Bombardier’s Global line of ultra-long-range large-cabin business jets was launched in the 1990s with the Global Express. At the time of its certification in 1998, this had the largest cabin of any purpose-built business jet, a distinction it held until Gulfstream delivered its first G650 in 2012.
Bombardier answered with the Global 7000, a clean-sheet design that had a cabin 3.41m (11ft) longer than the Global 6000’s, shooting for a 2016 certification date. However, this schedule was pushed back to 2018 when technological advances allowed the Canadian airframer to field an even more capable aircraft. The revised design promised a range in excess of 7,500nm (13,900km), and was renamed the Global 7500.
Once a sizeable force in several sectors as an aircraft manufacturer, Bombardier now only competes in the business jet sector with its Challenger, Global and Learjet product lines. It was against this backdrop that Flight International was invited to see how Bombardier’s newest and largest offering competes at the pinnacle of that sector.
FRONT-TO-BACK EVOLUTION
The Global 7500 is a true globe-spanning time-space machine. Two notable technological changes from its older stablemates are its new wing and the incorporation of a fly-by-wire (FBW) flight control system.
Bombardier has made the most of the cabin expansion, offering the longest bespoke business jet cabin, with four large living spaces. Gulfstream’s rival G650 can offer four living areas, but only if there is no crew seat area. While the 7500 shares a common fuselage cross section with the Global 6000, it is a totally new design, with thinner structural frames. The result is a 2.5cm (1in) increase in interior height and width. The new design also allows for dramatically larger 58.4cm-high cabin windows, fully 80% larger than the 6000’s. The new fuselage design has also allowed the company to optimise window location, with each living space having three per side that nicely illuminate the space.
The Global 7500’s almost 16.6m-long cabin is divided into these four living spaces, plus a forward crew rest area and long-range galley. The forward entry door opens into the galley area. Designed for meal preparation with heavy passenger loads on long-range flights, it has both microwave/convection and steam/convection ovens.
Aft of the kitchen, as Bombardier refers to it, is a crew rest area and forward lavatory. Bunk beds are an option for the crew rest area, and will allow two crew members to sleep as the Global 7500 spans the globe. Placement of the forward lavatory outside the cabin’s main living spaces offers greater privacy.
The four living areas occupy the aft 11.0m of the cabin. From nose to tail they are: club, conference, entertainment and master suite with en suite lavatory. The living areas are fitted with Bombardier’s bespoke Nuage seats. A patented articulation scheme allows for a deep recline that provides a near berth-like level of comfort. Living area amenities are controlled by an obligatory app for personal devices. Additionally there are bulkhead-mounted suite controllers for each area. Finally there are handy side console-mounted pop-up “touch dials” to control cabin functions. These have a nicely weighted feel to them, and even non-tech savvy passengers will be the masters of their cabin experience.
As expected for a jet at this price point, customisation options are nearly endless. I did not go into the maths, but Bombardier says there are over 10,000 floor plan permutations. Highlights include a three-person divan that pulls out into a bed, and a real bed in the master suite. The en suite bathroom can even be ordered with a stand-up shower.
Regardless of the permutation selected, there are several features that all cabins share. The 0.7bar (10.3psi) delta p pressurisation system maintains a 4,500ft cabin altitude up to 45,0000ft, rising to 5,670ft at its operating ceiling of 51,000ft. Further enhancing the cabin environment is a particulate HEPA filtration system of 99.97% claimed efficiency and an activated carbon gas phase filtration system that removes odours and volatile organic compounds. Some cabin air is recycled, increasing environmental system efficiency as well as increasing cabin humidity levels.
In each living area the L’Opera sound system’s sweet spot can be adjusted to a specific seat. Finally there is Bombardier’s innovative Soleil lighting system, which uses flight management information to develop a custom lighting profile designed to synchronise passengers’ circadian rhythms with the time at their destination.
VISION FLIGHTDECK
While for passengers and owners the Global 7500’s most notable traits are its ultra-long range and large cabin, for pilots it will undoubtedly be the cockpit and FBW control system. The type’s Vision flightdeck is a state-of-the-art working environment for long-haul business jet pilots. Overall the cockpit is well arranged, with the flight control sidestick controllers mounted on the outboard sidewall console. The Collins Aerospace Pro Line Fusion avionics system features four large (15.1in) active matrix liquid crystal display adaptive displays. The sidestick’s location makes for unencumbered viewing of the large display areas.
The Global 7500 also comes standard with a Collins head-up display (HUD), which acts as a primary flight display as well as the primary display for the enhanced vision system (EVS). The EVS is fed by one optical and two infrared cameras. The system will display the increasingly common LED runway lights. As has become the norm, the Vision flightdeck’s primary flight display and HUD have a synthetic vision system capability. The intuitive roller ball cursor control devices are located outboard of the thrust levers, while there are two multifunction keyboard panels on the centre pedestal. From a subjective standpoint I found the Global 7500’s flightdeck on par with the G650’s PlaneView II.
FBW CONTROLS
When the Global Express was announced in the 1990s, Bombardier was exploring the possibility of launching it with a FBW flight control system. For a number of reasons, as reported at the time by Flight International, in the end it fielded the jet with a conventional flight control system. FBW control development is a large task, with Bombardier’s first primary FBW control surface application being the rudder on the CRJ1000 regional jet.
The company’s first full FBW-control aircraft was the CSeries (now the Airbus A220), which was certificated in 2015. I flew the longer CS300 variant in 2016 and was quite impressed by the aircraft’s handling qualities. While Bombardier subsequently transferred the CSeries programme to Airbus, it kept its FBW technology. Leveraging resources and technology developed for the CSeries, the Global 7500’s flight controls are based largely on that system. Overall system architecture is the same: a conventional hydraulic system activated by electrical units controlled by triple-redundant primary flight control computers. Additionally, like the CSeries, the Global 7500’s system has a back-up alternative flight control computer and a ram air turbine to provide auxiliary hydraulic power to the controls.
Each manufacturer tailors the control system to fit its needs and ethos. As I have proposed in previous flight reviews there are four areas of differentiation: pitch axis control scheme, lateral-directional control scheme, envelope protections/limitations, and engine-out response. As I wrote in depth in my 2016 CSeries flight review, Bombardier uses a C*U pitch control scheme. This blends pitch rate with g command while providing artificial speed stability. Conventional aircraft have speed stability, providing tactile feedback that enhances situational awareness. This pilot prefers aircraft that display speed stability, a trait found in many manufacturers’ FBW-controlled aircraft.
In roll, Bombardier has selected a roll rate command solution, the seeming industry standard when up and away (in clean configuration). At full sidestick deflection the aircraft will roll at 20°/s, decreasing to 10°/s as angle of attack increases to its limit. In yaw the pedals command rudder deflection, which is limited based on speed and configuration. This is in essence the same as a conventional flight control aircraft. Finally, in a conventional flight control aircraft the lateral and directional axes are coupled: yaw and roll motion causing a corresponding response in the other axis. FBW schemes can keep this interplay, moderate it or delete it altogether. The Global 7500’s FBW scheme keeps them connected, allowing the pilot to roll the aircraft with the rudder pedals.
FBW PROTECTIONS
The overall benefits of a FBW control scheme are well documented, allowing for reduced structural weights as well as increasing performance in some areas. The ability to incorporate envelope protection features is an area where FBW control systems can outshine conventional ones. It should come as no surprise that each manufacturer has its own philosophy on envelope protections. In general terms the Airbus FBW scheme has the most strident envelope protection features, with Boeing’s offering less. Bombardier’s level of FBW protections falls between those of the two major airframers. In pitch the Global has both high- and low-speed protections, as well as g protections.
Unique to Bombardier’s system is that its sidestick has soft and hard deflection limits in pitch. Stick displacement up to the soft stop keeps the aircraft in the operational envelope, preventing angle of attack and g exceedances. Pulling through the soft stop to the hard stop requires an additional 4.5kg (10lb) of force. The extra pull/push will generate maximum available aircraft performance without regard to structural limitations. Aircraft pitch attitude is limited to 30° nose up and 20° nose down. In roll the Global is limited to a maximum of 80° angle of bank.
The final area that warrants further discussion is how the aircraft responds to an engine failure. Such a failure on a multi-engined aircraft presents the pilot with two problems: one is the immediate degradation of performance, and the other a controllability issue (centreline thrust excepted). Performance loss is mitigated by proper loading of the aircraft to ensure it can fly after loss of an engine. Control of a conventionally controlled aircraft after an engine failure on take-off requires immediate pilot response to prevent disaster. Let that sink in for a moment.
This is industry standard, and has been since multi-engined aircraft were fielded. Certification authorities have accepted this risk, as in the past any technological solutions were likely to be too complicated and/or unreliable. But FBW control technology has changed that. Control schemes can be implemented that will reduce or totally eliminate the yaw and roll associated with an engine failure. Of the FBW aircraft I have flown, Boeing’s scheme on the 777/787 is the most proactive in controlling yaw and roll, allowing an engine failure event to be flown with feet on the floor. Gulfstream’s FBW system on the G650, an aircraft that I found a joy to fly, is towards the other end of the spectrum, taking no specific actions to mitigate the yaw and bank angles.
Airbus and Embraer FBW schemes fall in the middle, limiting how much yaw and bank can develop. Bombardier’s system does have an “in-flight partial engine out compensation feature” designed to limit aircraft roll and yaw response to an engine failure. Based on my limited experiences with them, Bombardier’s scheme allows less yaw and roll to develop than Gulfstream’s, but more than on Airbus or Embraer types.
PASSPORT TO SUCCESS
After this thorough review of the Global 7500’s salient features, it was time for me to take sidestick in hand and experience how Bombardier’s (and the industry’s) largest and longest-range business jet performs. Our preview flight was flown out of Norman Y Mineta San Jose International airport in California. The preview aircraft, N750GX (serial number 70006), was a production example with a fully fitted interior.
I followed demonstration pilot Bruce Duggan as he conducted the pre-flight walkaround inspection. Globals are large, distinctive aircraft, but the 7500’s large cabin windows readily differentiate it from its smaller stablemates. With the inspection complete I joined Michael Goggins, Bombardier standards captain, on the flightdeck. After strapping into the left seat I attained the design eye position by reference to the alignment balls on the windscreen’s centre pillar. The sidestick is the same as on the CSeries/A220, with the exception of a few buttons, and fell comfortably to hand after adjusting the forearm rest. Goggins guided me through pre-start flows and flight management system initialisation. The electronic checklist was a smart one, automatically checking off items sensed in the correct position.
The tail-mounted auxiliary power unit (APU) was used to start the GE Aviation Passport engines. The Passport was designed specifically for the Global 7500 and features a large, 1.32m (4ft 4in) single-piece 18-blade titanium blisk. The engine sports an overall pressure ratio of 45:1, on par with the CFM International Leap, and is 8% more efficient than other engines in its class. The powerplant’s efficiency is perhaps the key element to the Global 7500’s range. The starts were FADEC-controlled, dry motoring for an average of 80s to reduce rotor bowing. Rotor bowing due to asymmetric fan blade cooling is a common problem for high-efficiency engines such as these, the Leap or Pratt & Whitney’s geared turbofan family. Total start cycle time for each engine was less than 2min.
Prior to leaving the chocks, the flaps were set to 2, extending both leading edge slats and two-slot trailing-edge Fowler flaps. While found on most airliners, slats make for a complicated wing and are typically found only on larger business jets. For a business/transport aircraft the wing must be optimised for two conditions: cruise and runway performance, high and low speed respectively. These two divergent needs drive wing design and inherent compromises.
Large Gulfstreams have fixed leading edges, so why then did Bombardier fit its Globals with slatted wings? High-lift devices allow the wing to be sized/lofted for optimum cruise performance, without degrading runway performance. The Global 7500 weighs more than both the G650 and G700, yet has a smaller wing than both types. The slatted wing gives the Bombardier model better runway performance (shorter take-off and landing distances) and as a consequence of higher wing loading a better ride in anything less than smooth air.
Taxiing to runway 30R allowed me to get a good feel for the Global’s ground handling, with the tiller-controlled nose wheel steering making negotiation of the several 90° turns a snap.
BRISK TAKE-OFF
Fuel load for the preview flight was only 6,240kg, or about one-quarter of the 23,400kg maximum load. Take-off speeds were correspondingly low: 109kt (200km/h) indicated at V1/VR and 124kt V2 for the 34,100kg Global. Once aligned and cleared for take-off I advanced the thrust levers, with the autothrottles engaging and setting take-off thrust (97.2% N1). Needless to say, the lightweight Global 7500’s time on the runway was short. Sidestick forces in pitch were light as I set an initial pitch attitude of 10° nose up. Once airborne, I tracked flight director guidance for the 200kt climb out of San Jose.
As I had found when flying the CSeries, sidestick forces were minimal during clean-up and acceleration. I hand flew the Global in a climb to the east and accelerated to 300kt for our short climb to 15,000ft. Due to time constraints 15,000ft would be our flight’s maximum altitude, preventing an exploration of the model’s advertised high-speed capability at altitude.
ENVELOPE PROTECTIONS
Level in a medium altitude block (around 15,000ft) I was able to take the Global 7500 to 330kt, just 10kt below its maximum speed (VMO) at that altitude. I did a few sharp control inputs in each control axis, and as could be expected for a FBW aircraft the response was well damped. Had I let the Global accelerate past VMO, the flight controls would have pitched the aircraft up to prevent an overspeed.
Next, I slowed the aircraft to explore its low-speed protection features. The first point was in a gear-up flaps 2 configuration, reflecting climbout on take-off. With the autopilot engaged and autothrottles off, I slowed the Global in level flight. Passing 116k triggered an auditory “speed” warnding. Further slowing to 109kt, “underspeed” was announced while the autothrottles woke up and accelerated the aircraft to 120kt, safely above the stall speed.
The second point was in a landing configuration, gear down and flaps 4. This exercise would simulate a pattern where the pilot over-banked the aircraft with too low a power setting, in an attempt to get to the runway. I set the power to IDLE (autothrottles off) and rolled the Global into a 45° angle-of-bank turn to a simulated final. In a gentle descent at 120kt I pulled aft on the sidestick until I hit the soft stop. At the stop the stick shaker activated and the autothrottles activated to power the Global out of the accelerated stall.
With time constraints dictating a return to base, I cleaned the aircraft up and headed towards a fix on the RAZRR 4 RNAV arrival to Norman Y Mineta San Jose International. I found the pilot interface with Vision flight was fairly intuitive and allowed me to quickly load the RNAV (GPS) Y 30L. I hand flew the approach, following flight director guidance for both lateral and vertical paths. With the flaps set to 4, final approach speed was only 113kt.
The Passport engines were easily modulated to maintain speed in what was a 4° nose-up attitude. At 50ft I retarded the thrust levers to IDLE, approximately the same point I typically retard them in a 737. At 30ft I gently pulled aft on the sidestick to set an 8° nose-up attitude to flare the aircraft. On touchdown, the speed brakes automatically deployed, lifting four panels on each wing, to dump lift. Reverse thrust and moderate wheel braking quickly brought the Global to a safe speed for runway turnoff. During the taxi back to the ramp, Goggins started the APU, its generator coming online when the engines were shut down.
LONGER CABIN AND RANGE
After shutdown I paused and reflected on the Global 7500’s handling qualities. As with the CSeries I had flown in 2016, I found its FBW control system notable in that I did not notice it until the envelope protections kicked in. I appreciated that Bombardier provided artificial speed stability.
The Global’s praiseworthy flight control system, however, rightfully takes a back seat to its long and luxurious passenger cabin. The Global 7500’s range outdistances that of both Gulfstream’s G650ER and still-in-development G700.
Hopefully this review has opened a window into the Global 7500’s capabilities and where it fits in the market. The question of which long-range, large-cabin jet fits the bill may well boil down to windows: oval or rectangular?
Note on flight control certification standards
The reader may question why they have been taken on this brief journey recounting how various manufacturers’ flight control systems cope with an engine failure. The answer is that the systemic acceptance of risk in aircraft certification needs to re-evaluated. The timeline for this proposal is highlighted by the grounding of the Boeing 737 Max. For decades it has been assumed that pilots could effectively intervene to prevent a runaway stabiliser from causing loss of control. Unfortunately, this assumption was proven wrong in two tragic instances. This pilot has gone on record saying that Maneuvering Characteristics Augmentation System failure should not necessarily have led to loss of life. But the question becomes why are systems whose known failure modes require immediate pilot action to prevent loss of life still allowed to be certificated? Fly-by-wire control systems can be deployed such that no pilot intervention is needed to safely recover an aircraft from a critical-moment engine failure. This is not a dig at any manufacturer, rather a query for the industry. -MG
