they're considerably larger. Rather than simply being removable windows, the four new emergency exits are 2.2-ft.-high by 2.7-ft.-wide doors in the fuselage walls with integral windows in their centers. The change more than doubles the size of the emergency exit openings compared to those on the G550.
The aft section of the cabin has an 80-in.-long three-place divan on the right side with a 3.95-cu.-ft. storage cabinet at the front and a first-aid cabinet at the rear. There are two facing chairs on the left side that convert into a single berth. So, the aircraft sleeps six passengers on overnight trips. The aft section may be enclosed with bulkheads, converting it into a private stateroom.
Aft of the main seating section, there is a 48-in.-long lavatory with vacuum toilet and 13-in.-wide closet on the left and wet sink plus vanity cabinet on the right. The lavatory has no windows.
The back side of the lavatory is a secondary pressure bulkhead with access door to the 195-cu.-ft., 2,500-lb. capacity aft baggage compartment. The compartment is 11% larger in volume than that of the G550. Inflight access is restricted to FL 400 and below, thus it's practically only accessible during climb-out and descent. The 3.6-ft.-wide by 2.6-ft.-high exterior door is 8% larger than on the G550 and the sill height is 4 in. lower for easier loading.
Left Seat in the G650
We belted into the cockpit of serial number 6013 on an afternoon in late January with G650 project test pilot Jake Howard in the right seat and senior experimental test pilot Tom Horne in the jump seat as safety pilot. The aircraft's BOW was 54,372 lb., giving it a potential 1,428-lb. full fuel payload. Gulfstream quoted the BOW at 54,000 lb. for BCA's May 2012 Purchase Planning Handbook. Early G650 operators say their aircraft actually weigh between 54,400 lb. and 54,922 lb., chock full of optional equipment and fully provisioned for long transoceanic missions with multiple meals. Thus, they only can carry four to seven passengers with full fuel. Each additional passenger, however, only costs about 35 nm of range.
Many of the G650's operating protocols, systems procedures and flow patterns are carried over from the G550. Gulfstream had hoped G550-qualified pilots would be able to use a common type rating for flying the G650. However, theand EASA nixed that plan because the G650 has much less in common with the G550 than initially meets the eye, such as FBW flight controls, the secondary power distribution system and standby multifunction controllers (SMCs), among other significant changes.
Most checklists for the G650 are completed using “flow and verify” protocols, splitting responsibilities between left- and right-seat pilots shortly after starting the APU. The left seater flows the overhead panel, including running the systems tests, followed by sweeping from the left side panel, control yoke, left SMC, flight guidance panel and to the center console. The right seater only has to check the onside SMC, control yoke and right-side panel items and equipment.
As noted, the cockpit has much improved outward visibility because of its considerably larger windows. In addition, the EVS camera has been moved up close to the base of the windshield center post, thereby reducing parallax errors when using the EVS HUD imagery as an aid for taxiing at night or in low visibility conditions.
Fuel on board for our flight was only 15,600 lb., but it was enough to fly from Savannah to San Diego or Gander at Mach 0.85 and land with NBAA IFR reserves. Horne computed the ramp weight with safety pilot and other equipment at 70,022 lb., or about 70% of maximum ramp weight. Savannah's field elevation is 50 ft. OAT was 25C. Computed takeoff speeds were 108 KIAS for V1, 109 KIAS for rotation and 126 for the V2 one engine inoperative takeoff safety speed. En route OEI climb speed was 147 KIAS. TOFL was 3,400 ft.
Engine start was very similar to that with the G550. Switch on the boost pumps, turn on the start master and press a start button. With oil pressure and indication of fan rpm, turn on the fuel cock. The FADEC handles the rest. We noted that the air cycle machine packs automatically shut down during engine start to assure sufficient bleed air from the APU to turn the twinBR725s' air turbine starters. After start, the ACMs automatically come back on line.
After we completed the post-start checks, we rolled out of the chocks with very little thrust. Indeed, we needed to extend a thrust reverser from time to time to control taxi speed without riding the brakes. Howard pointed out that turning off the engine bleed air and using the APU for the packs causes a drop in engine ground idle rpm, thus reducing idle thrust.
Holding short of Runway 19, Howard ran through the pre-takeoff checklist and checked the flight controls for proper movement on the MFD flight controls page. Taxiing on to the runway, Howard armed the ground spoilers before we advanced the throttles, thereby causing them to pop up. Only by keeping one of the throttles slightly advanced above the idle stop could we make the ground spoilers retract. This functionality is carried over from legacy large-cabin Gulfstreams and seemed somewhat antiquated. We'd prefer to see the system updated with ground speed sensing so that the spoilers would pop up until the aircraft reaches a reasonable initial takeoff roll speed.
With a takeoff weight of about 69,600 lb. and 37,800 lb. of thrust, acceleration was sporty, even by Gulfstream standards. Shortly after rotation, the aircraft left the runway in about 3,000 ft. Control response was crisp and the aircraft was well damped in pitch, no doubt due in large part to the 36.6-ft. span, 439-sq.-ft. horizontal stabilizer that provides considerably more pitch control authority compared to those on the G450 or G550. But the high-level FBW control laws surely played a significant role as well in the G650's well-mannered behavior.
The aircraft also had pleasant artificial roll control feel and good roll response with adequate control yoke centering, but very little on-center breakout force. Engineers with Gulfstream and Rockwell Collins, which supplied the control yokes and rudder pedals, worked together closely to fine tune artificial feel and control response. Quite candidly, your fingertips might tell you this is a $200 million FBWeven though the data plate says it's a Gulfstream.
The aircraft exhibited excellent short-period stability in all three axes, but it's difficult to tell how much was contributed by natural aerodynamics versus high-level FBW control laws. On the way up to initial cruise altitude, we had a couple of intermediate level-offs required by ATC and comparatively sharp turns. Yet, using a 250 KIAS/260 KIAS/Mach 0.85 climb schedule in mostly ISA conditions, the aircraft leveled off at FL 470 in 23 min. At ISA-7C, it cruised at Mach 0.85 or 480 KTAS on 2,400 pph at a weight of 67,500 lb.
Then we pushed up the throttles because high-speed cruise is the G650's forte. The 67,400-lb. aircraft smartly accelerated to Mach 0.90, resulting in 506 KTAS on 3,000 pph in ISA-7C conditions. There is only a 1.5-2.0 dB increase in cabin noise when cruising at Mach 0.90 instead of Mach 0.85 long-range cruise, Gulfstream claims. Horne also noted that the cabin altitude only was 4,300 ft.
We couldn't perform our usual long-period (phugoid) pitch stability check because the FBW system masks the natural, high-Mach aerodynamic stability characteristics of the aircraft. But we did check Mach buffet margins. A wind-up turn indicated the aircraft has robust high-speed buffet margins, albeit at a comparatively light weight. We didn't encounter buffet until about 1.4 g at Mach 0.88 in a 45-deg. turn.
Then we descended to FL 430, using idle thrust and speed brakes. We noticed only mild buffeting and a slight pitch change when the speed brakes were extended. Once level at that flight level, we again pushed up the thrust to check how fast the aircraft would cruise. Horne reported the cabin altitude was 3,380 ft.
As for speed, the G650 did not disappoint. At max cruise thrust, it accelerated to its Mach 0.925 redline at a weight of 67,000 lb. while burning 4,100 pph. Some operators doubtlessly will dash across North America or the North Atlantic at 530 KTAS or faster depending upon OAT. But BCA estimates that maximum range will be cut to 5,000 nm or less at that speed.
Down at 15,000 ft., we flew a series of standard air work maneuvers. Steep turns are easy to fly. The HUD's flight path vector (FPV) and velocity trend vector provide precision guidance cues. Stick force is moderately heavy, but that's appropriate for this class of aircraft. We also flew clean and dirty stalls, at least to the maximum AOA permitted by the FBW control laws.
We used a clean configuration for the first stall. At a weight of 66,800 lb., we trimmed the aircraft for a 156 KIAS Vref speed or 0.67 normalized AOA, reduced thrust and decelerated. “Normalized” means that 1.0 AOA is the maximum lift coefficient adjusted for high-lift configuration and local Mach number because of its influence on buffet and stall. At 15,000 ft., though, the effect of local Mach number on the wing is insignificant.
The pitch limit indicator appeared on the PFD and HUD at 0.75% maximum normalized AOA. During the approach to clean stall, the stall-warning stick shaker fired at 129 KIAS or 0.94 normalized AOA. At 0.97 AOA, the FBW system limited elevator and horizontal stabilizer pitch control authority to prevent untoward handling characteristics. Holding the control wheel full aft, the nose thus gently pitched down and we initiated recovery.
The dirty stall, with gear down and flaps extended to the full 39 deg., was equally non-dramatic. We trimmed for 122 KIAS or 0.67 AOA, commenced a normal glidepath-like descent and then leveled off without adding thrust, thus allowing the aircraft to decelerate. After the stick shaker fired, we continued to pull aft on the yoke until reaching the stops. At 0.98 normalized AOA, the nose gently dropped and we initiated recovery with only a slight loss of altitude.
The two maneuvers quite clearly demonstrated the G650's improvement in high AOA behavior compared to previous generations of large-cabin Gulfstreams. If both stick shaker and stick pusher are ignored in some of the legacy Gulfstream models, positive stick force gradient can be neutralized or even reversed. Stall recovery thus becomes much more challenging and there can be a substantial loss of altitude.
Returning to Savannah, we prepared for a WAAS LPV precision approach to Runway 19. Horne computed Vref at 120 KIAS for a 65,500-lb. landing weight and a non-factored landing distance at 2,873 ft. based upon 13-kt. headwinds. It's apparent that the G650's ref speeds at typical landing weights will be similar to those of the G550, even though it is a heavier airplane with more wing sweep.
We bugged the target airspeed at 125 KIAS and let the auto throttles maintain speed in gusting wind conditions. The G650's big airfoil with low wing loading doesn't provide as smooth a ride in turbulence as the more highly loaded airfoils of competitors' aircraft. But it does enable the aircraft to cruise higher where the air generally is smoother for most of the mission.
The HUD's azimuth and glidepath guidance cues, along with the FPV marker, made it easy to hand-fly the approach. We noted that the airport database used by the HUD needs a little updating. The synthetic runway outline displayed was 2 deg. right of the actual pavement borders. In addition, runway touchdown elevation and glideslope/glidepath data must be manually entered through the standby multifunction controller because the HUD isn't fully integrated with the FMS airport database.
The FBW system transitions from high level control law to direct law for takeoff and landing, so the G650's smooth handling behavior during approach reflects its aerodynamic refinement. At 50 ft., we pulled back the thrust to idle and continued to use the HUD until touchdown. The aircraft appears to float less than the G550, but touchdown behavior was nonetheless very smooth. We deployed the thrust reversers, but kept the throttles at idle, thereby allowing the aircraft to decelerate leisurely. A light touch of the brakes and we turned off at Taxiway B1 after a touchdown roll of about 5,200 ft.
Our standard profile calls next for a simulated one-engine inoperative takeoff and landing. But we previously performed those maneuvers in the G650 simulator at FlightSafety International's Savannah training center. This both reduced risk and added the realism of a complete engine failure rather than by reducing thrust to idle in the actual aircraft. Rudder pedal forces on the OEI takeoff were moderate and the aircraft was easy to control. For landing, though, we couldn't use the auto throttle because the system only works if both engines are operating. Managing the asymmetric thrust, however, wasn't much of a challenge. We appreciated the addition of the automatic rudder center function because it eliminates the need to retrim the rudder to neutral or hold rudder pressure during the flare.
The second takeoff in the actual aircraft on Runway 19 thus was a normal all-engine maneuver to a downwind VFR pattern. Downwind, we slowed to 180 KIAS, extended the flaps to 10 deg. and lowered the landing gear. Abeam the approach end, we started a shallow descent and extended the downwind leg. Turning base, we extended flaps to 20 deg. and slowed to 160 KIAS. We turned to a 3-mi. final while extending the flaps to 39 deg.
We aligned the 3-deg. nose-down pitch mark on the HUD with the runway touchdown zone and used the FPV to maintain desired trajectory. The technique worked well, but we flared with a touch too much speed causing a little float. Make a note. Aircraft with no leading edge devices tend to float more than those with slats if you carry excess speed.
We again turned off after a 5,000-ft. landing roll and taxied back to the Gulfstream ramp. Pulling into the chocks, Howard turned on the belly videocam and displayed the image on the MFD. This enabled us to track the parking alignment line within a couple of inches of centerline, shutting down the engines after the 1.7-hr. demo mission.
Conclusions? The G650 is the nicest flying large-cabin Gulfstream yet built. The fly-by-wire functionality is all but transparent unless probing the extremes of the flight envelope. Pilots might not know it's an FBW aircraft without being told. PlaneView II, the HUD and EVS, among advanced cockpit features provide unsurpassed situational awareness in the cockpit. The cabin environment, including increased volume, window size and pressurization, along with the redundancy and reliability of Gulfstream's Cabin Essential CMS, make it the most commodious and functional business aircraft yet built by the Savannah firm.
Price and Value
Travel time savings is the prime justification for operating a business aircraft. Each new Gulfstream model, starting with the transcontinental GII in 1967, has been at the head of its speed and range class when introduced. That was true for the GIII in 1980, GIV in 1987 and GV in 1997.
Being able to cruise at Mach 0.80 may have been the benchmark in the 20th century, but it seems slow by 21st century standards. Even long-haul airliners now can cruise at Mach 0.85. Bombardier indeed routinely quotes Mach 0.82 to 0.85 as the normal cruise speed for its current production Global series business jets.
The G650 now sets a new standard with its Mach 0.90 high-speed cruise and 6,000-nm range. Slow down to Mach 0.85 and it leads the ultra-long-range class with 7,000-nm range. Assuming standard day conditions, the aircraft can depart a 4,000-ft. runway and fly eight passengers 4,000 nm in just over 8 hr.
The aircraft also tops the class with the highest pressurization, largest windows and lowest sound levels. The accompanying BCA Comparison Profile, however, pro–vides a somewhat skewed picture of the aircraft's overall capabilities primarily because of the inclusion of the Boeing BBJ1 and Airbus ACJ319. Having a large maximum payload capacity, for instance, is important if you're hauling large groups of affiliated travelers, such as sports teams or heads of state with full entourage. Most competitors also can carry more payload with max fuel than the G650 and their maximum payload to MTOW ratio is higher, again biased by the inclusion of the Boeing and Airbus transports.
The number of people who can be accommodated in full-flat berths with full fuel may be a more useful measure of utility in a long-range business aircraft. On overnight missions, the G650 and most purpose-built business jets can sleep six. Converted airliners typically sleep no more than 10 in full-flat berths.
Speed, range and fuel efficiency are the G650's strong suit, as shown by the Comparison Profile. Among purpose-built business jets, the G650 has the best fuel efficiency while cruising at Mach 0.85. If those same competitors slow down to their best long-range cruise speed, most are somewhat more fuel thrifty.
But what price is time? Cruising at Mach 0.85 instead of Mach 0.80 only saves 45 min. on a 6,000-nm trip. Speed up to Mach 0.90 and the travel time is shortened by one and one-half hours. On 7,000-nm trips, the time savings become more significant. The G650 can fly those trips nonstop in 14 hr., 42 min. All the competitors have to make a fuel stop, adding as much as an hour to travel time.
So, for now, the G650 is off to a healthy lead in the ultra-long-range business aircraft class. But Bombardier's Global 7000, promising 7,300-nm range at Mach 0.85, is due to arrive in 2016. The Montreal planemaker's 7,900-nm range Global 8000 will enter service just one year later. Longer term, Dassault could challenge the G650 with a growth version of its upcoming SMS.
In Savannah, though, no one is losing sleep over these potential airplane threats. The G650 is here and it's delivering on its promises. It's up to the competition to prove their claims, officials say. And Gulfstream already is studying its next generation of top-line business aircraft because its engineers believe you earn no points for finishing in second place. BCA
To watch our video pilot report of the Gulfstream G650, tap here in the digital edition of BCA, or go to AviationWeek.com/video
Gulfstream G650 Performance
These graphs are designed to illustrate the performance of the Gulfstream G650 under a variety of range, payload, speed and density altitude conditions. Gulfstream's sales engineers provided the data for all three charts, but estimated per–formance assumes ideal climb, cruise and descent profiles; direct routing; no ATC restrictions; and standard day conditions with no wind, among other factors that can alter actual aircraft performance. Keeping this mind, do not use these data for flight planning purposes.
|BCA Equipped Price||$65,000,000|
|Engine||2 RR BR700-725A1-12|
|Output/Flat Rating OAT°C||16,900 lb. ea./ ISA+15C|
|Payload With Max Fuel||1,458/661|
|Fuel With Max Payload||39,500/17,917|
|Fuel With Executive Payload||43,658/19,803|
|Time to FL 370||NA|
|FAR Part 25 OEI Rate (fpm/mpm)||1,511/461|
|FAR Part 25 OEI Gradient (ft./nm)||621/102|
|Sea Level Cabin||31,800/9,693|
|FAR/EASA Part 25, 2012|