Pilot Report: Gulfstream G500
The recently certified G500 represents a leap forward in flight-deck and flight-control-interface design—a bold move for a manufacturer as conservative as Gulfstream— yet also a logical progression in business jet design. The G500 is a delight to fly and a significant step up in handling compared with the non-fly-by-wire (FBW) designs (G550 and below). The many touchscreens that run the avionics and other systems feel as natural as wings on airplanes.
Although the G450 is out of production, the G550 remains in demand and will continue rolling off the production line as long as buyers continue placing orders for the 6,750-nautical-mile ultra-long-range jet. If that much range (or the range of the G650) isn’t needed but a wider cabin and higher speed is, then the G500 and G600 ought to be a logical choice for those who appreciate the Gulfstream brand.
The new cabin measures 91 inches wide and 74 inches high, while the G550 is 84 and 72 inches and the G650 is 98 and 75 inches. Range at Mach 0.90 with eight passengers and three crew is 4,400 nautical miles in the G500 and 5,100 nautical miles in the G600. Throttle back to Mach 0.85 and range climbs to 5,200 and 6,500, respectively. Those numbers, incidentally, are higher than originally projected: the G500’s range grew by 600 nautical miles at Mach 0.90 and 200 nautical miles at Mach 0.85. The G600’s range climbed 300 nautical miles at both speeds.
The new jets carry the Gulfstream heritage forward, retaining the T-tail and clean-wing layout, but also incorporating the trailing-link landing gear of the G650. The G500/G600 wing is Gulfstream’s first wing assembly manufactured in-house, and the new models represent a significant step up in Gulfstream’s vertical integration, as well as being clean-sheet designs with their own type certification.
The two models are produced in the same building at Gulfstream’s Savannah, Georgia headquarters, with wings and horizontal stabilizers manufactured in an adjacent facility, then moved over for mating with the fuselage.
“We’re using a significant amount of technology in the manufacturing process,” said Mark Kohler, vice president, Advanced Aircraft Programs. A phalanx of automated machinery drills, countersinks, deburrs, then installs and squeezes rivets to attach stringers to formed wing panels. Then ribs, spars, and skins are located and installed in a wing-assembly fixture.
The horizontal stabilizer is classic Gulfstream, larger than is needed to counterbalance wing lift because this way the stabilizer doesn’t need supplemental icing protection, simplifying systems design and manufacturing complexity.
Symmetry Flight Deck
While the cabin features the latest in Gulfstream interior design and manufacturing, what sets the G500/G600 apart from other Gulfstreams, even the G650, is the Symmetry flight deck. There is much more to it than just replacing the G650’s yoke controls and traditional avionics with active-control sidesticks (ACS) and touchscreens, and engineers spent an enormous amount of time on human factors design and testing. The sidesticks (also known as active inceptor systems) are electronically interconnected and move in concert, and they are designed by BAE Systems and also the first commercial application of ACS. Other aircraft that incorporate the BAE ACS are military designs such as the F-35 Lightning II, UH-60Mu Black Hawk, T-50 Golden Eagle, and CH-53K Super Stallion.
From a systems perspective, the big change with Symmetry is a newly added data-concentrator network (DCN), which forms the backbone of the new jets’ electronic network. The DCN connects all systems, and any data from those systems can easily be shared, published on synoptics displays, and used for systems controls and to support health and trend monitoring. More than 15,000 parameters are monitored, and data is distributed via 14 routers installed throughout the airframe, connected via Ethernet cable. If there is a failure anywhere in the DCN, the data is still available because it is published to multiple routers. Adding new features to the G500 and G600 will be far simpler, because they can be plugged into the DCN instead of adding new wiring. The big advantage of the DCN is that it eliminates 200 to 300 pounds of components and wiring and makes new space available for cabin furnishings.
The most dramatic change in the flight deck is the proliferation of touchscreen controls. There are 11 touchscreens, although the number most often mentioned is 10 because one of them, the security system interface, is not something the pilots would usually use during flight.
It’s normal for pilots, especially those who haven’t flown any aircraft with touchscreens, to question their utility, especially in turbulence. But there are other considerations that make touchscreens so sensible in modern aircraft, and in any case, flying through turbulence doesn’t take up a large percentage of flying time.
Scott Evans, now Gulfstream director of demonstration and corporate flight operations, and previously a project pilot on the G500/G600 program, spent hours testing touchscreens while driving in a van on bumpy roads and airborne in turbulence to make sure the controllers were ergonomically as good as they could be in a variety of conditions. Bevels or plinths around each of the touchscreens allow the pilot to maintain a firm grip while actuating the touch features.
The Gulfstream touchscreens are resistive, which requires more finger pressure (at least 100 grams or three ounces) than typical consumer tablets or phones that have capacitive touchscreens, and this helps avoid inadvertent moves. Actuation of the selected element occurs when the pilot lifts a finger off the screen. Other gestures are available too, including swipes for quick access to various pages, pinch-to-zoom, etc.
It should be noted that the Honeywell Epic-based displays in the G500’s Symmetry flight deck will be abundantly familiar to Gulfstream pilots. They are not touchscreens, although Honeywell has designed fully touchscreen Epic displays that have yet to be selected by an OEM. For a pilot familiar with the G450/G550, the cursor control device-based user interface remains exactly the same. The difference with the G500 is that the CCDs live in the center pedestal instead of on the outboard ledge, a vast improvement in my opinion as the CCD’s stalks in the G450/G550 take up a lot of valuable space.
There are four touchscreen controllers in the forward flight deck, one each outboard, and in the pedestal, two that replace the FMS multifunction control and display units (MCDUs). The jumpseater has a dedicated touchscreen controller, which is also available for maintenance technicians. The banks of mechanical circuit breakers are almost gone now, with 45 percent replaced by electronic circuit breakers.
The overhead panel is wonderfully clean, with three identical Esterline Korry touchscreens replacing what seems like the gazillion overhead switchlights, knobs, and buttons on the G450/G550.
With just one switch on the center pedestal—the flight control reset switch—engineers were able to make it skinnier and add two cupholders on the rear. As Airbus pilots have been able to do for many years, G500/G600 pilots can pull out a retractable desk/meal table mounted on the bottom of the instrument panel, thanks to the space-saving sidesticks.
Mimicking a design change on the G650, the multifunction controllers on the G550 are gone, with all those functions available via the touchscreen controllers or using two L3 Aviation standby instruments mounted under the glareshield on either side of the guidance panel. The positioning of the standbys in the pilots’ line of sight is a vast improvement over the tiny standby instruments mounted lower on the instrument panel in older Gulfstreams. The standbys also replicate PFD symbology, which makes it much easier to transition from primary to standby instruments.
So far, so good, but touchscreen critics may still wonder why pilots need to adapt to this new technology. There are good reasons why it makes sense.
First, touchscreens eliminate a huge number of mechanical and electrical switches, removing many possible points of failure and simplifying flight-deck procedures. Going from dark flight deck to ready-for-engine-start in the G500 takes less than 10 minutes, about half as long as an experienced crew in a G550 (and far less than tyros during their first stint in a G550 simulator). Test and operating procedures are simpler, and there just aren’t that many switches to manipulate. And with three identical overhead panels that provide full access to all systems, two crewmembers can access different systems at the same time, if necessary.
An example of this functionality is a guarded switch. Physical guards take up more space and are necessarily more complicated. In Gulfstream’s touchscreen world, a guarded switch requires two touches, one to select the option and a second to accept the choice (this is the touchscreen equivalent of lifting the guard, then moving the switch). And the same can be done in reverse, too.
A second factor benefits the manufacturer and ultimately the aircraft owner/operator, and this is that touchscreens can easily be modified to add new functionality, without having to dig a new hole somewhere in the flight deck to install a new switch. Manufacturers and aftermarket modifiers invariably come up with improvements and new capabilities, and there will likely be regulatory mandates to install new equipment in the future. Adding the switches to control the that equipment is so much easier with touchscreens and software. “Removing the constraints of hardware is huge,” said Evans.
There is a third argument favoring touchscreen control in flight decks. Much of the post-flight checklist in a G550 involves putting switches back in the correct position for the next flight. With touchscreens, all this extra effort is gone. Just turn off the electricity, and the software tells the system how to behave when the electrons are reactivated for the next flight.
There is a single type rating for the G500 and G600 and no requirement for differences training, according to Evans. “Where we have differences, which is the amount of fuel and the thrust difference and physical dimensions, you learn it all in class.” The only way to notice the difference between the G500 and G600, he explained, is the larger fuel capacity carried by the G600’s longer wing.
Chief demonstration pilot Brian Dickerson highlighted some of the features during a walkaround of the G500 that we would be flying, P1, the first production version and the fifth one manufactured. It had logged 625 hours’ total time by the time of our flight.
A G500/G600 is easy to spot because the pilots’ side windows are swept back whereas on previous models they have a vertical-shaped aft edge. The new windows allow pilots to see the wingtips from the flight deck.
The electrically actuated cabin entry door doesn’t touch the ground when opened, and the G500 can be towed while the door is fully open. The door is designed so that when the pilot steps on the first step, the handrail is in the exact right spot. When the pilot alights at the top of the steps, the doorway relative to the steps eliminates the need to duck to prevent hitting your head on the doorway.
Like the G650, the G500 carries Honeywell’s IntuVue RDR 4000 3D weather radar, with an 18-inch antenna. SiriusXM satellite weather is an option, but that service is available only in the continental U.S. and large areas of Canada and Mexico.
On the outside of the airframe, access panels are placed at locations that allow teams to service systems in parallel, a typical Gulfstream philosophy. The fuel panel can be controlled from the flight-deck touchscreens.
Something that is included only on FBW Gulfstreams is a ram-air turbine, and that is pretty much the major difference in the electrical system compared with non-FBW Gulfstreams.
Both the hydraulic and engine oil systems can be filled from replenishing tanks inside the aft fuselage, something that pilots can do when maintenance support isn’t available.
The G500 wing measures 86 feet, 4 inches and is swept 37 degrees, and as is normal for Gulfstreams, the entire 30,250 pounds of fuel is carried in the wings. Also a Gulfstream norm is that when the center of gravity is within limits on takeoff, it will stay that way as the flight progresses. For such a large airplane, the G500’s typical Vref speed of less than 120 kias is relatively slow, especially taking into account that as on all other Gulfstream jets, its large, clean wing has no leading-edge devices. The flaps cover two-thirds of the wing trailing edge and extend to 39 degrees in the landing configuration.
The horizontal stabilizer is a trimmable surface, and there are no elevator trim tabs. During the functional check of the trim system, after the zero fuel weight center of gravity is input in the avionics, the stabilizer is automatically tested through its full range of travel then set to the correct takeoff setting.
The baggage compartment volume is 175 cubic feet and is accessible in flight up to 40,000 feet, although that is an FAA limitation and not an EASA limitation. Gulfstream is working with the FAA on eliminating that restriction.
The G500’s Pratt & Whitney Canada PurePower PW814GA engines each produce takeoff thrust of 15,144 pounds and they match the 50-inch fan diameter found on the G650’s Rolls-Royce engines. The PW814GA fan is a one-piece blisk, and the engine’s bypass ratio is 5.95 to 1. Its Talon X combustor helps the PW800 series deliver double-digit improvements over CAEP 8 emissions standards, and it also offers a double-digit noise margin compared with ICAO Stage 4 limits.
Prepping for Flight
The G500 was relatively light, loaded with 12,000 pounds of fuel for our flight, which was scheduled for 1.5 hours. Takeoff weight was 59,863 pounds, well below the 79,600 mtow. The avionics calculated V1 at 116, Vr 118, V2 132, and Vref in case of immediate return at 136 knots.
Without the limitations of a traditional FMS and its multiple deep-pages interface, the Symmetry design allowed engineers to get creative in how pilots interact with the avionics. For example, pilots start on the touchscreen in FMS mode, which mimics the traditional FMS inputs, although in a much simpler and more intuitive interface. Tabs along the top of the touchscreen make available just what is needed, such as FMS init, flight plan, perf init, perf takeoff, landing. In the perf takeoff tab, not only does the touchscreen show the runway required (3,928 feet) versus available runway (7,002 feet), but it does so with a little runway diagram with color bands highlighting the required amount of pavement, making it easy to determine whether there is enough runway or whether it is going to be marginal. Green bands are good. Other information on this screen includes V speeds, takeoff weight, power setting, and accelerate stop/go distances.
Once all the planning is done, switching to phase-of-flight mode brings up tabs for each phase of flight, including start up, taxi, takeoff, en route, and arrival.
The takeoff tab, for example, includes V speeds (which remain yellow until the aircraft is properly configured), autobrake control, obstacle and runway information, flight-plan departure and destination, and most handy, transponder setting and code and TCAS TA/RA switch. Being able to look down at the touchscreen to see all the information needed for the phase of flight—and that the checklist wants you to verify—makes so much more sense compared with earlier flight-deck designs. No more looking at three or four displays or FMS MCDUs; the information is consolidated on the touchscreen controller.
There is much more to the Symmetry interface, and learning it will not take pilots long as it is simple to understand and logically laid out.
The flight guidance panel, itself, is a vast improvement over those on earlier Gulfstreams, with a logical layout clearly marking and separating speed, lateral, autopilot, vertical, and altitude controls. Another pilot-friendly feature is that button lights are separate from the button, so a pilot can make a selection and instantly see the light switch on or off without having to lift a finger off the button to verify what the light is doing.
Before getting under way, it’s important for pilots to set up the armrest behind each sidestick. The armrest tilts fore and aft and can be moved up and down. The vertical adjustment is numbered, so pilots can remember their sidestick number for quick adjustments when switching seats or airplanes.
The nosewheel steering system switch (a physical guarded switch) and the pedal steering switchlight and tiller are in the normal place on the left side ledge, aft of the sidestick. But unique to the G500 is rudder pedal steering authority up to 40 degrees when below 13 knots, making the tiller necessary only in tight spaces. I never had to steer with the tiller during the flight, and steering with the pedals is far smoother and helped me avoid the sudden jerky movements that I sometimes cause when tiller steering a long airplane.
Taxiing the G500 is so much more pleasant with the pedal steering, and there is a new feature that Gulfstream is the first to implement in a new jet, Honeywell’s 3D Airport Moving Map, which makes taxiing more fun and vastly improves situational awareness. The new taxi display is part of Honeywell’s SmartView synthetic vision and it places the pilot in a virtual seat outside the airplane, a so-called exocentric view up and to the rear so it looks as though I’m viewing the airplane from above. This is even better than ordinary synthetic vision, especially the expanded taxiway and runway markings and signs, which pop up in 3D for the ones that are closest to the airplane. Only necessary information is included in the 3D taxi display, including groundspeed, which makes for a nicely uncluttered display.
On takeoff, once I advance the power levers more than 20 degrees, the display reverts to a normal 2D egocentric view.
It was a hot summer day in Savannah when I flew the G500. Dickerson suggested a soft touch with the sidestick, using two fingers to move it (he calls it a “soft banana”). The pilot’s muscles will impart a force to the stick if gripped too tightly, he explained. With sidesticks, pilots need to think about what to do with the hand that pushes the power levers forward after reaching V1—instead of trying to take hold of the nonexistent yoke—and he said the process for the G500/G600 is to drop your hand onto your inboard knee, or some pilots prefer to rest their hand on the CCD on the center console.
As the big Pratts kicked in strongly, the G500 accelerated rapidly, and at V1, I remembered to move my right hand to my knee. At rotation speed, I nudged the stick back a tiny amount and the G500’s nose lifted off, followed quickly by the rest of the airplane. I pulled the nose gently to 10 degrees and hand flew as we climbed away from Runway 01.
During the briefing before the flight, Evans, who captained the first flight of the G500, told me what to expect handling-wise. “It’s a hot rod,” he said, “a pilot’s airplane. It’s definitely a Gulfstream; it loves to go up, loves to go fast, and I love to hand fly it and hate to turn on the autopilot. It’s a rare experience.”
He was right.
From the moment the wings started generating lift and we lifted off, I could appreciate what Evans said. Although the FBW flight controls are the next generation of the G650’s flight-control system (with fewer remote electronic units, which improves reliability), the G500’s handling is even better. Only tiny movements of the stick are needed. But the stick also provides force-feel feedback to the pilot, one of the features of the BAE active sidesticks.
While trimming in flight, the trim indicator changes to show the trimmed speed, and any movement of the trim switch on the sidestick changes the trimmed speed, as indicated. On the ground or with the autopilot on, the trim switch sets the stabilizer setting in degrees, and this is color-coded green to indicate takeoff range. The autopilot disconnect button on the sidesticks doubles as a trim speed sync (TSS) button. This simplifies trimming by allowing the pilot when hand flying to automatically set pitch trim to 1 g at the current speed, with just a press of the TSS button.
I hand flew as we climbed to our first level-off at FL230; thunderstorms were popping in the airspace surrounding Savannah, and ATC was busy shepherding traffic into and out of the airport. Climbing north of Savannah, we leveled again briefly at FL310, then ended up at FL450 at Mach 0.90, 506 ktas, while burning about 1,300 pph per engine. Temperature was ISA -8 deg C. Cabin altitude was 3,800 feet, and it remains a low 4,850 feet at the maximum altitude of FL510. Evans said a typical climb directly to FL450 takes 17 to 18 minutes.
We swapped seats so I could experience the cabin and its incredibly low sound levels with the forward bulkhead door closed. There is a main entry door enclosure, which adds to the extremely low interior noise levels.
The 1,715-cubic-foot cabin in this G500 was configured with 13 seats in three zones, including two sets of double club seats forward, a three-seat divan opposite two club seats, and another two sets of double clubs around a single-pedestal table, which provides more legroom for occupants. Seat pitch is the same 105 inches as in the G650.
A credenza houses a 28-inch monitor, which folds flat so it doesn’t take up any drawer space. The galley is in the aft cabin—although it can be situated forward if the customer wishes—and features deep counters and drawers and a large trash container, thanks to the extra cabin width. There was plenty of room for a coffee pot and espresso machine, a convection oven, a microwave, and a real refrigerator.
A master control panel is available in the galley and also at the front of the G500. Gulfstream’s cabin-management system gives passengers control of lighting, window shades, the environmental system, and entertainment from touchscreen controls at each seat. The controls are hidden under sliding covers mounted in the side ledges next to the seats.
Back to Savannah
Of course, I had been flying using the head-up display, which is Gulfstream’s latest higher-resolution EVS III and HUD II system.
Now that the G500 is FAA and EASA certified, Gulfstream also gained approval for EVS-to-land operations with EVS III, which means that properly trained pilots with a letter of authorization can fly an approach, then touch down and roll out solely by reference to the HUD, with visibility as low as 1,000 feet RVR.
The thunderstorms were splashing a multicolored picture on the RDR-4000 radar overlay on the moving map as we descended toward Savannah. As soon as we descended below RVSM airspace, I switched off the autopilot to get some more hands-on time, which didn’t surprise Dickerson and Evans at all.
At the time that I flew the G500, it was not yet certified, and there was a strict limitation to avoid any lightning strikes, so we had to give the storms a wide berth. ATC vectored us all over the Georgia skies while we tried to find a relatively clear path to the airport.
We finally ended up flying offshore to the east and then flew back for an RNAV approach to Runway 28 at Savannah while the bulk of the storms roiled to the north.
This is a situation where having autothrottles is a real benefit; with constantly changing altitudes it was easy to keep my head outside the flight deck and focus on flying the airplane while the autothrottles automatically adjusted power to maintain the airspeed set on the guidance panel.
Flying the G500 around multiple heading and altitude changes was a pleasure; the stick responded instantly to my every nudge, and it felt comfortable using just finger pressure to fly this responsive jet. The level of precision available with FBW flight controls is unsurpassed, and Gulfstream engineers have managed to design an airplane that pilots will love and that maximizes comfort for passengers.
Dickerson briefed me that the landing, in typical Gulfstream fashion, requires care to avoid trying to flare and finesse the touchdown. That big flat wing and the massive flaps will cause a fat balloon of lift if the pilot pitches too high before touchdown. He recommends flying right down to the runway and at 20 feet lifting the nose just a degree, then letting it fly right onto the runway.
We dialed in an extra few knots on the Vref for the gusty winds, so it was set at about 124 kias.
Visibility was fine as we trundled down the glidepath, and flying with the HUD helped me nail the approach.
As we cleared the fence and dipped down to the runway, I focused on keeping the nose down and resisted the urge to put a little back pressure on the sidestick. The G500 responded perfectly when Dickerson agreed that we were low enough, and I gave the stick a tiny pull. Then the main wheels touched smoothly, followed by the fuselage dropping gently onto the nosewheel. A touch of reverse thrust as the autobrakes caught hold—we had set them to medium—and the G500 quickly slowed to taxi speed.
With full weight on wheels and below 60 knots, the synthetic vision automatically reverts to the exocentric 3D Airport Moving Map, a handy feature that pilots will appreciate, especially at an unfamiliar airport. I taxied back to the Gulfstream ramp—no tiller needed—and we shut down.
Gulfstream’s newest jets, the G500 and G600, are arguably among the most advanced business jets ever developed. After two hours flying the G500 (a little longer than planned thanks to the thunderstorms), I have no doubt that pilots, especially those with Gulfstream experience, will instantly feel at home in these airplanes. They may even feel that the initial training time is too long, because once they get used to the FBW sidesticks and the touchscreen interface, other than a big step up in performance, there is little new to learn.
The G500, with certification now in hand, will enter service later this year, and the G600 is expected to achieve certification by the end of 2018.
Gulfstream’s FBW Philosophy
Gulfstream engineers aim for a pilot-in-the-loop philosophy, and this means that Gulfstream’s fly-by-wire (FBW) design, while it includes protections for slow- and high-speed flight, gives the pilot full control over the flight envelope. The protections include angle-of-attack limiting, high-speed protection, maneuver load alleviation, speedbrake auto retraction, dynamic rudder limiting, and elevator split load limiting.
The flight-control system is a speed- or trim-stable design, which means that the controls act like those of a non-FBW airplane, and when hand flying, the pilot must manipulate the controls to position the attitude as desired then trim to maintain that attitude. Without trimming, the airplane wants to return to the trimmed speed. For example, if the G500 is trimmed to, say, 200 knots, and the pilot pulls back and slows to 180 knots, the stick will feel heavy until trimmed to the new speed, just like an airplane with mechanical or hydraulic controls. In other words, stick forces vary according to the dynamic forces on the control surfaces and also if the other pilot is trying to move his or her stick, just like interconnected mechanical controls on traditional airplanes.
There are four FBW modes: normal, alternate, direct, and backup, but only the normal mode is available to the pilots. The other modes kick in when certain equipment losses occur, and there is no way to force the FBW into the other modes. For example, if at least one inertial reference system (IRS) isn’t agreeing with one AHRS, the system degrades to alternate mode. The same occurs if there are aren’t at least two valid IRSs. If these conditions are fixed, the FBW automatically returns to normal mode, or the pilot can push the flight-control reset switch to return to normal mode.
In alternate mode, the autopilot no longer works and other functions are degraded. More features are unavailable in direct mode, which involves invalid signals from all four flight-control computer channels, and from this mode, the controls can’t be returned to alternate or normal mode. In backup mode, the backup flight control units communicate directly with flight controls on a separate bus.
FBW flight controls must meet stringent certification requirements. Alternate mode probability of occurrence is less than one per 10 million flight hours while backup mode probability is less than one in a billion per flight hour.
Having flown a few FBW business jets, I don’t think about the fact that I am just sending an electronic request to computers that tell the flight controls how to deflect; what I do is just fly the airplane, and the G500 responded precisely and pleasantly in all regimes and configurations. Whether at high altitude or low, the controls felt comfortable and responsive, and the simulated control feel in the active sidesticks is tuned to help make the G500 feel Gulfstream-like in all regimes, although it definitely does not share the heaviness of the controls of the G550.
“Fly-by-wire allows us to tune that experience and make it be more precise,” said Scott Evans, director of demonstration and corporate flight operations. “The airplane feels the same when hand flying at FL490 or 500 feet on approach or throughout the speed regime. It’s comfortable to fly. Our approach to fly-by-wire is that it’s a design philosophy, with pilots being in the loop. That’s core for us; pilots are the best safety tool. We want them to be able to feel [the airplane], with positive speed stability, not neutral speed stability. The airplane can talk to you and tell you, if it’s slow or fast, we get a heavy hand, and it naturally brings us in to scan the speed.”
The goal was to make the pilot feel in control and that they are flying a Gulfstream, but a big difference is the lesser amount of displacement of the controls. “We already fly one-handed,” Evans explained. “That hasn’t changed. All we’ve done is change the reach model and the amount of displacement you have in the control. It’s not 60 degrees, now it’s 10 degrees. What you will find is it will take less than a minute for your brain to figure out that I don’t need this much roll [movement] to get the same level of aircraft response out of the stick. Your brain figures out how much displacement you need to get that response. It’s an extremely natural event. You will find it intuitive.”
“Watching people in the [lab] simulator and seeing the transition, it’s amazing how quickly they adapt to it,” said Mark Kohler, vice president, Advanced Aircraft Programs.
The active-control sidesticks (ACS) design was carefully thought out and tested in the Gulfstream lab simulator. “We designed the inceptor [sidestick] to be an extension of ourselves,” said Evans. “It’s designed so that it’s at the natural reach position.” When a person’s arm rests on a table, the hand naturally tilts about 20 to 25 degrees inward (toward the fingers). Also, when reaching away from the body, the arm doesn’t go straight out, but moves away from the ribcage, he explained. So the sidestick is tilted inboard 20 to 25 degrees, to match the lower amount of strength when moving the stick outboard as compared with inboard (about a 30 percent difference), and it is toed outboard about three degrees. This all helps make moving the stick side to side feel exactly the same, whether inboard or outboard (depending on which seat the pilot is flying from) and prevents fore and aft movement of the stick from causing a roll change or vice versa.
Gulfstream had been looking at sidestick design even during the G650 development, but wanted active sticks that moved together instead of the flight-path stable design where sticks are passive and don’t move together. “For a decade we wanted to do sidesticks,” said Evans. “It’s our office and our dining room, especially in an 11- to 13-hour airplane. Any space gain is positive. [We can] have a desk, and there’s no occlusion of displays. Sidesticks reduce weight and increase reliability. There are lots of benefits. But we would never, ever do a passive system, because we felt strongly that it was a loss of situational awareness between [the two pilots]. If I’m behind the airplane, you can see that. In a passive system you don’t see that until you’re behind the power curve. Not only is the stick moving with our input, but it’s also responding to the autopilot, just like the autothrottles. It’s always building on things that are positive in a design.”
About three years into the G500/G600 development program, the Air France 447 stall accident happened. “When we read the accident report,” Evans said, “it made us feel validated in our choice of the active control sidesticks. In some incidents, a passive sidestick didn’t allow for immediate recognition of the event. We feel confident we made the right decision for us as a company in protecting our brand and customers.”
In a traditional airplane, he explained, “As pilots, that’s how we always respond. If we’re both on the [controls] and fighting, one calls ‘my airplane’ and the other becomes pilot monitoring. We wanted to maintain that exact thing. By having that same feedback, even though the sticks are electronically linked, you’re not pressing a button to take control or relying on a CAS message. Somebody calls ‘my airplane’ and one assumes the monitoring role. You don't have to [fly] any differently to get the benefits of fly-by-wire.” And training is the same, too.