Bred For 6X?

The new aircraft is an impressively swift pivot for Dassault, which only took its final decision to cancel the 5X programme in mid-December 2017 following engine delays with its much-vaunted Snecma Silvercrest engines, and after numerous order cancellations. Clearly, the manufacturer has been working on a Plan B — now the 6X, which is largely derived from the 5X with a few improvements — for quite some time.

“We wanted to further push the boundaries with this new aircraft, to provide the best flight experience possible using today’s aviation know-how,” Dassault Aviation chairman and chief executive officer Eric Trappier explains. “The Falcon 6X will offer a mix of range, comfort and capability no other large cabin business jet can match while guaranteeing fully mature systems and a proven powerplant.”

‘We wanted to further push the boundaries with this new aircraft.’

The 6X sits in a range gap between the larger tri-jet family members, the Falcon 7X and 8X, and the smaller Falcon 900LX. The 8X can stretch to 6,450nm, the 7X to 5,950nm, but the 900LX only to 4,750nm.

From Sydney, the 6X’s 5,500nm range opens up a 500nm swath of the eastern Indian subcontinent and central/northern China. From Perth, it means nonstops to the Gulf and a large amount of eastern Africa, as well as substantial penetration into central Asia.

After cancellation of the 5X late last year as the result of extensive problems with the Snecma Silvercrest SC-1D engines, Dassault’s successor aircraft is powered by Pratt & Whitney Canada PW812D gearless turbofans, also larger and more capable than the 5X’s Snecmas. The same engine family also powers the Gulfstream G500 and G600 jets.

The Pratt engines’ size — and weight — are driving most of the changes from the 5X to the 6X, including a fuselage stretch of just under half a metre forwards of the wing for weight and balance reasons. In addition to the engines, a new nacelle design has been required to attach them to the rear of the aircraft. Local structure reinforcement has been kept to a minimum, Dassault says, and has largely been limited to the wing and rear fuselage.

Additional fuel tanks fore and aft of the wing, and increased fuel capacity within the wings, enable a range boost to the aircraft, while the slightly larger jet means that the 6X’s vertical stabiliser also needs increased rudder deflection.

The 6X’s performance mantra has changed from the 5X’s bleeding-edge supplier-airframer innovation, where the Silvercrest was both Snecma’s first launch engine and Dassault’s first time launching an engine on one of its aircraft, to tried-and-tested technology.

“The 6X is largely based on the Falcon 5X aerodynamics and system features which were validated during the 5X preliminary flight test program,” Dassault explains. “It has been optimised to take advantage of the new engine, offering a greater range and a longer cabin.”

Like the 5X, the cabin is 1.98m (six feet, six inches) high, and your 1.90m journalist previously confirmed the size and spaciousness difference compared with other fuselage cross-sections in Dassault’s cabin mockups for the 5X. With a 2.58m wide cabin, Dassault manages to accommodate a standard load of sixteen passengers (with up to nineteen in total) in three separate lounge areas.

“The industry has been moving towards ever wider and higher interiors, and customers told us what they wanted most in our new Falcons was more space. So we designed the Falcon 6X from the cabin out, making it as passenger-centric as we could while still delivering the high performance and other flying qualities that customers value in Falcons,” Eric Trappier notes.

Twenty-nine large windows bring light into the cabin, as does the unique galley skylight, which is both a first in business aviation and also inherited from the 5X. This seeming oxymoron is a complexity that, to an extent, the 6X, which presents a number of Dassault innovations on the 5X that never made it past the preliminary flight testing.

More than just a 5X update

The 6X stretches 25.68m long, 48cm longer than the 5X, and maintains the 25.9m wingspan and 7.5m height to the tip of its vertical stabiliser. Empty, it weighs 20,830kg compared with the 5X’s 18,144kg, with a maximum takeoff weight of 35,135kg (to the 5X’s 31,570kg) and maximum landing weight of 30,025kg (compared with 29,980kg).

“The Falcon 6X is able to land with much more fuel than competing aircraft. This allows operators to make a short hop to an interim airport, pick up passengers, and then continue on to an overseas destination without having to refuel,” Dassault notes, giving a mission example of Washington, DC to New York (just under 200nm) and then on across the Atlantic to London or Geneva (3000-3300nm). “That’s mission flexibility with economic efficiency.”

At sea level and MTOW, its balanced field takeoff distance requirement is 1,670m, while it requires just 760m to land. In the air, the jet is certified to 51,000 feet or 15,545m, and its cabin is pressurised to 3,900 feet (1,189m).

“With extendable leading-edge slats and trailing-edge flaps on the wings, approach speed can be as low as 109 kias (202 km/h),” Dassault says, using the NBAA’s IFR reserves and carrying eight passengers, three crew, approach up to six degrees and at sea level. Dassault highlights that the jet is designed to be capable of serving challenging airports at London City, Lugano, Saint Tropez and Aspen, among others.

The 6X features Dassault’s innovative flaperon, an “active high speed deflection control surface” developed from the Rafale fighter and serving multiple functions: either a flap, an aileron, or a differential surface to supplement lift coefficient. Dassault expects the flaperons to be especially welcome during approaches with a steep approach file, enabling pilots to increase drag while ensuring a high lift coefficient.

The wing is, however, largely unchanged from the 5X.

Big engines are big news

Pratt & Whitney Canada’s PW812D is part of the wider PurePower PW800 series, sharing a common core technology with more than a dozen other PurePower engines seen on business jets in its 10-20,000 pound thrust class and, indeed, larger airliners in its Geared Turbofan version, although the PW800 is not itself geared. It offers a bypass ratio of 4.5-5.0, fan diameter of 44in (112cm) and a noise target of 15EPNdB below Stage 4.

“The whole PW800 family was launched about 15 years ago on the PW810 for what was, at the time, [the Cessna Citation] Columbus. We’ve been working at both the lower and top end of the family for quite some time,” Pratt & Whitney Canada senior vice president Maria Della Posta tells Australian Aviation. “We’ve demonstrated three cores: small, medium and large, let’s call it that. We have different levels of flight testing and demo testing for all three of them. All told, it’s about 20,000 hours.”

Those twenty thousand hours, Della Posta says, are “a combination of inflight and ground testing. All the performance indicators exceed the original guidelines, and that’s in terms of thrust — for this engine that’s around 13,000 pounds — fuel consumption and all the parameters that have been flown and demonstrated.”

Della Posta counts the PW812D (D for Dassault, the airframer explains) as one of the “small” cores, for which “we’ve done just under a thousand hours in terms of testing”. Several thousand hours are left, with Della Posta conjecturing that this is in the “high single” thousand hours total, much of which will be combined with Dassault’s flight testing programme.

With the tight timescales for production and testing of the Falcon 6X, Della Posta estimates that “we will have engines to them in the next 18 to 24 months. It’s very front loaded. Because we’ve already been working on the PW800 as a family, we’ve done a lot of ground testing ourselves.”

As regards hot and high testing, Della Posta says that she doesn’t expect any particular challenges for the smaller turbofan, noting that the testing has already been completed for the PW814 and -815, which power the Gulfstream G500 and G600 in their -GA models, respectively.

Evolution and a little bit of revolution in the flight deck

Dassault promises that “the cockpit of the new Falcon 6X will both delight pilots and improve situational awareness,” and indeed the FalconEye combined vision system selected by most customers of the larger Falcon 8X will be a standard product on the 6X. FalconEye blends live thermal and low-light camera imagery from six sensors (four day, one night, one thermal) embedded in the nose of the aircraft with synthetic terrain database images into a single view, displaying it on the 1280 x 1024 pixel resolution head-up display, which offers a 30-40 degree field of view.

‘FalconEye blends live thermal and low-light camera imagery.’

Dassault offers the HUD as a single or dual configuration, but expects a significant proportion of its customers to take the dual version to ensure that both left-seat and right-seat pilots are familiar with its operation.

Within the flight deck, the 6X is a full fly-by-wire aircraft, and inherits the wider flight deck and airliner style displays from the 5X it replaces, including the Honeywell EASy III avionics suite. Dassault has integrated its FalconSphere II electronic flight bags into the console, with the intent being to leave the EFBs themselves semi-embedded in the console but allow them to synchronise wirelessly with pilots’ own tablets or other devices for live or semi-live updates.

The 6X offers a unique digital flight control system, offering reduced pilot workload with full auto trim on three axes, a trajectory based control system with path-stable closed loop automation, and high authority on all flight control surfaces — primary and secondary — providing safe flight envelope protection, Dassault notes. In addition, the aircraft is compliant with the various new generations of air traffic management requirements.

“Because of the delays in the 5X, the 6X programme has stayed very conservative, and they’re using basically the suite that they know works and continues working in the 8X. When you look at the 8X’s EASy III, that’s basically what’s going in the 6X,” Dr Woody Saland, director of pilot experience and new flightdeck technologies at the company’s US operation, Dassault Falcon Jet, tells Australian Aviation. “I think it’s the logical flight deck.”

Suggesting what would be a very unusual move for an airframer, Saland suggests that “it would be terrific if [Dassault] manufactured the avionics themselves, because they could control their future, but you’re limited to Honeywell, Rockwell Collins, maybe Thales. They’ve had now fifteen, eighteen years of developing the EASy flight deck with Honeywell, so it was something that all the Falcons are using.”

“The new ground is in the fly-by-wire over the 8X, but not the avionics,” Saland explains, noting that there is sufficient difference to require a separate type rating. “Across the members of the family, the problem is that we have three-engined airplanes and two-engined airplanes, and right now they’re all different type rating. This will be a new type rating. The problem is that you’re going from an 8X three-engine fly-by-wire to a two-engine fly-by-wire.”

“For the pilot it’ll be a very easy transition because the flight deck is the same, but for the authorities it’s probably a full type rating,” Saland says, although he notes that private jet owners and operators are keen to reduce the amount of conversion time. “There’s pressure, but I don’t think it’s practical. In a one-month initial [type rating session] you’re only in the classroom ten days, twelve days, and that’s really not a lot of time to go over every single system.”

“If you’re in the air force, if you learned a totally new airplane it would be in months: six months, maybe, to learn all the systems,” Saland explains. “In business jets, because of the cost, and because of taking people out of the loop and sticking them in the classroom, we try to do it in a month. It’s very short to learn what’s really happening. I don’t see that being any longer, because of the economic constraints, but I think it’s not a lot of time to learn a brand new airplane.”

The flight deck is also integrated into the FalconScan connected aircraft system, including real-time diagnosis options via FalconBroadcast, automatic maintenance reports synchronised with the electronic logbook and flight bag, a centralised aircraft system software upload on the ground, information security protection of maintenance activity data, and a remote control functionality offered by the Dassault Tech Centre that also contains playback capabilities.

FalconScan is directly connected to every system of the aircraft through a dedicated high-speed data bus, collecting, processing and storing what Dassault calls “all relevant data” with a capacity of up to 100,000 parameters in real time. The system also provides dynamic access to the maintenance manual, aircraft wiring diagrams, and aircraft-specific maintenance including activity reports, service bulletin status, and other comments.

FalconScan is, Dassault says, ready for next-generation health and trend monitoring programmes including prognostic algorithm integration and big data advanced services.

On the systems side, Dassault is keen to highlight the lessons it learned from the Falcon 8X and during the 5X test campaign, and is labelling the Falcon’s “dispatch oriented design” as a “practical balance between proven technologies and innovations”. With additional system automation, and a full range of certified electronic checklists that include normal, abnormal and emergency procedures, Dassault hopes to improve both reliability and user experience for operators.

On the ground, improved aircraft initialisation with a smart power system that configures itself depending on the power sources available means a shorter startup time, and the battery system has been optimised to improve cold weather performance, including with heaters. An engine oil replenishing system is an option on the aircraft, while Dassault also expects the patented algorithms contained in the latest version of its FalconScan maintenance system to bring benefits: integrated testability, inflight and ground health monitoring, troubleshooting assistance adapted to every tail number, and a readiness to integrate with future systems currently under development.

Dassault expects first flight of the 6X in early 2021, with certification and entry into service in 2022: a tight timescale, although Dassault will be able to build on testing from the 5X programme.

For Dassault, the 6X offers a chance to redeem itself from backing the wrong pair of horses attached to the back of the 5X, and to fill the missing gap in the Falcon family.