Peter Henley/WITCHITA
Bombardier's Global Express offers a combination of range, speed and cabin size claimed to be unequalled by any other business jet, a result of designing an aircraft from scratch for the ultra-long-range mission.
The Global Express sits at the top of a range of Bombardier business jets which encompasses the entry-level Learjet 31A, mid-size Learjet 60 and large Challenger 604, plus corporate variants of the Canadair Regional Jet.
Bombardier had three design goals for the Global Express: to offer the longest range and highest speed of any corporate aircraft; to provide the largest and most flexible cabin of any purpose-designed business jet and to guarantee high despatch and mission reliability.
The aircraft has been designed to carry eight passengers and four crew 12,040km (6,500nm) - nominally New York to Tokyo - cruising at Mach 0.8 and 51,000ft (15,500m). Maximum cruise speed is M0.89. Good airfield performance was equally important, and take-off field length is 1,750m (5,750ft).
These ambitious performance targets required an advanced wing and new engines. The 20.6m-span, 35°-swept wing has a supercritical aerofoil, winglets, multi-section leading-edge slats and trailing-edge flaps, and multifunction spoilers. The twin engines are 66kN (14,750lb)-thrust BMW Rolls-Royce BR710 turbofans. From a systems standpoint, the Global Express has been designed to meet the requirements of airline-standard extended twin-engined operations.
The programme was launched in December 1993 and Canadian certification was received on 31 July. Development has cost Bombardier and its risk-sharing partners $800 million. The company forecasts a potential market of 550-800 long-range business jets by 2010, but has based the programme on a "conservative" estimate of 250 sales - 80 are on firm order and the Global Express is expected to enter service early next year. Flight International was invited to fly the Global Express from Bombardier's Wichita, Kansas, flight test centre in late July. The 2,200h development and certification flight test programme, which involves four aircraft, has the aim of gaining concurrent and integrated Canadian, European and US certification.
The day before the flight, a comprehensive cockpit briefing and a short simulator session were provided at the Bombardier training centre at Montreal. The Global Express simulator has been built by CAE Electronics in step with the prototype aircraft, is now at the same development state as the aeroplane and will be certificated at or about the same time.
Having the simulator so early in the programme has been a great asset, says Terry Yaddow, director of customer training for business aircraft, because the certification authorities, training captains and potential customers have been able to sample the Global Express without putting an extra load on the development and certification flying programme. Test and training pilots have been able to share views on operating procedures and Bombardier has gained an early market reaction to the cockpit, flight and system management systems.
The simulator proved to be an ideal training aid for someone like me needing an introduction to flying the aircraft. The menu of synoptic pages that can be selected on the engine indicating and crew alerting system (EICAS), for example, provides a guide to systems layout and operation that is far more comprehensible than diagrams in a training manual.
It is probably the integration and management of the systems that makes the biggest first impression with the Global Express. The cockpit is crisply and neatly designed around the six 200 x 180mm (8 x 7in) screens of the Honeywell Primus 2000XP avionics system. These are mounted horizontally across the instrument panel, with the standby attitude indicator and altimeter placed centrally.
It looks as if much thought has been given to laying out the cockpit and making it user friendly for the crew, which could be occupying it for 12-13h on a 12,000km flight. Senior experimental test pilot Craig Tylski, with whom I flew the Global Express, says there was considerable pilot input when the cockpit layout was evolved. Equally obvious was the fact that Bombardier and Honeywell software engineers have expended a lot of development effort to achieve the sophisticated level of systems management that is provided.
CULTURE CHANGE
Adapting to the Global Express' automatic control of systems could clearly be a culture change for pilots with thousands of hours in a dials-and-switches cockpit. It will also be important for pilots to avoid complacency and to sustain a high level of systems knowledge to react logically and correctly should a serious systems failure ever occur. Systems awareness will be emphasised during periodic currency training in the simulator, Bombardier says.
The first prototype Global Express, aircraft 9001, was used for the flight. It is still very much a development aircraft, with a long air-data probe on the nose and a remote static-source cone tucked up under the fin and deployed from a drum at the rear of the cabin. The cabin contains the usual flight-test crew positions and water ballast tanks used for development flying. An attitude recovery parachute is mounted in the tailcone and an emergency exit is built into the cabin floor just behind the cockpit.
The cockpit of aircraft 9001 (registered C-FBCX, reflecting its Canadian origins) is also non-standard. Some of the automatic systems require manual operation, there is a G meter on the coaming above the captain's left hand and angle-of-attack and sideslip indicators, both connected to the nose probe, are mounted above the central coaming. A flat screen folded beneath the glareshield can be latched down to display flight test parameters, but obscures the two middle flight instrument screens when in use. The control yokes have been modified to take calibration equipment.
The seats, however, are to production standard, having adjustment fore and aft and for height and recline, as well as fold away armrests adjustable for height and five-point harnesses. Entering or leaving the seats involves stretching across the seat cushions because the centre console fills the gap between the seats. The rudder pedals can be adjusted for reach via a small crank handle between the pilot's ankles. There is storage space in the captain's side console for a headset or a Jeppesen-style chart book, but not for a flight bag. An emergency oxygen mask is installed in the side console and the "spade handle"-shaped tiller located at the forward end of the console came easily to hand.
The field of view was good except that, in a turn, the top of the side window began to cut off the view sideways at or above about 30í bank. Each pilot could just see the wing tip on his side, but only by leaning towards the side window and peering aft.
The aircraft was connected to a ground power unit while Tylski entered the flight plan details in the flight management system, using a controller on the centre console, and flight test engineer Scott Runyan prepared his test console in the cabin. The AlliedSignal RE220 auxiliary power unit (APU) was then started by the simple expedient of turning to "start" the solitary switch on the APU controller at the lower edge of the overhead panel. The APU start was automatic, and shutdown would have been automatic had a malfunction arisen. Provided the pre-start checks have been completed in accordance with the checklist, the APU generator and bleed air will then come on line automatically, powering the aircraft electrical buses and providing air for cabin conditioning and main engine starting.
The BMW Rolls-Royce BR710-A2- 20/01 engines are two-spool turbofans with a bypass ratio of about four. Each is controlled by a dual-channel full authority digital engine control (FADEC) system, which is powered by a dedicated engine-mounted generator. Engine starting, like that for the APU, is fully automatic with an automatic abort should a malfunction occur. The start is initiated using a simple switch to the rear of each engine power lever on the centre console. Global Express 9001 does not have the auto-throttle that production aircraft will have, but the engines and FADECs are otherwise to production standard.
Each engine, during early rotation, produced an audible rumble and noticeable vibration. I was told this was because the engines were still warm from the previous flight (which had finished 45min to an hour earlier), and that warm starting could cause a so-called "rotor-bow". BMW R-R says the rotar bow phenomenon is a result of the design of the BR710, and is handled by the FADEC. The engine manufacturer believes the noise and vibration I observed was amplified by the green aircraft's unfinished interior.
STEP-BY-STEP PROGRESS
Throughout these starting procedures, the EICAS illustrated progress step-by-step. Of the six displays in front of the pilots, the outboard two on each side are flight instruments while the two inboard screens are used for EICAS and system displays. (The displays can easily be switched from screen to screen to cater for failures.) The EICAS display (normally the inboard screen on the captain's side) shows engine parameters. Engine pressure ratio, fan and gas-generator speeds and inter-turbine temperature (ITT) have both analogue and digital presentations, while oil temperature, pressure and fuel quantity are digital.
Configuration diagrams - for undercarriage, flaps, tailplane incidence and control-surface trim positions - appear in the lower right of the EICAS display. Above these is a vertical box in which crew alert messages (CAMs) are shown. CAMs are used primarily to advise of any changes to, or incorrect, systems status (for example, take-off configuration if the parking brake is on, or the failure of a generator). Routine messages appear in blue or white letters, those requiring crew attention in amber and vital messages in red.
The inboard screen in front of the co-pilot, meanwhile, is used for systems synoptics. There is a menu of eight to chose from. The one most often used is the EICAS secondary display, which shows cabin temperatures and altitude, crew oxygen, oil quantities (for the engines and APU), wheel brake temperatures and fuselage door status. The other options are the AC electrical, DC electrical, fuel, bleed air and anti-ice, flying controls, air conditioning and hydraulic synoptic pages. Each of these shows systems coming alive as valves automatically open and pressures rise - or the automatic corrective action the management system is taking to rectify an abnormality.
If a generator failed, for example, a CAM legend would appear on the EICAS display and the crew could select the AC electrical synoptic page on the other screen to view load transfers or to confirm that the corrective procedure had been completed automatically. There is an audio warning for events warranting the crew's immediate attention, and red and amber "attention getters" are mounted on the glareshield in front of each pilot. During engine start and shutdown there were transient red and amber warnings as systems came on line or ran down, but these could not be classed as "nuisance warnings" because the smart software cancelled them after a second or two - and the audio was not triggered.
I flew C-FBGX from the left seat. Taxiing the Global Express was a pleasure. The parking brake, to the rear of the control console, is released by pressing a latching button and rolling the handle forward. A small amount of power lever movement prompted the aircraft from rest to the desired speed, which was then controlled by having one lever at ground-idle and one with some reverse thrust selected. The power levers are moved from ground-idle to reverse by lifting a small latch on the forward edge of the stem, just below the knob. The left engine is used for reverse to ensure that no exhaust gases enter the APU-powered cabin conditioning system.
The electrically controlled, hydraulically powered nosewheel steering was notably good, easy to accustom to and with no tendency to oversteer. The carbon-disc wheel brakes were smooth to apply and powerful in their response. The brake and anti-skid system has dual integrated electronic controls with autobrake capability. Emergency brake application is via the parking brake handle, which requires gentle application when being checked at taxiing speeds. The emergency brakes are powerful and do not have anti-skid protection.
The elevation of Wichita's Mid Continent Airport is about 1,400ft, the air temperature was +31°C and there was an easterly wind at 10kt. Runway 19R was used. Aircraft weight for take-off was 32,000kg (70,600lb), against a maximum of 42,415kg. With 8° of flap, the reference speeds were: V1/Vr 107kt, V2 121kt and Vfto (V1 for flexible take-off) 156kt.
The nosewheel steering tiller can be disregarded for take-off. Limited-authority nosewheel steering via the rudder pedals is provided for directional control on the runway during take-off, a rejected take-off, and landing. The power levers, meanwhile, are moved to the forward end of their quadrant, after which the FADEC regulates the power demanded. The engines were slow to spool up initially, but then accelerated rapidly to full power. Aircraft acceleration was, in consequence, slow at first, then increasingly and impressively rapid.
CONTROL FORCES
The control forces required to rotate were light and the aircraft was easily established at about 12° nose-up pitch for the climb. The undercarriage and flaps were retracted without discernable trim change, but then the rapid acceleration to the 250kt climb speed necessitated a prolonged and quite heavy push on the control yoke to maintain the pitch attitude. A large amount of nose-down trim was needed, but the pitch trim (via a two-pole switch on the control yoke) was rapid and effective.
G-FBGX's dual autopilot system is not to production standard, so the aircraft was flown manually throughout our flight. The primary flying controls are mechanically controlled and hydraulically operated. Control in pitch is via separate elevators (to allow one control surface to operate if one elevator becomes jammed), and longitudinal trim is via the variable incidence tailplane.
Roll control uses ailerons, assisted by multi-function spoilers. An aileron jam would be countered by use of the spoilers.
It soon becomes evident that the Global Express has extremely pleasant handling qualities. The aileron break-out forces were light and the blending of aileron and spoiler operation seamless. The controls were well harmonised in all three axes, and the artificial feel was good. Trimming the aircraft to fly hands-off was not easy at first, mainly because the slightest amount of yaw tended to induce some roll. Roll control was extremely powerful, giving exceptional roll acceleration and rates. This was a pilot's delight to experience, but might not be viewed so enthusiastically by passengers subjected to exuberant aircraft handling.
The Global Express remained a pleasure to manoeuvre at 45,000ft (51,000ft is the maximum altitude). In 45° banked turns at Mach 0.8, buffet could be provoked at 1.5g. This was a crisp and readily identifiable buffet, immediately eliminated by releasing back-pressure on the control column. Acceleration to M0.88 and a pull to 1.4g produced no Mach buffet (maximum operating Mach number is 0.9).
Deploying the speedbrakes to FULL at M0.85 (the spoilers perform the function of airbrakes) produced insignificant pitch change and slight burble. In the subsequent descent, with power at flight-idle and speed at M0.75, the airbrakes were extended to MAX (a latched position beyond FULL, intended for emergency descents). A marked nose-up pitch resulted, but this was easily trimmed. The established rate of descent at M0.75 and 40,000ft was a remarkable 8,000ft/min (41m/s).
Upon descent to 14,500ft, the aircraft was stalled. There is a stick-shaker and a stick-pusher. For the clean stall, the aircraft was trimmed at 158kt before reducing speed at 1g by 1kt/s to the stall warning (stick-shaker) at 126kt and stick push at 119kt (the minimum speed seen was 115kt). With the undercarriage down and flaps at 30°, the trim speed was 119kt, the shaker operated at 96kt and the stick pusher at 89kt. In both cases, roll control remained effective down to the stick push and handling characteristics were good throughout, with no tendency for a wing to drop or the nose to slice. At each stick push there was an audio warning and the legend STALL appeared on the flight director.
The effect of configuration changes on trim was investigated next. The Global Express has three trailing-edge flap panels and four leading-edge slat panels per side. Each set of panels employs a central electrical power-drive unit, which drives the surface activators via rigid shafts. Asymmetry protection is built in. The slats can be selected out without flap (via the first detent on the flap selector) and remain out when 6°, 16° or 30° of flap is set.
BENIGN BEHAVIOUR
The aircraft was decelerated, and slats and each flap position were sequentially selected, with the undercarriage being selected down with the flaps at 6°. In each case there was no significant pitch change or ballooning - making the aircraft benign to fly during configuration changes.
At 14,000ft and 250kt rudder deflection was initiated by a rudder pedal "doublet". With the yaw damper operating, the aircraft recovered in one and a half cycles. With the yaw damper switched off, it recovered in about four cycles - indicating that the aircraft does not have a strong Dutch-roll mode. It does, however, have a very powerful rudder with low break-out force, my first doublet causing a greater disturbance than I had intended. (Available rudder deflection is automatically reduced with increasing airspeed).
In the descent to 10,000ft, the left engine power lever was moved to flight idle to allow 5min cooling of the engine before it was shut down at 10,500ft altitude. The aircraft was established at V2, flaps at 6°, undercarriage up and with take-off power on the right engine when Tylski shut down the left.
Because of the desirability of cooling the engine before a routine shutdown, it was not possible to experience a dynamic V2 shutdown. The aircraft was nonetheless easy and pleasant to control throughout, the V2 climb being readily maintained, wings level, keeping straight with rudder using only moderate foot forces which were easily trimmed - all of which indicated that the Global Express would be easily controlled during an actual engine failure after V1. Single engine rolls from 45° to 45° of bank were then confidently flown, the aircraft being reassuringly easy to control throughout.
The left engine was then re-lit using the bleed-air-assisted airborne restart procedure from the checklist. The process was straightforward and painless, and the engine was maintained at flight idle for 5min before being returned to use.
Because of the need to keep the engine at flight idle for 5min I elected to fly a simulated single-engine approach to the instrument landing system on runway 19R at Wichita. The all-up weight was by now 29,360kg, and the threshold speed (Vref) for that weight is 117kt - 5kt is routinely added to this, giving an asymmetric threshold speed of 122kt.
Each pilot has the primary flying display (PFD) on the outboard screen and the multifunction display (MFD) on the inboard screen. The PFD has the attitude and direction indicator in the top half of the screen, with an airspeed ribbon to its left and a vertical altitude scale to its right. The lower half of the screen has the horizontal situation indicator and vertical speed indicator. The MFD has a horizontal navigation display including projected track and waypoints. Traffic alert and collision avoidance system information is superimposed upon this navigation display. The lower third of the screen is used for a vertical navigation display.
These displays provide strong situational awareness cues. They also present much other information (for example, true airspeed, ground speed and flight director modes), so that it takes considerable time to become familiar with the layout and to know instantly where to seek particular information within the presentation.
Flying the simulated single-engined approach to a touch-and-go landing was a delight, requiring a conscious effort to maintain awareness that only one engine was in use. Landing the Global Express was straightforward, power being reduced to idle at the point of the flare and the attitude changed by only a couple of degrees through gentle back-pressure on the control column. The aircraft settled positively onto the runway and the nosewheel was readily lowered with elevator. The prevailing crosswind caused no difficulties.
From this touch and go, both power levers were advanced to the take-off position and the aircraft climbed into the circuit, 1,500ft above the airfield. Once again, the need to push forward and trim to maintain pitch attitude as the aircraft accelerates in the climb was very evident. As Tylski pointed out, pilots would soon adapt to trimming almost subconsciously, and he is right - but it is still a slightly disappointing characteristic because the Global Express has, overall, such thoroughbred handling qualities.
The visual circuit and final landing were as much fun as the rest of the flight, reverse thrust being easy to select after touchdown and noticeably effective before it self-cancelled at about 60kt. The wheel brakes were powerful and effective and the runway centreline was easily maintained with nosewheel steering controlled through the rudder pedals.
The Global Express makes you want to fly it more and know it better. The landing qualities qualify it for the accolade of a "pilot's aeroplane". The automated systems make it efficient and safe to operate. The levels of comfort boasted by Bombardier for its cabin are matched by the efficiency of its cockpit - a working environment equipped to facilitate good crew management and situational awareness.
Source: Flight International
