Story ID: 040G500G600AINAug16EditedByAY_NM
Gulfstream G500, G600 Programs Accelerating
By: Matt Thurber
Caption: Gulfstream’s new fly-by-wire jets take advantage of the latest technology to make flying safer and simpler.
Word Count: 2087
In two new buildings at Savannah Hilton Head International Airport, Gulfstream’s assembly lines for its newest jets, the G500 and G600, are already packed with action. Four G500s are in flight-test, and the first flight-test G600 will be handed over soon in preparation for first flight early next year or possibly sooner.

At one end of Building Z, a giant machine drills and rivets fuselage panels, stitching frames onto carefully curved pieces of aluminum that have already been fitted with chemically bonded stiffening stringers. The machine barely makes any noise as rivet heads are squeezed with accurately applied force onto an oppositely held tool that squishes the shank into perfectly formed FAA-standard shop heads with a regularity and consistency that is impossible for even the most artful human riveting team to accomplish. Another tool follows behind, shaving slivers off the tiny portions of the recessed flush rivets that still peek slightly above the skin they are securing.

Thus jigged, bonded, drilled, riveted and shaved, much of which is done by untiring machinery, the panels move along and find themselves attached to precision build carts, their home until they take the final shape of what will become the fuselage of a new jet. Each cart holds a barrel section of the fuselage—nose, center barrels, tailcone—and each barrel except for the nose itself and the final cone of the tail forms a strengthened circular edge that fits one inside another. When each barrel is ready, the precisely positioned carts are moved together, the barrels join and eventually the entire fuselage sits on a train of precision carts while assembly techs plug hundreds of holes with rivets and—there is no machine for this—permanently mate the barrels together with rivet guns and bucking bars, which solidify the newly formed fuselage with the same good old-fashioned clatter that got aviation this far.

Next door in Building Y, Gulfstream’s first in-house wing factory, similar work takes place with painstaking accuracy, machinery as technicians measure, drill, rivet, bolt, install, test and measure again and again before finished wings roll briefly into the open then back inside to mate with a fuselage suspended in the air by massive straps hooked to overhead cranes. The long wing, each tip not diverging by even tiny fractions of an inch from its twin lest the airplane not fly straight, waits patiently as the fuselage eases down, down, further, just a little more, and success, the critical holes line up, bolts that are more than strong enough but look so small compared to the massive structure are gently nudged into a home they likely will never leave.

 All this work in Buildings Y and Z is the culmination of years of effort and represents the application of the latest manufacturing technology as well as the most modern expression of cockpit and cabin design features in any Gulfstream jet. For one example, the active control sidesticks (ACS) that are a distinct feature in the G500 and G600 were considered for the G650 program; all three aircraft are equipped with fly-by-wire flight control systems, but when the G650 was being designed, the ACS technology wasn’t quite ready. Now the ACS have completely opened up the G500 cockpit, which is identical to the G600’s, giving engineers much more latitude on layout and comfort.
 Symmetry Features
The new features don’t stop with the flight controls and, working with avionics supplier Honeywell, Gulfstream has rethought the pilot-airplane interface and vastly simplified the way pilots tell the avionics and automation what to do. While the G650’s avionics are basically an updated iteration of the G550’s, the G500/G600 Symmetry flight deck and the electronic architecture that supports it are substantially new.

Yet at the same time, G450, G550 or G650 pilots will find many familiar interface conventions in the new jets, so transitioning should be smooth. This extends to the flight controls as well, because the G650’s fly-by-wire controls preserve the feel of flying a conventional Gulfstream, and the G500 and G600 use the same fly-by-wire system architecture, but with sidesticks instead of bulky yokes.

From startup to shutdown, the Symmetry flight deck has been simplified and improved, taking advantage of new technology without making the pilot-machine interface more complex. While an experienced flight crew spends about 17.5 minutes taking a legacy Gulfstream from dark cockpit to ready to taxi, in the G500 it takes just over 10 minutes, according to engineering test pilot Scott Evans.

Gone are the switchlight-festooned overhead panel and multiple switchlights scattered throughout the cockpit in seemingly random places. The FMS MCDUs, for many years occupying a prominent place in the center pedestal, no longer exist, at least not in their familiar form. The same is true of many other cockpit features: for example, the audio control panels are also gone. Yet all of these controls remain etched electronically in system software and still accessible to the pilot, primarily through touchscreen controls.

Gulfstream always wants the pilot in the loop, and unnecessary subtasks are now eliminated but still accessible. When starting the APU in a G550, the crew needs to run the APU fire test, turn on the left main boost pump and external lights, turn on the APU master switch then start the APU, and once that is running switch on the IRSes. In the G500, the fire test still needs to be done, but once the APU master is on (task initiated), the rest (subtasks) is done automatically, including boost pump and lights on, followed by the IRSes on after APU start. The same happens with engine start: there is no longer a start master switch, and the crew just needs to move the run switch to the run position, then the G500 turns on the main boost pump and configures the bleed air, then the crew pushes the start switch, and that’s it. All of the subtasks are still accessible manually, but the idea is to put the system into the desired state when needed with a minimum number of steps.

The new avionics philosophy is designed to help the pilot manage the airplane by phase of flight, providing information when it is needed. Pilots can use the touchscreens to access familiar functions, such as the FMS, display controller and so on, but even those are made simpler, with no need to press FMS line select keys to access page after page of information. Now the pilot swipes the touchscreen controller to access various functions. Left to right pulls up the phase-of-flight menu structure, with tabs for each phase. Just select a tab, fill in the necessary information, and that’s it. If the airplane isn’t configured properly, it will tell the crew, for example, via amber V speeds. The system graphically depicts how much runway is needed, instantly helping the crew determine that a takeoff is runway-critical.

The BAE Systems ACS (sidesticks) are yet another pilot-in-the-loop feature, because not only are they synchronized to move together so pilots can visually observe the movement—just like yokes—but the flight control system is tuned to replicate the handling of a typical Gulfstream. Unlike the fly-by-wire system in other business jets, which are designed with neutral speed stability and stabilize in whatever flight path the pilot selects, the G500/G600 system employs positive speed stability, which results in handling more like that of a traditional airplane, Evans explained. If, say, a G550 is trimmed to fly at a particular speed, displacing it from that speed means the pilot will feel a force on the controls, and that force can be trimmed off, helping keep the pilot in the loop with sensory feedback, he added.

One difference on the fly-by-wire Gulfstreams is an autospeed trim function, under which the pilot can quickly set pitch trim to the existing airspeed by pushing the autopilot disconnect switch. This is much faster than retrimming with the hat switch on the yoke, but it still serves to keep the pilot in the loop.

“It is such a fun airplane to fly,” Evans said, “but more important it is designed with the pilot in mind, to make our job easier and let us focus more on the busy environment in the outside world.”
 Certification Progress
The G500 is steadily moving toward FAA certification next year, and much of the work done on this jet will help move the longer G600 through certification and entry into service more smoothly. The G500 is set to enter service in 2018, followed by the G600 in 2019. Four G500s are now in flight-test, and the first G600 will soon be handed over to the flight-test team. Although the G600’s first flight is officially scheduled for early next year, it could fly late this year.

As of mid-June, the G500 fleet had logged more than 280 flights and 1,100 hours. Milestones include reaching a Mach 0.995 (maximum operating speed is Mach 0.925), 53,000 feet (2,000 feet higher than the planned certified ceiling) and the longest flight at seven hours, 35 minutes, with zero discrepancies, according to Gulfstream.

The G500 and G600 are an entirely new line of jets, and what sets them apart from the G450/G550 line is their larger cabins, which measure 7 ft 11 in wide and 6 ft 4 in tall. While this is smaller than the 8 ft 6 in width of the G650, the G500/G600 cabin is a step up from the G450/G550’s 7 ft 4 in width and 6 ft 2 in height. Cabin volume of the new jets is also larger, with the G500 at 1,715 cu ft (48.6 cu m) and the G600 at 1,884 cu ft (53.3 cu m), compared with 1,669 cu ft in the G550.

The G500/G600 also maintain the generous seat pitch and spacing between seating groups and the same large windows of the G650. While the first G500s were fitted with six windows on each side—the G600 has seven—Gulfstream designers were able to add a seventh window to the G500’s cabin, so it will be a hard to tell the two models apart by just looking at the window count. The seventh window will cut into the production line with G500 Serial Number 7, which is the first customer airplane. Many of the interior features are a direct result of input from members of Gulfstream’s advanced technology customer advisory team. The team’s efforts yielded 200 design changes, among them the large windows, seat cushion comfort and cabin management switch feel.

Up to 19 passengers can be accommodated in the G500 or G600, and each aircraft offers the option of a forward or aft galley. Like the G650, the new jets pressurize the cabin to 4,850 feet at the 51,000-foot maximum altitude passenger comfort and fatigue reduction (which also benefits the crew). Gulfstream’s own cabin management system provides in-flight entertainment and operation of cabin comfort and lighting systems.

The G600’s cabin is nearly four feet longer than the G500’s, and the two jets also differ in range. The G600 can fly 6,200 nm at Mach 0.85 carrying eight passengers and four crew with NBAA IFR reserves. The G500’s range under the same conditions is 5,000 nm, although with one fewer crewmember. Both offer high-speed cruise of Mach 0.90. Engines on the G600 are Pratt & Whitney Canada PW815GAs each rated at 15,680 pounds of thrust. The G500’s PW814GAs develop 15,144 pounds of thrust.

Gulfstream engineers recently passed a significant milestone for both aircraft, the 150-percent ultimate load test, in which an airframe is subjected to stresses significantly greater than the airplane is ever likely to encounter. Meanwhile a static ground-test airframe is being subjected to fatigue testing that will eventually replicate three airframe lifetimes. 

Gulfstream pilots have already been “flying” the new jets in laboratory simulators and fine-tuning the pilot-machine interface, but a more realistic simulator is also now in place at the FlightSafety learning center next to Gulfstream’s headquarters in Savannah, Ga. The FlightSafety simulator will be certified in time for pilot training ahead of entry into service, but in the meantime it is being used for human factors and development of flight crew procedures and other work.

Gulfstream hasn’t published any backlog numbers for the G500/G600 yet, but there are two launch customers, Qatar Executive Airways and Flexjet