Business & Commercial Aviation, December 2003

Gulfstream's 450 Surprise

Lots of folks were caught off guard when the G450, the next-generation GIV/G400, made its official debut on the eve of the 2003 NBAA Convention in Orlando.

By Fred George

Lots of folks were caught off guard when the G450, the next-generation GIV/G400, made its official debut on the eve of the 2003 NBAA Convention in Orlando. Gulfstream Aerospace succeeded in keeping the G450 Savannah's best-kept secret for more than five months following s.n. 4001's first flight on April 30. Serial numbers 4002, 4003 and 4004 also entered the flight-test program prior to the convention, putting the G450 on track for late 2004 FAA and European Aviation Safety Agency (EASA) certification and first customer deliveries in early 2005.

After years of anticipating when Gulfstream would introduce its next iteration of the best-selling Gulfstream ever, the company unveiled an aircraft that is essentially the same size, but does virtually everything better. The new G450 weighs less, flies farther and climbs higher at MTOW. It needs shorter runways on comparable length missions and it has considerably better hot-and-high airport performance. It gets better fuel economy and it has lower operating costs, less maintenance burden and more reliable systems.

Powering the new Gulfstream are two next-generation Rolls-Royce Tay 611-8C engines, featuring bigger fans, better hot section parts and FADECs. In addition, the aircraft has the G550's entire Honeywell Primus Epic PlaneView avionics suite, including its VGS head-up display and infrared EVS camera as standard equipment. In fact, the G450 combines a G550's whole nose section with the GIV/400 fuselage tube.

Some changes are obvious. From a distance, you can tell the difference between a G450 and a GIV/400 because the new model's composite construction, monochrome engine nacelles lack the older model's polished aluminum thrust reverser clamshells. Closer up, it's apparent that the main entry door has been moved aft 3 ft., freeing up almost one-third more volume in the cockpit. Pull a tape measure between nose and tail and you'll find the G450 is 1-ft. longer overall. With the main entry door being moved aft, a 12-in. plug was inserted just aft of the cabin door to preserve the same cabin dimensions as the GIV/400.

But you must look really closely at the G450, if not peel away its skin, to see most of the major changes. Beneath the familiar exterior shape, the G450 is more G550 than GIV/400. Its systems, control feel and procedures conventions are 99.9% GV/550, so G450 captains will need a GV/550 type rating to fly it instead of a GIV/400 endorsement on their tickets. Notably, some G450 systems actually are more advanced than those in place on current production G500 and G550 airplanes. Eventually, those improvements will be rolled back into the G550 and G550.

After we learned all this at the NBAA Convention, Bryan Moss, Gulfstream's president, asked B&CA for an opinion of the firm's latest heavy iron jet. “Don't know until we can fly it.” “I should have known that's what you'd say," Moss countered, suppressing a smile. After a short pause, he said, “Two weeks.” Fourteen days after NBAA closed in Orlando, we were off to Savannah.

Structure and Systems Upgrades

With a few exceptions, the G450 is a G550 with respect to systems architecture. From the onset, the G450 has been designed to comply with Maintenance Steering Group 3's guidance for ease of repair and inspection. “A'' checks, for example, will be extended to 500-hr. intervals and component access is far superior compared with GIV/400 series airplanes. Many bleed air valves have been relocated from the pylons to the engine compartments, providing quick access as soon as the cowl doors have been opened.

Overall, Gulfstream predicts a 10% to 20% reduction in direct hourly maintenance costs compared with GIV/400 series aircraft. The G450's airframe is mostly G400, with the G550 nose section grafted on the front of the fuselage. This affords pilots 30% more space in the cockpit, thereby increasing available legroom by about 1 foot. In contrast to the G400's relatively cramped cockpit, tall pilots in the G450 actually must track their seats forward to reach the rudder pedals.

The new cockpit configuration also increases storage space for navigation charts and flight bags in large part because the adjacent left- and right-side electric equipment bays, just aft of the cockpit/cabin divider, are much smaller than those on the GIV/400. Also, the G450 gets the G550's space-saver jump seat, which is easier to deploy and store.

The G550's improved nosewheel assembly and nosewheel steering system also is incorporated with the new nose section, as is the windshield rain removal blower that replaces the GIV/400 windshield wipers. The G550's large capacity emergency blow-down pneumatic bottle is installed as well. The G450 also gets the G550's heated cabin windows that eliminate the need for desiccant packs to prevent condensation between the panes.

While the G450's left and right electrical equipment bays are considerably smaller than those of GIV/400-series aircraft, moving the cabin door 3 ft. aft still would have resulted in less available cabin space for the passengers, thus the 12-in. plug in the fuselage. The G450 also will be fitted with a vacuum lav with a holding tank in the aft equipment bay and conformal water tanks in the baggage compartment to improve net usable luggage storage volume. The vacuum lav system eliminates the need to install a front lav servicing port if a forward lav is installed during completion.

The vertical fin is slightly taller to accommodate the G550 radome. This will enable the G450 to be outfitted with a variety of satcom and satellite television options. The change is typical of Gulfstream's push to “productionize'' as many systems and provisions for options as practical, so as to speed the completion process and improve reliability. Gulfstream officials say that it will take only 22 weeks to complete a G450 at one of its facilities.

During the past several months, the firm's flight test engineers flew several flow visualization tests during which colored dye was streamed from several tiny nozzles distributed from nose to tail. The slipstream deflected and dried the dye so that flow patterns could be studied after landing. As a result, the G450 is undergoing thorough aerodynamic fine-tuning that will help to increase its eight-passenger range 250 mi. over that of the G400. Sixty percent of the vortex generators, for example, are being eliminated and several are being relocated. VGs may be added on the bottoms of the engine nacelles in the vicinity of the flap trailing edge to help prevent shock-induced flow separation.

The leading edge of the wing, though aerodynamically unchanged, will be fabricated out of the same alloy used for the G550 to help prevent oxidation. Operators complained that the GIV-SP's leading edge aluminum had to be buffed frequently to maintain its shine. The G450, in green configuration, will weigh 500 lb. less than the G400. This mostly is achieved by fitting the aircraft with new lightweight composite nacelles fabricated by Vought Aircraft Industries and single-pivot thrust reversers made by the Nordam Group.

The PlaneView avionics suite that replaces the G400's SPZ-8400 avionics also helps reduce weight. Gulfstream's spec BOW for the G450 is 43,000 lb. But that's 900 lb. less than a typically equipped G400 — not 500 lb. less. As a result, the G450's typically equipped BOW may be closer to 43,400 lb., in B&CA's opinion.

Almost all the G450's upgrades were driven by GIV/400 series aircraft operator advisory group inputs. Their top ten gripes were addressed in the G450 makeover. Gulfstream folks claim there's almost no wire, line or duct that hasn't received careful scrutiny as a result of operator suggestions. The split bus electrical system, for instance, uses the GV/550's airline-proven, constant-speed, 400-Hz, 40-kVA integrated driven generators in place of the GIV/400's 30-kVA wild-frequency generators and trouble-prone Bendix AC/DC power converters. The APU also has a 40-kVA AC generator, one-third more power than the GIV/400's APU produces, and there is an emergency 10-kVA hydraulically powered generator available if all other AC power sources fail. A no-break power transfer system assures seamless transition from one AC power source to another without interruption. Four transformer rectifier units (TRUs) provide twice as much DC power as the Bendix power converters to the four main and essential DC busses. A fifth TRU powers the aux DC buss and is available as a backup to any one of the other four normal TRUs.

Starting power for the APU is provided by two lead-acid batteries in the aft equipment bay, or “ boiler room'' in Gulfstream parlance. The battery access doors on the left side of the aft fuselage have been eliminated, but a large, quick release door replaces them, thereby providing easy access to the APU for servicing. A G550-style winch will be installed on the boiler room ladder to hoist the batteries in and out of the airplane. Most of the “heavy lifting'' systems, such as windshield and probe heating, motors, battery chargers and external lights, are AC powered. DC power mainly is used for light duty and control functions, but it also powers the main and aux electrical fuel pumps, as well as the auxiliary hydraulic pump. The G450 is fitted with dual nav and strobe lights, preventing a critical single unit failure from grounding the aircraft prior to dispatch.

The 3,000-psi hydraulic system functionally is the same as the G400's equipment, but the power transfer unit that provides backup hydraulic power for the combined system and the aux hydraulic pump have been moved out of the main landing gear wheel well and into the boiler room to suppress noise in the main cabin when they're in operation. Pilots, please note. There's no longer an imaginary sign above the entrance to the flight deck that says “Now Entering Gold's Gym."

The boost ratios on the elevators and ailerons have been increased by one-third, providing the G450 with virtually the same control feel as the GV/500/550. In addition, the G450 has the G550's hard-over protection system (HOPS) that automatically isolates pitch, roll or yaw power control units (PCUs) from the hydraulic system in the event of a malfunction. If a hardover does occur, hydraulic power automatically is shut off only to the affected axis' PCUs. As a result, the manual, all-axis flight power shutoff valve has been eliminated. Moreover, the HOPS can be reset in flight by pulling and resetting the associated circuit breaker that controls the affected system.

The mechanical flap/stab interconnect linkage and “dwell box” in the boiler room have been eliminated. The G450 is fitted with an electronic interface unit that will require less maintenance and provide smoother pitch transitions between flap configurations. Gulfstream has replaced the GIV-SP's Dunlop brakes and analog anti-skid system with Aircraft Braking Systems Corp. (ABSC) carbon/carbon brakes and a digital anti-skid system. The replacement interval has been increased to 2,000 landings and Gulfstream test pilots report that performance from the new brakes during early FAR Part 25 maximum brake performance testing has exceeded expectations. The ABSC brakes also have improved temperature sensors for higher reliability.

Heating and cooling performance aboard the G450 has been substantially upgraded. The new Honeywell 36-150GIV APU produces 44% more bleed air and is routed through twin G550 air-conditioning packs in the boiler room. A new three-zone climate control system ensures comfort in the cockpit, forward cabin and aft cabin. In contrast, the refrigeration capability of the G400's lower capacity, two-zone system is taxed on the ground in extremely hot weather.

The G450's pressurization is slightly higher than the G400's system. As a result, the maximum cabin altitude is 6,000 ft., versus 6,500 ft., at FL 450. Down at the airplane's initial cruise altitude of FL 410, cabin altitude is 5,000 ft. The G550's passive door seal replaces the G400's pressure inflated door seal. The G550's large capacity, two-bottle supplemental oxygen system is installed, replacing the three-bottle system of the G-IV/400 series airplanes.

All the cockpit annunciator switches are illuminated by LEDs with 20,000-hr. MTBFs, making them much cooler to the touch. Flying the G450 Jake Howard, lead G450 flight-test engineering pilot, walked us around s.n. 4004 prior to the demonstration flight out of Savannah International (SAV), pointing out its various features and product improvements. When Howard started the Honeywell 36-150GIV APU, we were especially impressed with how much quieter it is, both inside and outside the aircraft, compared with the 36-100G fitted to GIV/400 series airplanes.

The mission of Flight 015 on s.n. 4004 was to evaluate a new PlaneView software load as well as the B&CA demonstration. We strapped into the left seat, with Howard in the right and safety pilot Bud Ball at the observer station. The improvement in cockpit legroom was the first thing we noticed. In the back, flight-test engineer Peter Handy operated equipment at the flight-test station.

Compared with GIV/400-series airplanes, GV/550-series aircraft have much simpler systems operation. The G550 overhead panel in the G450, for instance, has considerably fewer switches, better automation, reduced checklist item count and lower pilot workload. Bleed air automatically is shut off to the ECS during main engine start, and the main engine-driven electrical generators automatically come on line with no need for pilot intervention. The flow checks in the G450, as a result, go much faster than those in the GIV/400.

With minimal insulation and flight test equipment, s.n. 4004 had an empty weight of 39,705 lb. Adding in four crewmembers, the zero fuel weight was 40,385 lb. The lack of a completed interior pushed the c.g. at ZFW fairly far forward in the envelope. Loaded with 15,000 lb. of fuel, the actual ramp weight was 55,385 lb. and the computed takeoff weight was a svelte 54,885 lb., resulting in a sporty 1.98:1 weight-to-thrust ratio. Takeoff speeds were 118 KIAS for V1, 124 KIAS for rotation and 132 KIAS for the V2 one-engine-inoperative takeoff safety speed. The outside air temperature was 24C (ISA+9C) and the takeoff field length was 3,840 ft. The G450 has basically the same ground handling characteristics as the GIV/400, but Gulfstream still is fine-tuning the ABSC wheel brake response so that it's as smooth and refined as the G400's Dunlop system. The carbon/carbon brakes also were a little grabby when cold, typical of many such high performance brake packs on business jets.

Lined up for takeoff on Runway 09, Howard pointed out that there's no longer a need to push up the thrust levers to 1.15 EPR prior to engaging the auto-throttle system, rather only a slight increase in throttle movement is required prior to engaging the system for the FADEC-controlled Tays. We smiled at rotation, noting that the G450's pitch forces are noticeably lighter than those of the G400.

After gear retraction and passing through 400 ft. AGL while accelerating through 160 KIAS, we retracted the flaps. A large reduction in thrust was required to prevent busting the 200 KIAS Class D speed limit. Later we climbed to 11,000 ft., en route to the warning areas over the adjacent North Atlantic. We noted that the decreased roll control forces make the G450 a pleasure to hand-fly. It's every bit as nice as the G550, which has the nicest handling qualities since the GII, in B&CA's opinion.

“Sea Lord,'' the military ATC agency that owns the warning areas, cleared us into an airspace block from sea level to 51,000 ft. That enabled us to descend to 1,000 ft. MSL and slow to 152 KIAS to begin a time-to-climb check. “Go,'' Howard said, and we accelerated to 250 KIAS in IAS+8C conditions. We held 250 KIAS until reaching 10,000 ft. and then accelerated to the recommended 300 KIAS/0.80 IMN climb speed. Outside air temperatures were as much as 10 above standard during the climb through 41,000. Then, the air cooled to ISA-5C to ISA-6C for the final ascent to FL 450. Total climb time was 20 minutes and fuel burn was 2,000 lb., as we leveled at a weight of 51,850 pounds.

Notably, a fully loaded G450 will be able to reach FL 410 in 22 minutes, three minutes sooner than a G400. The difference in climb time to FL 450 would be larger, especially in warm day conditions. Using maximum cruise thrust, the aircraft stabilized at 0.84 Mach, equivalent to 474 KTAS at ISA-5C while consuming 2,830 pph. Then we slowed to 0.80 Mach to check long-range fuel flows. High-altitude turbulence and mild up and down drafts prevented us from stabilizing “on condition,” but it appeared that fuel flows were about 2,250 pph, resulting in an average specific range of 0.200 nm/lb. at an average weight of 51,000 lb.

We then descended to FL 370 for an APU start and run check at 173 KIAS. Howard reached up and pressed the button. The 36-150GIV performed flawlessly, assuming half of the electrical load when we turned off the left engine-driven generator. At 15,000 ft., we performed a few steep turns. The softer control forces, combined with the precision guidance of the flight path vector on the Honeywell Visual Guidance System (HUD), made these maneuvers much easier than in the old GIV. We declined to perform any approaches to stalls because the stall barrier protection system was inoperative during the flight.

Returning to SAV, we entered the VFR landing pattern downwind for Runway 09, flying two touch-and-goes, followed by a full stop. Then, we departed Runway 09 and Howard pulled back the thrust lever on the right engine after V1, simulating an engine failure. The associated control forces were considerably softer than those of the GIV/400, making the aircraft much easier to handle during the maneuver. With 13,850 lb. of thrust on tap, though, the aircraft seemed to climb better with one engine inoperative (simulated) than some business aircraft perform with all engines in operation.

We flew downwind in preparation for returning to land, still with the right engine at idle, when a light aircraft declared an emergency. This provided us with more time to fly the aircraft using only the left engine and circle to land on Runway 27. Responding to this unforeseen event in the G450 was no problem. We lined up with Runway 27 and landed with a full-flaps approach speed of 128 KIAS. Using only the left thrust reverser, we slowed to taxi speed using minimal wheel braking. Total fuel burn for the 2.4-hr. demo flight was 8,400 lb.

Price, Value and the Competition

B&CA's Comparison Profile provides an indication of how well the G450 stacks up against its prime competition, the Bombardier Challenger 604, Bombardier Global 5000, Dassault Falcon 900C, Dassault Falcon 900EX and Gulfstream G400 (the aircraft the G450 is replacing). This is one of the closest comparisons B&CA has seen in recent years, with most relative scores of the G450 falling within 10% to 15% of the average. The G450's obvious strong points are cabin length, payload capacity and climb performance. It has the best thrust-to-weight ratio in its class and it easily out-climbs the competition to higher initial cruise altitudes. It has a long-range cruise speed of 0.80 Mach, equivalent to 459 KTAS on a standard day, which is considerably faster than most other large cabin competitors, except for Bombardier's Global 5000. Some models cruise at 0.75 Mach and slower. This gives the G450 more of a range advantage when bucking strong headwinds, typical of westbound transatlantic missions in the winter. As one might expect, the downside is somewhat higher fuel consumption, also which is reflected in the Comparison Profile.

But our Comparison Profile doesn't measure other relevant parameters, such as dispatch reliability, overall cost of operation and advanced avionics capabilities. In these areas, the G450 likely will score well above many competitors, based upon operational statistics compiled for GIV/400- and GV/550-series aircraft and the capabilities provided by the G450's PlaneView cockpit with standard VGS and EVS. Gulfstream also has earned a reputation among operators for providing the best product support among large cabin business aircraft manufacturers. The G450, though, won't spend as much time in the shop as GIV-series aircraft because it has extended scheduled maintenance intervals and its Rolls-Royce Tay 611-8C turbofans have the longest HSI and TBO intervals in class.

For folks in the market for large-cabin business aircraft, the G450 is more than the next-generation GIV. It's actually the newest, smallest and lowest-priced member of the GV family, albeit one that's virtually wrapped in G400 aluminum. As so, it's a worthy successor. Its enhanced performance, updated systems, PlaneView avionics, reduced operating costs and probably high dispatch reliability are almost sure to earn it a loyal following among Gulfstream IV/400 operators, and others needing a long-range, large-cabin business aircraft.

Gulfstream G450 Preliminary Specifications

B&CA Equipped Price (2003) $33,000,000


Seating 2+14/19

Wing Loading 77.8

Power Loading 2.67

Dimensions (ft/m)


Length 8.3/2.5

Height 25.2/7.7

Wingspan 77.8/23.7


Length (OA) 45.1/13.7

Length (Net) 37.0/11.3

Height 6.2/1.9

Width (Maximum) 7.3/2.2

Width (Floor) 5.5/1.7


Engines 2 Rolls-Royce Tay 611-8C

Output (lb. ea.) 13,850

Flat Rating OATC ISA+15C

TBO (hr.) 12,000

Weights (lb./kg)

Max Ramp 74,300/33,702

Max Takeoff 73,900/33,520

Max Landing 66,000/29,937

Zero Fuel 49,000c/22,226c

BOW 43,400/19,686

Max Payload 5,600/2,540

Useful Load 30,900/14,016

Executive Payload 2,800/1,270

Max Fuel 29,281/13,282

Payload With Max Fuel 1,200/544

Fuel With Max Payload 25,300/11,476

Fuel With Executive

Payload 28,100/12,746


MMO 0.880

FL/VMO FL 280/340

PSI 9.7


Time to Climb/

Altitude 16 min./FL 370

FAR Part 25 OEI Rate (fpm) NA

FAR Part 25 OEI Gradient (ft./nm) NA

Ceilings (ft./m)

Certificated 45,000/13,716

All-Engine Service 42,000/12,802

Engine-Out Service 24,000/7,315

Sea Level Cabin 26,100/7,955

Certification FAR Part 25, Amend. 92

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