Gulfstream's G550 aims to guarantee making New York-Tokyo a non-stop flying experience, a boon to business travellers who absolutely have to be there on time...
The world's first ultra-long-range business jet, the Gulfstream GV, gave operators the ability to fly New York to Tokyo non-stop. While its 12,000km (6,500nm) range with eight passengers at Mach 0.8 was sufficient for most trips, unseasonably strong headwinds could force a refuelling stop. Gulfstream's newest flagship, the G550, traces its routes back to the GV and its GV-SP derivative, and is designed to make New York to Tokyo more of a sure thing regardless of headwinds.
The G550 was introduced at the 2002 National Business Aviation Association (NBAA) annual meeting and convention, when Gulfstream unveiled a new seven-aircraft product line. Previously designated the GV-SP, the G550 offers customers more range than the GV, while featuring significant improvements to the cabin and avionics package. After a four-year development, Gulfstream received US Federal Aviation Administration type certification for the G550 in August 2003, with European approval following last month.
The overall exterior dimensions and mould line of the G550 are identical to the GV's, but Gulfstream has made numerous refinements to reduce cruise drag. The most visible evidence of the drag reduction efforts is the addition of 25-30mm (1-1.25in)-thick contoured shapes on the inboard 3.8m of the wing's trailing edge. Called trailing-edge contours (TEC), they move the lift inboard, increasing span efficiency while reducing compressibility drag towards the wing tips.
On the forward fuselage, the pressurisation outflow valve has been altered to capture the thrust of the exhaust airflow. Improved rudder and elevator seals help to reduce drag over the empennage, while changes to the auxiliary power unit and equipment cooling system shield further reduce drag. Realignment of VOR and localiser antennas, and use of conformal antennas, further contribute to the overall drag reduction. These efforts combine with improved fuel efficiency from the Rolls-Royce BR710 engines to give an additional 135km of range over and above that of the GV, now 12,500km at M0.8 with eight passengers.
In the forward cabin the cockpit jumpseat has been relocated and an auxiliary radio rack eliminated, allowing the forward entry door to be moved forward 0.6m (2ft). This has freed an additional 1.6m3 (58ft3) of cabin volume, and allowed an extra Gulfstream signature oval window to be added in the forward fuselage, for a total of seven a side. The extra space has been put to good use, allowing the cabin to be configured into four distinct living areas.
Customers have the choice of either a forward or aft galley layout. The forward galley option offers the longest living area, 6.54m, and 34.1m3 of volume. Up to 19 passengers can be accommodated, with typical configurations seating between 12 and 18 passengers. The in-flight accessible baggage compartment has 6.4m3 of space; a 25% improvement over that of the GV, made possible by reconfiguring potable water and vacuum lavatory system tanks.
While the passengers will enjoy the extra cabin windows, the most significant additional window on the G550 is the one on the lower portion of the radome, for the Kollsman-developed All Weather Window. This is an infrared (IR) sensor and is the heart of the G550's enhanced vision system (EVS). A cooled indium antimonide (InSb) staring sensor array (320 x 240 pixels) is mounted on the forward pressure bulkhead and provides an IR image of the forward external environment. The InSb array detects energy with wavelengths of 1-5µm, commonly called the near and medium IR bands. Due to the atmosphere's chemical composition, there are only portions or windows of the 1-5µ spectrum that allow enough transmissivity to see the IR environment for any significant distance. The EVS sees in two of these windows, 1-2µm and 3-5µm. Approach and runway lights are visible in the lower wavelengths, while background terrain is sensed in the higher ones. IR data is captured by a video camera and displayed in the cockpit on either the HUD or one of the flat-panel multifunction displays (MFD). In general, rain or smoke does not degrade IR performance. While high levels of absolute humidity (dense fog) will degrade performance, the EVS will still see far beyond the range of the unaided eye.
Enhanced cockpit
Perhaps the biggest improvement the G550 offers over the GV is in the cockpit, where Gulfstream has introduced its PlaneView flightdeck. Based on Honeywell's Primus Epic avionics suite, PlaneView will become the standard cockpit on all Gulfstream models from the G350 upwards. The G550's forward instrument panel is dominated by four 355mm liquid crystal displays in landscape format.
Pilot interface to the avionics suite is through either of the sidewall-mounted cursor control devices (CCD) or three centre console-mounted multifunction control display units (MCDU). The glareshield has a central guidance control panel, with display controller units on either side. In general, cockpit layout, including the overhead panel, is nearly identical to that of the GV. Gulfstream's visual guidance system (VGS) rounds out the major improvements the G550 offers over the GV. The heart of the VGS is a Honeywell HUD2020 head-up display. The HUD has a 30 x 25° field of view and is used to present flightpath information as well as the EVS's IR picture.
The PlaneView system is built around three modular avionics units (MAU). Each MAU has slots for various system cards, ranging from communication/navigation transceivers to GPS and air data systems. The G550's three MAUs provide a high level of redundancy, some competing business jets having only two. In addition, the modular design allowed the auxiliary radio rack to be removed from the cabin while providing for significant future growth and upgrades. Three standalone Laseref V inertial reference units and dual HF radios round out the G550's comprehensive avionics suite.
Improvements
While initial certification for the G550 is complete and 11 production aircraft have been delivered, Gulfstream is in the middle of developing and certifying follow-on improvements. Flight International was given the opportunity to sample the G550 and its PlaneView cockpit at Gulfstream's Savannah, Georgia production and test facility. The aircraft for the test flight was the original GV-SP testbed, a modified GV. "T1," as it is called by Gulfstream, has all the aerodynamic and avionics improvements offered by the G550, but has a flight-test cabin layout with only six windows on each side.
For the flight, I was accompanied by Gulfstream senior experimental test pilot Tom Horne. During the pre-flight walk around inspection I was struck by the size of the G550's wing. With an area of 105.6m2, the G550 has a maximum wing loading of only 390kg/m2 (80lb/ft2), much less than the 454kg/m2 of the rival Global Express. Horne pointed out some of the differences between the G550 and its GV predecessor. As mentioned, the wing trailing edges were the most prominent change. Additionally, the vortex generators on the winglets have been relocated - moved up higher towards the wingtips.
The inspection itself was straightforward, with all required items accessible from ramp level. Stairs are incorporated into the hydraulically actuated forward entry door, which features a single mechanical seal. On production aircraft the passenger cabin is isolated from the entry door by two sliding doors, one parallel to the fuselage just inboard of the entry door and one that acts as a divider between the crew area and passenger compartment.
Horne started the APU as I strapped into the four-way adjustable seat. There was ample storage space for flight publications in sidewall bins as well as aft of the crew seats. I used the centre-pillar coloured alignment balls to reach a comfortable seating position. Next I unstowed the HUD from the ceiling and turned it on to ensure my seated position was at the design eye position for the VGS.
Horne talked me through the initialisation procedures for the flight management system (FMS). Unlike Dsssault's Falcon EASy flightdeck, which almost exclusively uses pull-down menus and CCDs for data entry, PlaneView allows the pilot to use either pull-down menus or the MCDU. For a pilot transitioning from a typical glass cockpit, the MCDU interface would seem to be the more familiar and perhaps easier to use.
The sidewall-mounted CCD is arranged like an armrest, the thumb slew button falling easily to hand. Above the slew button are three buttons that designate the display in which the cursor will operate. With the displays numbered 1 to 4 (left to right), the pilot can move his cursor to displays 1, 2 or 3. The co-pilot can operate in displays, 4, 3 or 2. The primary flight display (PFD) for each is the outboard display, 1 or 4 for pilot and co-pilot respectively.
Full screen
As with the EASy displays, the PlaneView can be configured in either a full screen or 2/3-1/3 lateral segmented window format. The PFD has the standard ADI on top and HSI below. Flight director commands can be displayed as either a "V" bar or as split cue bars. In the segmented windowformat, the PFD takes up 2/3 of thedisplay, while the remainder can be used to present system displays or uplink weather information.
The two centre displays typically function as MFDs, used to display synoptic pages, cautionary advisory messages, checklists, moving map or electronic charts. For dispatch, only three displays are required, and standalone checklist controllers on outboard side consoles allow the CCDs to also be inoperative. Like the checklist on the Falcon EASy, the G550's is merely an electronic rendition of a paper one, not one that senses current switch or system status.
After the pre-start checks were completed, both engines were started, one at a time, with bleed air from the APU. The start sequence can essentially be automatic, the FADEC determining when to add fuel and initiate ignition. Since our aircraft had recently landed from another sortie, the engines needed to be thermally stabilised before ignition. In many engines the fan rotors have a tendency to bow after shutdown as heat rises to the top of the engine case. Unless the engine has just been shut down or fully cooled, it is advisable to motor the engine for 30s before ignition. Each engine reached an idle N2 of 62.6% about 1min after initiation of the start sequence. Horne led me through the post-start flows, saying just to turn off all the yellow lights on the overhead panel.
Graphic position
During the taxi from the ramp to runway 18 for take-off, our position was graphically depicted on the airport diagram chart, shown on the No 3 display. While Savannah is a relatively uncomplicated airport, the positional display should be a great taxi aid at busy fields or in low-visibility conditions. Additionally, proper use of this capability should reduce runway incursions or take-off attempts from the wrong runway.
During the taxi I found the tiller-controlled nosewheel steering allowed me to easily negotiate 90° turns. The rudder pedals gave ±7° of nosewheel steering , which was more than sufficient to track centreline on straight portions of the taxiway. Horne set the flaps to 20° in preparation for take-off. With a zero fuel weight of 21,180kg (46,665lb) and 4,470kg of fuel, the FMS computed a V1 of 114kt (210km/h), VR of 117kt and V2 of 122kt.
Once on the runway, I released the brakes and advanced the throttles to a mid-range position. I used the throttle- mounted buttons to engage the autothrottles, which smoothly advanced the engines to the take-off EPR setting of 1.56. As the aircraft rapidly accelerated through 80kt, I released the nosewheel steering tiller and took the yoke from Horne. About 20kg of aft yoke force was required to establish the initial take-off attitude, and the light aircraft leapt off the runway 12s after brake release and a ground run of less than 800m. Once airborne, a 25° nose-high pitch attitude was required to climb at the trim speed of 150kt. Gear and flap retraction caused negligible changes in yoke forces as the aircraft was accelerated to an initial climb speed of 250kt.
I engaged the autopilot in the VNAV (vertical navigation) mode for the climb to the G550's ceiling of 51,000ft/FL510. The climb was conducted in two segments, due to air traffic control restrictions. A climb speed of 250kt was held until the first level off at FL230, just 6min after brake release. The second climb segment from FL230 to FL510 started at M0.75 and took an additional 21min. Rate of climb until passing FL450 averaged 2,700ft/min (13.7m/s), the last 6,000ft alone taking about 12min.
Once level at FL510, I used the power command bar displayed in the PFD to accelerate to and maintain M0.8, the recommended long-range cruise speed. At 187kt total fuel flow was 910kg/h as the 24,585kg aircraft maintained 453kt.
As a rule of thumb, Horne suggests that FL510 is the optimum cruise altitude for gross weights less than 26,310kg. While still at FL510 I was able to perform a series of 45° angle of bank turns at M0.78. The aircraft's nose tracked smoothly across the horizon and there was no airframe buffet, even at this high altitude.
With an endurance exceeding 14h, the cabin environment can be just as important as aircraft handling qualities. The G550 has three temperature zones, allowing cabin comfort to be tailored to individual needs. The G550's pressurisation system is automatic, taking departure, cruise altitude and destination airport elevation information from the FMS. The cabin is pressurised during the climb to a maximum differential of 0.7bar (10.16lb/in2), giving a cabin altitude of only 6,000ft at FL510. Unlike some aircraft, the G550 does not recirculate cabin air in an effort to reduce engine bleed-air demand. While there is no doubt a small range penalty associated with increased bleed-air usage, the passengers will certainly appreciate a cabin-air environment that is refreshed every two minutes.
Next I used the flight level change (FLCH) mode of the autopilot to descend the aircraft to FL450 and accelerate to M0.87/237kt. Total fuel flow increased to around 1,400kg/h as the aircraft held 499kt. At M0.87, the published NBAA range with eight passengers is 9,260km. Slowing to M0.85 increases published range to 11,110km, allowing the G550 to make London to Los Angeles non-stop against 85% annual winds.
While level during the cruise at FL450, Horne had manually started to raise the cabin altitude to demonstrate the emergency descent mode (EDM) of the autopilot. As cabin altitude passed 7,900ft, the EDM was triggered. The autopilot rolled the aircraft to 90° off the original heading and lowered the nose to initiate a descent. The autothrottles, not engaged at the time, woke up and retarded the engines to idle. The autopilot then varied the descentattitude to maintain MMO/VMO (M0.885/340kt). Rate of descent averaged 30.5m/s. During the descent I manually deployed the speed brakes, which caused a slight pitch heave and increased the rate of descent to 45.7m/s.
Left to its own devices, the autopilot would level the aircraft at 15,000ft and maintain 250kt, but I disengaged the autopilot passing FL230 to sample the dutch roll mode at VMO. Aircraft response to a sharp symmetrical rudder input with the yaw damper on was quickly dampened out. With the yaw damper off, a similar rudder input revealed a lightly damped snakey aircraft response, the nose of the aircraft oscillating from side to side with little resultant rolling motion. Turning the yaw damper back on quickly damped out the yawing motions. One unique aspect of the G550's autopilot is that it can be engaged with an inoperative yaw damper, a feature that could lead to increased dispatch reliability.
I continued the descent to 10,000ft to sample the G550's slow-speed flying characteristics. The first stall was in a clean configuration, gear and flaps retracted. I slowed the 24,270kg aircraft in idle power at slightly less than 1kt/s. I stopped trimming in the pitch axis at the VREF of 134kt. Slowing through 124kt an amber pitch limit indicator (PLI) was displayed on the PFD to indicate the maximum safe pitch attitude. At 110kt the stick shaker activated. Continuing to hold aft stick pressure, the stick pusher activated as the aircraft slowed through 100kt. Increasing stick back pressure overcame the pusher and allowed the aircraft to fly a rock-steady wings level descent. Releasing aft stick pressure and advancing the throttles effected recovery to normal flight conditions.
Stall recovery
The PLI provided a graphic cue as to how aggressively the nose could be raised during the recovery, while avoiding a secondary stall. The second and final stall was in a landing configuration, gear down and flaps 39°. As was the case with the clean stall, stick-shaker activation, now at 91kt, and pusher activation, at 86kt, were not preceded by any aerodynamic warnings. Lowering the nose and advancing the throttles again effected recovery to normal flight conditions.
During the return to Savannah, as well as on the initial departure, I was able to exercise the G550's interactive navigation(I-NAV) capabilities. The heart of the system is a scalable moving map, which, like that in the EASy flightdeck, is designed to increase situational awareness by presenting critical information on as single display. Using a pull-down menu, data such as the underlying terrain, route, airport, navigation facilities, opposing traffic and weather radar returns can be displayed. ATC-directed routing changes were easily accomplished using the CCD and I-NAV display to graphically alter the route. While these same changes could be accomplished using the MCDU, I found the graphical interface more intuitive and easier to use.
As Horne called up the RNAV approach to runway 27 approach at Savannah, I unstowed the HUD and familiarised myself with the EVS display. Darkness had fallen, and while I could see the lights of Savannah in the distance, the EVS provided a vivid picture of the coastline and city. Horne displayed the approach chart in the No 3 screen while I briefed the approach. This approach chart, like several others for Savannah, is geo-referenced, allowing the aircraft's airborne position to be shown on the chart display. While this is an improvement over a paper chart, there are no technological reasons why the approach procedure could not be integrated into the I-NAV display. Making the approach procedure a part of the I-NAV display would reduce pilot workload while increasing situational awareness by allowing the pilot to concentrate on one display rather than two.
Approach advances
Two technological features of the G550 combine to enhance its ability to safely execute approaches in adverse weather conditions. The first is the ability to fly selected non-precision approaches using a VNAV descent profile. For our approach to runway 27, the standard minimum descent altitude (MDA) is 530ft above the touchdown zone elevation (TDZE). Using a VNAV descent profile the MDA is 370ft above the TDZE, 160ft lower. In addition to allowing for descent below lower clouds, the VNAV approach profile is easier to fly as the aircraft is flown in a stabilised manner down an FMS-generated glide path.
The second and perhaps greater approach aide is the EVS. In Januarythe US FAA authorised all aircraft with suitable enhanced flight vision system equipment, such as the G550's Kollsman-developed EVS, to descend on approach below the MDA or decision height as long as the appropriate lights or runway features are visible using the EVS. Descent is allowed to 100ft above the TDZE, at which point the runway features must be identifiable with natural vision to allow further descent and landing.
I left the autopilot and autothottle engaged for the approach to runway 27, which allowed me to concentrate on the EVS presentation in the HUD. The autothrottle precisely maintained the target speed of 116kt for the 23,130kg aircraft with flaps set to 39°. While there was more than 16km visibility and no clouds, theIR images of the runway edge identifier lights and VASI were clearly visible in the HUD. At 100ft above the TDZE, 150ft above mean sea level, I turned off theEVS display with the yoke-mounted thumb switch, allowing me to see the natural lighting environment alone. I disengaged the autopilot and autothottle and executed a low approach, advancing the throttles as Horne selected the go-around flap setting of 20°.
Slow approach
Following ATC vectors, I climbed the G550 to 2,500ft MSL for a hand-flown RNAV approach to runway 18. In the pattern I found the G550 a delight to fly. The large wing and relatively low weight combined to give a remarkably slow approach speed (116kt) for an aircraft with a fixed wing leading-edge. Descending through 100ft above ground level on final approach, I retarded the throttles to idle, and initiated the flare manoeuvre at about 20ft. The main gear touched down softly, and I held the nose wheel off the runway and advanced the power to complete the touch and go manoeuvre.
The third and final approach was another hand-flown RNAV one to runway 18. The G550's landing-gear geometry gives it a noticeably nose-down attitude in a three-point stance. Much like with the McDonnell Douglas DC-10, the pilot must fly the nosewheel to the runway after main gear touchdown. The spoilers automatically deployed on touchdown when the throttles were retarded to idle. Mid-range thrust reverse and light toe braking were used to slow the aircraft to taxi speed before turning off the runway 1,200m from the approach end. Taxi back to the ramp and post flight shutdown procedures were easily accomplished.
Range leader
During my 2h flight, I was able to take the G550 to the edges of its flight envelope, where it showed itself to be a delight to fly. The PlaneView cockpit with its graphical user interface made establishing and maintaining situational awareness easy.
A number of seemingly small incremental refinements has given the G550 465km greater range than the GV. The EVS may allow approach and landing in weather that would otherwise require a divert after a globe-spanning flight, or outright cancellation of the trip. Gulfstream defined the ultra-long-range business jet segment with its GV, and the G550 looks set to maintain its leadership.
MICHAEL GERZANICS / SAVANNAH, GEORGIA
Source: Flight International
