A Pilot Reviews Dassault's Falcon 6X

Flight test activity on the Falcon 6X fleet has reached the stage where it’s now a matter of proving the jet’s reliability and assuring the cabin features meet the demanding requirements of a $47 million jet.

In the meantime, the 6X has matured to the point where Dassault invited BJT to sample its flying qualities and performance ahead of certification and entry into service early next year. Per the usual process, I traveled to Dassault’s Istres Flight Test Center near Marseille, France, to fly the 6X.

The first step was a briefing with test pilots Bruno Ferry and Tom Valette, and flight test engineer Flora Corsia at Istres. We would be flying the first 6X, serial number 1, the same airplane in which Ferry and Valette flew on March 10, 2021, marking the beginning of the 6X flight test program. As the original prototype, this 6X is not equipped with a production interior and still carries a cabin full of test equipment including water tanks used to quickly adjust weight and balance for various test conditions.

In preparation for that first flight, Ferry, Valette, and other Dassault test pilots spent time learning about the new jet’s systems and operating characteristics in the systems integration test station (SITS) simulator, which is located at Istres. This also was my introduction to the 6X. The SITS doesn’t exactly replicate the 6X as it isn’t a full-motion simulator and it doesn’t have flight control actuators, which the bench test facility at Dassault’s headquarters in Paris does. But the SITS does duplicate the 6X’s systems and avionics, which is now the EASy IV suite based on Honeywell Primus Epic avionics.

Each new Falcon jet improves upon the last, and the 6X is no exception. Now the largest Falcon with the widest and tallest cabin of any purpose-built business jet, the 6X incorporates unique design features that should appeal to owner and pilot alike.

Originally launched as the 5X, the 6X came about after the 5X was canceled because of insurmountable problems during the development of the 5X’s Safran Silvercrest engine. A fuselage stretch matched the airframe to larger engines—Pratt & Whitney PW812Ds—and the result was serendipitous, a longer-range, wide- and large-cabin jet that probably was a better fit for the market shift toward ultra-long-range and large-cabin business jets.

With years of experience designing and manufacturing digital flight control systems in-house, Dassault engineers have maximum flexibility when it comes to expanding its franchise in the large-cabin market. Dassault’s fighter jets were its first aircraft to feature fly-by-wire flight controls, then the Falcon 7X business jet was so equipped, entering service in 2007. The 7X and 8X proved that it is possible to make large Falcon business jets with the pleasant handling characteristics of their conventionally controlled predecessors. The 6X continues that philosophy, but with full digital control of all flight control surfaces. This includes integration of flaperons, giving designers even broader options for fine-tuning the flight controls to optimize performance and handling. Another addition to the 6X’s flight control system is integrated digital control of nosewheel steering, which makes steering on the ground more precise. Flaps in the 6X are now electrically powered, not hydraulically as on previous models.

Systems Changes

Dassault aims to make it easy for pilots to transition between models, and the 6X has just two operating techniques that are different from the 8X, according to Ferry. “For us,” he explained, “it’s important that the family of Falcons, especially for normal procedures, has to be the same.”

But that doesn’t mean that Dassault engineers didn’t take the opportunity when designing the 6X to make it even easier to operate than the 8X.

Preparing for engine start is much faster with a redesigned overhead control panel (OCP) that has many fewer buttons and a dark-cockpit philosophy. A dark button now signifies what Ferry said is called “dark auto,” and this means that the system could be on or off. What each button indicates, according to Ferry, is “not the status of the system, it is the status of the command. In the procedures, when you have to check a specific position of a button, we say: ‘dark auto’ because the system chooses between off or on; and a lighted [button] is on or off depending on the status of the command.”

A maintenance section of the OCP on the rear side is covered. These switches are for maintenance use and certain abnormal or emergency situations. For example, pilots might use a button to assist with engine starts in cold weather but otherwise will keep these switches covered by the opaque cover.

Bringing the 6X to life starts with one switch moved to the “on” position; then, the aircraft runs through an automatic systems initialization process. Once that is done, the APU is started so bleeds can be switched on for engine start. Another 6X change is that both engines are started with one knob; just move the power levers to the idle position, turn the knob to “start,” and first engine 2 starts followed by engine 1, with no pilot action required other than monitoring the engine gauges. “The fewer actions, the better,” said flight test engineer Corsia.

The 6X’s parking brake is a pull-and-turn switch that electrically locks the brakes, with no need to step on the brake pedals. It isn’t used for emergency braking.

With dual FalconEye combined vision system head-up displays, both of the 6X’s sidestick controls have switches to turn on and off HUD imagery.

EASy IV avionics improvements include 2D and 3D airport moving maps, ADS-B In display of airborne and surface traffic, SiriusXM weather, and runway overrun awareness and alerting system.

The 6X’s takeoff/go-around button is moved to a more accessible location on the center side of the power levers instead of on the back of the levers like in the 8X. “This one is more natural when you want to go around,” said Ferry.

There are two mechanical stops for the power levers: idle (protected by two toggle levers that must be pushed to move the power levers all the way back to shut the engines off) and takeoff. Just aft of the takeoff stop is a soft detent for the maximum climb power setting. After the 6X enters service, Dassault plans to make that soft detent flexible, so the max climb setting can be adjusted for varying conditions such as aircraft weight and outside air temperature.

Electrical Improvements

Breaking new ground in Falcon design, the 6X’s electrical system is an AC-based design, unlike previous models’ DC heritage. Two transformer-rectifier units (TRUs) and one standby TRU provide DC power. “In the 6X,” Ferry said, “we’ve got some DC busses and AC busses. It’s more complicated for the crew to configure or reconfigure the systems, so in this aircraft, in maybe 95 percent of the failures the reconfiguration is completely automatic.”

Both 40 Ah main-ship sealed lead-acid batteries are mounted behind an access panel on the aft right fuselage near the right engine; they are much easier to service or remove during cold overnights than the 8X’s battery, which is located inside the aft fuselage maintenance area.

A ram-air turbine (RAT) provides backup power in case of engine- and APU-driven generator failure, and it deploys automatically or manually if necessary.

Modifying and simplifying the 6X’s hydraulic system was a key goal and gives pilots a more automatic backup system with greater redundancy. “There is a huge difference between the 6X and 8X,” said Ferry. There are two electrically driven hydraulic power packs (HPP), one for each hydraulic circuit, he explained. “It’s a system which gives some robustness to the most principal [control] surfaces of the aircraft in case of hydraulic failure.”

Each engine has two hydraulic pumps, both of which run their hydraulic circuit. HPP A provides a backup to operate the rudder and right-hand elevator and HPP B feeds the left- and right-hand ailerons.

There are three scenarios where one or both of the HPPs will activate automatically. First, if an engine quits at high altitude, HPP A will switch on. At lower altitudes in the airport environment, the loss of one engine will cause both HPPs to activate, or both will also run with complete loss of one hydraulic system (essentially the same as an engine out). The third scenario is loss of one hydraulic pump; in this case, that hydraulic circuit’s HPP will automatically switch on. As another backup, the pilot can force HPP A or B to switch on and provide hydraulic power for the applicable failed circuit. “It’s completely automatic,” Ferry said, “and it isolates [the HPP] part of the circuit from the main circuit.”

In the unlikely event of dual engine failure, there isn’t enough electrical power, even from the RAT, to power an HPP, so a backup hydraulic pump—powered by the RAT or the main-ship batteries—is available to enable continued flight. The backup pump switches on automatically and is tested after each flight to ensure automatic power-on upon engine shutdown.

“It's like getting ready for whatever next failure can come around and making sure that those controls will always be fed,” said Corsia. “It’s an additional feature to the standard hydraulic system from the 8X.”

Air systems on the 6X don’t share the backup environmental control system pack that is on the 8X but feature a precooler in the engine masts to regulate air temperature in case of a pack failure. A ram air scoop has a heater to warm outside air in a pack failure situation when flying in cold temperatures.

Wing anti-icing on the 6X can be set to pre-warm the wing leading edges while taxiing. And during takeoff, pilots can set wing anti-icing in the armed position so that it runs until full power is selected, and then it is switched off. Once power is retarded after takeoff, anti-icing automatically switches back on, eliminating another pilot action, unlike on the 8X where taking off with wing anti-icing on is prohibited and pilots have to manually switch it on after takeoff.

The 6X carries 33,790 pounds of fuel, giving it a maximum range of 5,500 nautical miles at Mach .80 carrying eight passengers and three crew. At Mach .85, the range drops to 5,100 nautical miles. The maximum speed is Mach .90. The 6X fuel system adds two auxiliary tanks, a 3,000-pound center section, and an aft fuselage tank holding 1,200 pounds, both of which serve the two engines. Fuel balancing is simply a matter of selecting “transfer” on the fuel system synoptic. The fuselage tanks feature fuel inerting via an onboard inert gas-generating system.

A new landing gear feature is a brake heater, which is switched on after gear retraction and during the initial descent to clear any frozen water. When the parking brake is set, it automatically is switched to a higher pressure when the power is advanced from idle. Because the 6X’s parking brake is electric, it can’t be used for emergency braking as on the 8X, so an alternate braking switch is available. This provides half the hydraulic braking pressure but no anti-skid, so pilots have to avoid deceleration of more than -1.5 g or the wheels will lock. The PFD and HUD provide the deceleration indication, just below the speed scale. Autobrakes will be certified after entry into service.

Pilots flying in the U.S., where mandatory oxygen mask use is required above certain altitudes, will appreciate the oxygen saver feature. This allows one pilot to wear a mask but breathe normal air, and if a depressurization happens, the mask automatically switches on the oxygen. This is also available on the 8X.

Flight Controls

Perhaps the most significant new feature in the 6X is the flight control system, which incorporates a flaperon (flaps that double as ailerons) on each wing, eliminating the spoilers used on the 8X and 7X. The flaperons move in the same direction as ailerons to enhance roll control. “It’s very precise,” said Ferry. “All the pilots say that it’s a huge difference between the 8X and the 6X.”

Flaps are electrically actuated on the 6X, not hydraulically as on previous Falcon models.

Four airbrakes (two on each wing) increase drag, but only at the maximum setting AB-2. In the AB-1 setting, flaperons move down to increase drag. This configuration reduces vibration for both airbrake settings, to a significant degree compared with the spoiler-equipped 8X.

During landing, all the surfaces—ailerons, flaperons, and airbrakes—move up to kill lift once weight is on wheels. This is automatic, even with the airbrake control in the AB-0 position.

Roll control is still fully available because the opposite side aileron can move down. “Because the airbrake position for aileron/flaperon is like a new reference or new zero [point],” Corsia said, “and if you control through all the roll, it will come off the new zero position.” While this all sounds complicated, she acknowledged, “It’s easy to use.”

Flaperons serve one more purpose, and that is aiding in pitch control in case of an elevator control failure.

Flying a steep approach will be slightly different in the 6X. For airports like London City with its 5.5-degree path, pilots will use the AB-1 setting at Vref. This increases drag but doesn’t change the angle-of-attack (AOA) so the view from the flight deck will look like a normal landing, according to Ferry. For 6 degrees or steeper—for example, Lugano in Switzerland at 6.65 degrees—AB-2 will be required at Vref +5. This is because above 6 degrees at AB-1 or AB-0, the 6X would accelerate, he said, “even if you are in the landing configuration.” Steep approaches will be certified for the 6X after it enters service.

For 6X pilots, Ferry said, “The aircraft is very easy to land. You’ve got sufficient precision of the touchdown.” Airfield performance is close to that of the 8X, but the new flight-control system results in much smoother touchdowns, a “kiss landing” every time, he said.

Flying the 6X

The day before I flew the 6X, Ferry and I replicated our planned mission in the SITS to get me familiar with the systems and the new EASy IV flight deck. The SITS doesn’t replicate the control feel, but it was helpful to spend some time learning what to look for and the processes involved in operating the 6X.

We went through the start-up procedure and then some of the profiles and maneuvers that I would be flying in the real 6X, including a climb to FL400, shallow and steep banks, descent with various airbrake settings, slow flight at Vmin, a sidestep on final approach, go-around, and a normal landing. Ferry set the outside temperature to a low level so I could see the way the wing anti-ice system turns off during takeoff and then back on after power is reduced.

On the day we flew, the wind at Istres Air Base was nearly calm and the temperature 68 degrees F, with a few wispy high clouds in an almost clear sky. Takeoff weight was 57,900 pounds with 12,040 pounds of fuel, well under the 77,460-pound maximum takeoff weight. For our flight, Vr and V1 were 115 knots and V2 120 knots. Ferry was in the right seat and I was in the left seat, while Valette flew in the jump seat. Corsia kept tabs on us from the salle d’ecoute, the telemetry monitoring center at Istres, where she maintained direct radio contact with us during the flight.

After waking up the 6X and starting the APU, I twisted the start knob and watched engine 2 and then 1 run through their start-up process. We would be staying in the vicinity of Istres and Marseille, so no complicated flight planning was necessary.

I released the parking brake and started taxiing toward Runway 15, which is 12,303 feet long. At first, I overcontrolled the nosewheel steering; it is somewhat sensitive but as I soon figured out, precise and easy to operate smoothly. Once on the long parallel taxiway, I managed our speed with the occasional deployment of thrust reversers to avoid too much use of the brakes.

With slats/flaps set at SF2, Ferry had me hold the brakes on the runway and then apply full power before releasing the brakes.

Takeoff didn’t feel too different from the 8X in terms of handling, but we did get a hefty push from the two 13,500-pound thrust PW812D engines, which easily exceed the total 20,175 pounds from the 8X’s three PW307Ds. I gave the sidestick a gentle nudge at Vr and the 6X launched smoothly into the air.

When flying a fly-by-wire Falcon, I enjoy the simplicity of the flight control system, at least in terms of pilot interface, and the 6X is no exception, needing just a tiny nudge of the sidestick to set the climb flight path to 10 degrees. We soon accelerated out of the airport environment and sped up to 250 knots for the climb to 15,000 feet.

Flying out of Istres is always a pleasure because there is hardly any other traffic, perhaps another Falcon doing flight test work or some of Dassault’s Rafale fighters in the traffic pattern. But we pretty much have the airport to ourselves, along with a dedicated controller and Corsia in the salle d’ecoute. This 6X has a limitation during flight testing where we couldn’t retract the landing gear until the wheel speed dropped below 20 knots. So we had to wait until Corsia confirmed the wheels had slowed, then retract the gear.

It's been a while since my last 8X flight, so I can’t make a direct comparison between the handling of the two jets, but the 6X felt tight, responding instantly to my control inputs and flying precisely as I wished. Dassault’s flight path-stable fly-by-wire design is familiar enough by now that I found it natural to select the desired flight path and then barely touch the sidestick until I needed to make a change to the flight path.

On the way to 15,000 feet, I turned while climbing to try out the controls. Then, once we leveled off, I flew some 30-degree, then 60-degree banked turns. This 6X has only one HUD for the left-seater, and I took full advantage of it, putting the flight path marker on the zero-pitch line to maintain altitude during the turns. For shallow turns, there’s no need to pull back on the stick to maintain altitude; this is all done automatically once the turn is entered. For the steep turns, I did have to pull back a bit and hold the bank with the stick as the flight control system tries to encourage the pilot to return back toward a less steep, more comfortable (for the passenger) section of the flight envelope.

I pulled the power back to idle for a Vmin demonstration and watched on the HUD and PFD as an AOA symbol moved down toward the flight path vector, indicating that we were nearing a stall. Before that could happen, however, the flight control protections lowered the AOA to prevent the stall, which would have happened at 120 knots. With the landing gear up but slats/flaps 2 selected, I held the sidestick all the way back and we slowed to 110 knots while I banked from side to side. There was quite a bit of pressure on the stick while I pulled it back, but that is the protection trying to counter the pilot’s action and prevent a stall.

After cleaning up the airplane, I moved the power levers to the maximum climb power detent and headed for FL400 at 260 knots and then Mach .78. Climbing through FL300, the rate of climb was 2,400 fpm and at FL350 1,700 fpm.

At FL400, I replicated the 30-degree turns and slow flight that I had just done at 15,000 feet, and the flight control system faithfully gave me the same experience. I didn’t have to change the way I flew the airplane just because we were higher and closer to corners of the flight envelope where you have to be more careful. The 6X behaved admirably and just as responsively as at the lower altitude.

After pulling the power to idle, I pushed the nose down to descend, remaining within a flight test limitation of Mach .90 or 350 knots. I reached to the center console to apply AB-1 and then -2 to feel the reduction in vibration compared with the 8X. With AB-2, there was a gentle rumble but other than the faster descent rate, hardly any feeling that the airbrakes were deployed.

Leveling off below FL150, I did some maneuvering with various airbrake settings, then a Vmin demo with SF3 and landing gear down so I could feel the handling in the landing configuration. Again, I pulled the sidestick to the aft stop and held it there and the 6X got quite slow, not too much above 100 knots, while it banked from side to side.

One of the flight control system’s degraded modes is direct law, and Ferry switched to that so I could feel how the handling changes. In this mode, there are no protections and the controls feel more like those on a conventional non-fly-by-wire airplane. I tried various maneuvers, using gentle control inputs, then Ferry reset the controls back to normal.

For our first landing with SF3 set, I set up an approach to Runway 15 at Istres, and on final, Ferry had me align the 6X with the taxiway and then at 500 feet agl slide over to line up with the runway, so I could assess controllability while close to the ground. The 6X handled like a much lighter airplane, and it was easy to point the nose exactly where I wanted while the autothrottle helped keep the 6X on speed.

At 200 feet, Ferry called for a go-around and I pushed the TOGA button on the side of the power lever. The autothrottles quickly advanced while I pulled back on the sidestick to set a climb attitude, then I pulled the power back to level off at 1,500 feet in the right-hand traffic pattern. The second approach, also with SF3, was to a normal landing, although I got a bit low on the right base and I could feel the autothrottles advancing when I held the nose up to keep from getting even lower. After turning final, speed and altitude were on target, and I proceeded to my first 6X landing, which as Ferry had predicted was a “kiss landing.” The view on final gives the pilot plenty of visibility and the nose attitude is relatively low, making it look as if it will be necessary to pull the nose up in the flare to make sure the main wheels touch first. But I resisted that feeling and after making sure the power levers were at idle descending through 50 feet, I made some small corrections with the rudders to align with the centerline and just barely pulled back on the sidestick. Then the 6X was rolling on the main wheels with absolutely no firmness to the arrival. I let the nose drop, then deployed the thrust reversers briefly, needing no braking to slow down.

We taxied back to Runway 15 for another takeoff. This time, as we passed Vr, Ferry pulled the right engine to idle and I continued the takeoff without needing any abnormal moves other than a small amount of left rudder to keep on heading. I maintained V2 + 10, then accelerated to 160 knots briefly until it was time to level off at 1,500 feet for the right downwind.

This landing was with the “good” left engine still producing power, and trying to avoid getting too low on base, I held altitude too long and ended up too high and too fast on final. The 6X made me look good, however, and easily adjusted to my errors. When I stopped trying to work so hard to get back on track, the 6X settled down and the rest of the approach started to look more normal, albeit at a slightly higher Vref due to the one engine out. The result was another perfectly smooth landing.

Entry Into Service

Dassault is preparing for first delivery of the 6X in mid-2023. Its 6.5-foot-tall and 8.5-foot-wide cabin offers 1,843 cubic feet of volume, a 3,900-foot cabin altitude at FL410, and a variety of interior configurations with 12- to 14-passenger layouts. A skylight in the galley was pioneered in the 5X design and helps bring more natural light into the 6X. Larger windows than on previous Falcon models add even more light to the cabin. The 155-cubic-foot baggage compartment is accessible in flight, plus there are another 76 cubic feet of unpressurized baggage space.

At maximum takeoff weight, the 6X’s balanced field length for takeoff is 5,840 feet and landing distance is 2,480 feet, thanks to a typical landing weight Vref of 109 knots. The 6X continues Dassault’s tradition of flexibility, allowing short flights followed by long-range flights without refueling. In one example given by Dassault, the 6X can complete a five-stop round-robin trip without refueling, starting and finishing in London via Geneva; Rome; Warsaw, Poland; and Stockholm. Another example has the 6X flying a “short hop” and then another 3,850 nautical miles unrefueled.