The wait is over. On October 14, Gulfstream rolled out the G500, the first of two models from its secretive P42 development program. In the works since 2008, the project actually spawned two new models, the 5,000-nm G500 and the 6,200-nm G600. Both look a lot like the firm’s 7,000-nm G650 flagship, but they have less range, smaller cabin cross-sections and lower price tags. The G500 is priced at $43.5 million and the longer G600 will go for $54.5 million.

The new models aren’t mere design dreams. Both are well along in their development cycles with 1,800 hr. of wind-tunnel work complete. Critical design review of the G500 was completed in fourth quarter 2012, while the G600’s design freeze is slated for the end of this year.

Assembly of the wings, tail and fuselage of the first G500 flight-test aircraft is nearly complete with first flight planned for 2015. G500 certification is scheduled for 2017 and entry into service in 2018. A year later G600 deliveries are to begin.

The G500’s shape speaks reams about its speed, as well as it spaciousness compared to the G450. And while it’s not much longer than the GIV derivative, it has 10 ft. more wing span and a considerably bigger cabin. It will fly higher, faster, quieter and farther on less fuel. For instance, it will have 18% more range at its long-range cruise speed of Mach 0.85 while burning less fuel than the G450’s range of 4,220 nm at Mach 0.80.

At Mach 0.90, two ticks above the G450’s Mach 0.88 redline, the G500 will be able to fly 3,800 nm. The enhanced performance mainly is due to G650 wing aerodynamics, including a super-critical airfoil with 36 deg. of sweep at quarter chord and the new Pratt & Whitney Canada PW800-series engines.

Meanwhile, the G600 will be able to fly 200 nm farther at Mach 0.85 on less fuel than the G550’s 6,000-nm range at the same cruise speed. It also will able to dash 4,800 nm at Mach 0.90. The G550, though, retains a 550-nm range advantage at its long-range cruise speed of Mach 0.80.

“We have a very-long-term development strategy. Cabin volume, range and speed were the design drivers,” said Scott Neal, Gulfstream’s senior vice president worldwide sales and marketing. “[That combination] will be matched by no other aircraft.”

This marks the first time that a purely U.S.-designed Gulfstream will powered by engines not made by Rolls-Royce. Gulfstream officials were careful when commenting on engine choice, saying only that the Pratts offered the best blend of maturity, weight, performance, fuel efficiency and operating economy for the new aircraft. They added that Rolls-Royce engines continue to perform well aboard the G450, G550 and G650, among other models.

The G500 will be fitted with two 15,144-lb.-thrust PW–814GA turbofans, Honeywell avionics and fly-by-wire (FBW) flight control systems furnished by BAE Systems, Moog, Parker and Thales. Five aircraft, along with static and fatigue ground-test articles, will be used for the two-year, 3,000-hr. flight test campaign.

The G600 enters flight test in 2016. Its longer fuselage will accommodate two more cabin windows, while its wider span wings hold more fuel and the PW815GA engines will deliver 15,680 lb. thrust.

Part G650, Part Clean Screen

G450 and G550 operators told Gulfstream they wanted an aircraft with a bigger fuselage cross-section and better fuel efficiency. The manufacturer briefly evaluated using the G650 fuselage cross-section for the G500 and G600, but the associated weight and drag imposed unacceptable performance penalties. That’s what necessitated developing a new fuselage with a somewhat smaller cross-section. Similar to the G650, it’s a semi-monocoque aluminum structure that uses extensive adhesive bonding of longerons and skins. This reduces the number of mechanical fasteners, thereby shrinking assembly hours and producing smoother skin contours.

Also similar to the G650, the new aircraft will a four radii cross-section fuselage shape that provides more head and shoulder room in the cabin than does a circular cross-section. The fuselage is 7-in. narrower in width and shorter in height than that of the G650. The cabin floor sits proportionately relatively lower in the fuselage than in the G650, so the G500 and G600 have only 1 in. less headroom than the flagship.

Compared to the G450 and G550, however, the G500 and G600 will have 2 in. more headroom, 7 in. more cabin width and 8 in. more floor width. The club section and conference group chairs are wider than those aboard the G450 and G550 and the center aisles are 2 in. wider. The interior cross-section dimensions are similar to current production Dassault Falcon jets.

The new aircraft will use the same cabin windows as the G650. They are 16% larger in area and positioned 3.4-in. higher on the fuselage than the transparencies of the G450 and G550. The longitudinal spacing between window centerlines is 52.5 in., the same as on the G650. That’s 3.5 in. more distance between windows than on the G450 and G550.

Each seating area has two windows on each side and is 105 in. long. That translates into 7 in. more legroom between facing chairs. And side-facing divans gain 7 in. of length, a welcome improvement when they’re used as berths. The G500’s cabin is 2.6-ft. longer than that of the G450; the G600’s cabin will be 1.2-ft. longer than the G550’s.

The G500 has six windows on each side and three seating areas with flexible seating arrangements. The G600 has seven windows on each side, making room for 3.5 seating areas. The G600’s extra length accommodates an optional FAR Part 135-compliant crew rest compartment. Usable cabin space in both aircraft is increased because the aircraft have much slimmer left and right electrical equipment racks between the cabin and cockpit.

The aircraft will have a 10.7-psi pressurization system that provides a 4,850-ft. cabin altitude at FL 510 and a 3,000-ft. cabin altitude at FL 410. The new Gulfstreams will have the lowest cabin altitudes in their classes.

The 175-cu.-ft. aft baggage compartment should have full-time inflight access. It’s been redesigned with new shelving and several additional cargo net anchor points to improve space utilization.

Front and rear galley configurations are available. Both aircraft have forward and aft vacuum lavatories. Storage capacity inside the cabins is increased because of improved space utilization in the galleys and lavatories. Many of the 200 design changes made to the aircraft during the last six years were suggested by the cabin attendants who participated in Gulfstream’s advanced technical customer advisory team (ATCAT).

Similar to the G650, composites will be used for secondary structures, such as the aft pressure bulkhead, horizontal stabilizer, radome, fairings, nacelles, gear doors, spoilers and primary control surfaces. Aluminum will be used for the flaps.

Several systems are carried over from the G650. The electric system, for instance, will have left and right engine-driven 40-kVA generators, a 40-kVA APU-driven generator and a 15-kVA ram air turbine. The dual 3,000-psi hydraulic system, filled with phosphate ester fluid, will be powered by high capacity, left and right engine-driven pumps, plus a left-side electrically powered aux pump and a left-to-right power transfer system. There will be no need for a hydraulically powered motor generator.

Also shared with the G650 are the digital air data computers, secondary power distribution with electronics, cabin acoustical treatment, primary avionics, satcom and cabin management system (with improvements). The digital FBW system is similar to that in the G650, having a pair of dual-channel Thales flight control computers and Parker electronic power control actuators. The two notable exceptions are the new active sidestick controls furnished by BAE Systems and dual-channel remote electronic units that replace single-channel units on board the G650.

The oxygen, cabin pressurization, landing gear control, and aircraft health and trend monitoring systems are adapted from the G650, but they’re more fully integrated with the avionics system.

About the only things these aircraft have in common with the G450 and G550 are the number of cabin windows; the G500 has 12 and the G600 has 14.

More Upfront Preparation

General Dynamics, Gulfstream’s parent, is investing heavily in new facilities, mostly sited at the northwest corner of the Savannah/Hilton Head International Airport. The company is moving toward more vertically integrated manufacturing with the goals of improving quality and reducing build costs. The wings of the new aircraft, for instance, will be built in-house, a first for Gulfstream. This required investment in CNC mills and other automated manufacturing processes, along with an autoclave used for age creep forming of wing skins.

More preflight development work is being done for the two new aircraft than for any previous Gulfstream models. The object is to streamline the flight test program by doing the design and development work on the ground and then flying the aircraft mainly to verify and validate the results. The goal is to eliminate early serial number syndrome, to deliver mission-ready aircraft upon initial entry into service.

Operational testing includes use of an interactive 3-D theater that allows engineers to “walk through” a digital model projected on a screen to check form, fit and functionality. Gulfstream calls this its “conceptual advanced simulation environment” (CAVE) and it’s similar to the systems already in use by Airbus, Boeing, Dassault and Embraer.

Similar to the G650, Gulfstream built both an integrated test facility and an iron bird test rig to evaluate the functionality of most airframe systems, including electrical, hydraulic, power control actuator and environmental system components.

Its advanced acoustical lab, staffed in part by engineers transferred to the Georgia facility from General Dynamics Electric Boat submarine plant in Connecticut, reduced the G650’s interior sound levels by several decibels. The same team now is working on making the G500 and G600 as quiet as the G650, an aircraft that Gulfstream claims is the quietest business jet yet.

The firm also has an integrated cockpit and cabin mockup that has the actual equipment that will be used aboard production aircraft, along with the latest versions Gulfstream’s cabin management system (CMS). The goal is to wring out bugs before the first production aircraft, including potential problems with coffee pots, microwave ovens, water and waste systems, and refrigerators. Early G650 operators complained about the poor reliability of Gulfstream’s CMS and the manufacturer wants the system aboard the G500 and G600 to be considerably more reliable.

When the G650 entered service, Gulfstream learned that its non-circular fuselage flexes differently under pressurization loads than a circular cross-section fuselage. The flexing caused gaps in some interior sidewall seams and warping of some panels. Gulfstream engineers say they’ve learned from the experience and made changes to interior mounts. The cabin furnishings of the G500 and G600 should fit much better under similar loads.

The G500 and G600 should find strong acceptance among G450 and G550 operators looking to upgrade their aircraft. They offer substantial improvements in cabin size, performance and fuel efficiency. This blend also has potential for attracting new customers outside the Gulfstream community, particularly as they will offer the lowest cabin altitude and, arguably, the latest technologies of any business aircraft yet announced.

The G500 will compete directly with the Dassault Falcon 900LX and upcoming Falcon 5X in cabin size, range and price. The Falcons will remain class champions for fuel efficiency, but the G500 will cruise higher and faster.

Similarly, the G600 will vie against the new Falcon 8X. The Dassault offering has a slightly longer cabin and better fuel efficiency, but the G600 will fly faster, farther and higher.

The new Gulfstreams also compare favorably with Bombardier’s existing Global 5000 and 6000 models, even though those aircraft have slightly large cabin cross-sections. The G500 cedes up to 400 nm of range to the Global 5000, but it cruises faster, offers far better fuel efficiency and its price is $6.6 million lower. The G600 has a 3-ft. shorter cabin than the Global 6000, but it cruises faster and farther on less fuel. The Gulfstream also is priced $7.5 million lower.

Industry sources long have speculated that the Georgia firm was developing replacements for the G450 and G550. Neal, though, claims that the new aircraft are not replacements but additional models meant to help fill gaps between the G450/G550 and the firm’s G650 flagship. Gulfstream officials say the G450 and G550 “are selling well.”

But the market appeal of the G450, and perhaps the G550, could sag as prospective customers learn more about the capabilities of the new models. Two or three decades ago, business aircraft travelers expected to fly at Mach 0.80, with an occasional dash as fast as Mach 0.85.

Gulfstream is recalibrating customer expectations with the G500, G600 and G650. These aircraft not only have considerably larger cabins than previous Gulfstream aircraft, they also set new standards for speed. Operators can now expect to slow down to Mach 0.85 only when necessary to achieve max range. Gulfstream boasts that Mach 0.90 is the new “normal cruise” for business aircraft travel. Compared to poking along at Mach 0.80, that cruise speed can slash an hour, or more, off the flight time between continents.

BAE ‘Active Inceptor’ Sidesticks

Gulfstream’s G500 and G600 will be the first civil aircraft to be fitted with “active inceptor” sidestick controls — that is controls that are electrically back driven so that they appear to be mechanically linked side to side. Thus, when one sidestick is moved, the opposite sidestick moves with it. The sidesticks also move in response to autopilot inputs, providing the pilots with tactile and visual feedback.

Similar to the G650, the primary high-level pitch control law for up-and-away operations will be Nz, or vertical acceleration, command, with “U” speed stability. The pilot will need to trim pitch for speed changes. The sidesticks will have four-way switches on top, providing pitch and roll trim functions.

As an added bonus to flight crews, the transition from control wheels to sidesticks allows the cockpit seats to be fitted with full-length and -width bottom cushions without center cutouts to make room for the yokes.

Gulfstream Symmetry Flight Deck

Symmetry is Gulfstream’s name for its new-generation G500 and G600 flight decks. These will feature business aviation’s first “active inceptor” sidesticks, along with touchscreen controls and other innovative features that will distinguish the cockpits from the PlaneView flight decks of current-production Gulfstream jets.

There are 10 Symmetry touchscreen controls in the cockpit and galley. On the flight deck, three large, software-driven touchscreens on the overhead panel will control virtually all airframe systems. Four smaller touchscreens, two outside the main display screens and two in the center console, will provide FMS, radio and avionics/display controls. The transition to touchscreen controls from hard buttons, knobs and switches provides unprecedented redundancy. Gulfstream’s goal is to allow dispatch with one overhead touchscreen control, one lower touchscreen control and one standby flight display inoperative.

The aircraft will not have conventional multifunction CDUs. Wider screen standby flight instruments are installed in the glareshield.

The cursor control devices will be relocated from the sidewall armrests to the center console to make room for the sidestick controls.

The new aircraft also will be equipped with standard HUDs and third-generation Elbit Kollsman EVS III IR cameras having four times the image resolution, an integrated exterior window panel and a digital interface to the avionics suite.

Pratt & Whitney Canada PW800 Engines

The PurePower PW814GA and PW815GA engines have higher thrust, lighter weight and are more fuel efficient than current-generation 16,000-lb.-thrust-class turbofans that power large-cabin business aircraft. They share their eight axial stage compressors, TALON X low-emissions combustors and two-stage high-pressure turbines with Pratt & Whitney’s geared turbofan engines designed for commercial jetliners.

These are conventional two-spool engines. In place of the geared fans up front, the engines will have 20-blade, single-piece, direct-drive titanium fans about 50 in. in diameter and three-stage low-pressure compressors or superchargers driven by three-stage low-pressure turbines. Bypass ratio is approximately 5.5:1. The exhaust section will have tabbed, deep-fluted mixer nozzles.

Pratt & Whitney Canada officials say that emissions and noise levels will have “double digit” margins to ICAO’s proposed CAEP/8 and existing Stage IV standards, respectively.

Working with Nordam, P&WC is developing an advanced nacelle system that improves engine intake and exhaust flow efficiency, particularly when the thrust reverser is stowed.

A prime design goal is 40% lower scheduled maintenance cost and 20% fewer maintenance inspections. The nacelles are designed for easy access to engine components. Most accessories can be removed and replaced in 30 min. or less. There are multiple borescope access ports for internal inspections. Initial TBO is 10,000 hr. and there are no midlife inspections. B&CA