By now you have no doubt read that the big cabin, ultra-long-range Falcon 7X uses fly-by-wire technology to connect the human pilot to the flight controls, a first for business jets. Falcon insists on calling this a digital flight control system (DFCS) because all of the computers are digital, not analog, but to a pilot the intrigue is that there is no mechanical link between the cockpit controls and the surfaces that actually guide the flight path of the airplane.
So what is it like to fly the Falcon 7X? Not like any other business jet, that’s for sure. And not exactly the same as any of the airline jets that use fly-by-wire technology because each airplane manufacturer has its own concepts of how an airplane should fly to best conduct its mission.
Dassault has been building extremely capable military fighters using DFCS for 25 years and it is that experience that most directly flows into the flying characteristics of the 7X. Obviously, a fighter has to be very maneuverable, and the 7X is, but less apparent in a modern fighter is the requirement for smooth and steady flight with minimum demands on the pilot. While jinking around in a dogfight is a necessary capability, the common mission of a fighter is to deliver weapons to ground targets or to shoot over the horizon at other aircraft. In both cases, a stable and steady pass is the best guarantee of success.
When it comes to the business jet mission a smooth and stable flight with the precision to make a safe and predictable touchdown in the worst weather is what everybody wants — particularly the passengers. So in the 7X the computers at the heart of the DFCS keep the airplane on a steady flight path until the human pilots or autopilot asks for a change. The computers automatically correct for any gusts or turbulence that displace the 7X from its present flight path, which keeps the airplane traveling to where you want it to go, but also has the unintended effect of smoothing the ride. Because the DFCS system instantly makes very small control movements when the 7X hits turbulence, the bumps, wallows and rolls that other airplanes experience are minimized. That long and very flexible wing also helps damp out the jolts of turbulence that are transmitted to the cabin.
But back to what it’s like to fly the 7X. The best way I can describe it is that you point and shoot. Put the 7X on the flight path you want to maintain, and it stays there until you make a new control input.
The sidestick is nice and beefy with a substantial grip and rather long travel in any direction. You move this stick rather than simply applying pressure with very little displacement as on some other sidesticks. There is a very positive centering spring so the stick returns to neutral as soon as you release pressure. The two sticks are not connected mechanically so only one moves at a time, but if both pilots make simultaneous inputs, the sticks shake to warn that only one can fly at a time. A priority select switch can give one pilot the ability to override the other’s inputs.
The sensation of flying the 7X is immediately natural with the airplane responding smoothly, and exactly as I expected, to stick movement. However, once the airplane is heading where I want it to go, I notice the difference because I have always had to trim off the stick force in every other airplane. But not in the 7X. When the flight path indicator on the primary flight display (PFD) is on target, you simple release pressure and the stick centers and the 7X stays on that path. It only takes a couple of minutes to forget about trim, but after a lifetime of flying other airplanes, it comes initially as a pleasant surprise.
For example, on rotation for takeoff you are holding the same stick force against springs when the flight path reaches the target as you were when you started to bring the nose up. In any other airplane if you release back pressure the nose will drop, seeking its trim speed, so you have to hold the stick back until you can trim off the pressure. But the 7X is constantly trimming automatically to maintain a constant flight path.
One of the most impressive displays of the way the DFCS holds flight path is by making huge airspeed changes. In level flight, hands off, I pushed the power and airspeed up to 300 knots indicated and made no flight control inputs while the 7X held a steady flight path. I then brought the power back to flight idle, and as speed limits were reached, extended slats and flaps, again hands off, and the flight path remained constant. The attitude of the airplane changed enormously from nearly level to way nose up, but the DFCS held the flight path.
The 7X allows pilots to think about the mission in a new way. Instead of concentrating on how to make the airplane go where you want it to, you can focus on where you want it to go. The 7X completes the design logic loop and makes ultimate use and sense of the EASy glass cockpit, which displays flight path instead of attitude as primary. You see the flight path on the PFD, you see the flight path command, and you adjust the path to where you want it, and it stays there. Pilot workload is cut to a fraction of what it takes to fly a conventional airplane.
The 7X is the first “all new” Falcon since the three-engine Model 50 was developed in the 1970s. The big cabin 900 series and the twin-engine 2000 family are all derivatives of the excellent work done on the 50. Dassault has pioneered the use of computer aided design (CAD) and created the CATIA system that is used in all sorts of product design, including by Dassault’s competitors. Though the company has used computers in the design of all of its airplanes since the Falcon 50, the 7X is the first that is truly a virtual design. Human experts used computers in every phase of the creation to optimize performance of the finished airplane, as well as to minimize weight, streamline manufacturing, and reduce maintenance requirements and complexity. And as final proof that aviation is now a complete and total global enterprise, all original documentation of the 7X was done in English, a big step for the French.
Dassault used what it calls “product life management” teams linked by computers with 400 people working on the design, even though they were spread across seven countries. Major airframe elements are built by half a dozen different companies and are brought together for final assembly at the Dassault facility in Bordeaux. The unfinished “green” airplanes are flown to Little Rock where all paint and interior completion is done. All business jets are at least a little international efforts, but the 7X is truly a global product from initial design to final completion, and support when in service. The 7X was the first business jet to be certified jointly by the FAA and the European authorities.
What didn’t change in design of the 7X were Dassault’s basic assumptions about intercontinental range airplanes, foremost being that they should have three engines. The 7X is undoubtedly the most technologically advanced business jet yet, but the company sticks to its conservative streak when it comes to the number of engines you should have when launching out over a big ocean. While the rest of the industry has moved to an extended twin engine operation (ETOPS) position that allows enormous twin engine airline jets to roam four hours away from a suitable alternate, Dassault and Falcon owners just feel more comfortable with that third engine. And the 7X is so comparatively light, and the design so low in drag, that even with three engines it has the best fuel efficiency in the ultra-long-range business jet class.
Another benefit of the third engine is on takeoff. The rules require that you calculate a takeoff path with the most critical engine failing at decision speed on the runway. So twin engine jets have to meet the takeoff flight path minimums with half the power gone, but with three engines you only lose one third of the power. That means the 7X can use shorter runways, or thinking of it the other way, it needs less total power for the same runway requirement, which is part of the reason for its excellent fuel efficiency.
A center engine has an aerodynamic advantage, too, in that it makes the airflow behave as though the fuselage were longer. The high velocity exhaust of the center engine helps smooth the air flow over the aft part of the fuselage just as though there were a long, tapering tailcone. You can see the impact of this phenomenon by comparing the twin-engine Falcon 2000 with the 900. The 900 cabin is 7 feet longer than the 2000 cabin, but the overall length of the fuselage is the same because Dassault had to extend the tailcone of the 2000 to make up for the missing aerodynamic effects of the center engine exhaust.
Lower fuel burn compared to other airplanes with similar-sized cabins is doubly important these days with the requirement to account for, and pay for, our carbon emissions. When you burn less fuel you save twice — at the pump, and when picking up the carbon offset bill. Being headquartered in Europe, Dassault was aware of the carbon issue before it become apparent in the United States, but in any case, paying for carbon emissions is now a fact in Europe, and will probably also be a reality in most of the world soon.
The 7X cabin cross section is essentially the same as the Falcon 900 and 2000 family with 6-foot 2-inch finished headroom over a flat floor. Cabin width is just 2 inches short of 8 feet at its widest point. Passengers have been very happy with the space and comfort in the 900 so Dassault stayed with it, but stretched the length out to just over 39 feet, about 7 feet longer than the 900. There is plenty of space for three separate seating areas, a big forward galley and crew rest area and lava-tory, large passenger lavatory in the rear, and access to the aft baggage compartment in flight. And Dassault has upped the cabin pressurization differential to 10.2 psi so the cabin altitude will be only 6,000 feet when the airplane is at its 51,000-foot ceiling.
One big change to the 7X fuselage is the windshield, which is the first curved windscreen in a large Falcon. All other Falcons have an array of seven flat panels. Visibility from any Falcon cockpit is good, but it’s better in the 7X, and the curved windshields blend more smoothly into the canopy to reduce drag and slipstream noise. And Dassault gave passengers a better view with more and larger windows, so the 7X has 30 percent more window area than a 900.
The previous Falcon wing designed initially for the 50 is a first generation “super-critical” design that was remarkably efficient for its day. However, significant advancements in airfoil design have been made over the years and the 7X wing incorporates many of those. Most noticeable is the span, which at 86 feet is about 20 feet longer than the Falcon 900 wing. And at the tips are tall and graceful winglets, something of a surprise on a Falcon since Dassault had maintained for years that a “properly designed wing” doesn’t need winglets. But it turns out that a properly designed winglet benefits almost any wing, particularly for an airplane intended to cruise at very high altitudes over very long ranges.
What a well-designed winglet does is manage the flow of the high-pressure air under the wing as it escapes around the wing tip. The winglet makes the air behave as though there was more wing there, and in general more span equals less drag and more lift. Dassault has teamed with Aviation Partners, creator of the blended winglet, and is adding them to the 900 and 2000 to boost performance, particularly range. No doubt Dassault’s anti-winglet position had much to do with competition with its archrival, Gulfstream, which has had winglets on its jets for more than 25 years. But this time aerodynamic science won out and all are benefiting from the performance edge that can be mined at the wing tip. And the winglets look great. A wing without them can be an excellent performer, but the winglets sure do add a big element of style, whether it’s on a Boeing or a Falcon.
The 7X also has more wing sweep than other Falcons with 34.5 degrees. More sweep helps reduce drag at high-speed cruise, but sweep is also destabilizing and a jet can have undamped Dutch roll. Conventional jets manage this issue with multiple yaw dampers, but DFCS computers automatically manipulate the controls to maintain stability. As with other Falcons, the 7X wing has leading edge slats that help keep airflow attached to the upper wing surface at low airspeeds and high angles of attack. The slats deploy with the trailing edge flaps and also automatically deploy if the airplane approaches a stall.
The 7X wing is also limber, flexing 9 feet at the tip when limit load was applied to the static test article. An important benefit of DFCS is that it provides envelope protection, meaning the computers won’t allow the 7X to exceed speed and maneuvering limits. That means no extra structure has to be added to compensate for a bungling pilot who could overstress the airframe. The result is a lighter airframe, which always equals greater efficiency.
The 7X is the first Falcon to have a trailing link main landing gear. Because the wheel axle is located aft of the main gear strut there can be a long travel of the shock absorber, which does wonderful things to the smoothness of your landings. The 7X wheels and tires are also much larger than other Falcons and that also makes for smooth landings. Even on taxi the big tires roll over the expansion joints and centerline lights without the jolts delivered by the rock-hard smaller tires mounted to the vertical landing gear strut of other Falcons.
The sturdy gear and overall strength of the 7X airframe give it a very high maximum landing weight as a ratio of its maximum takeoff weight. The 7X can land at 62,400 pounds, which is 90 percent of its 69,000-pound max takeoff weight. That means you can fly a short hop with full fuel you bought at a lower price, and still depart on a flight of nearly 5,000 nm without adding more fuel.
The cockpit of the 7X looks a lot like the other Falcons because it is dominated by the four huge flat screens of the EASy avionics system. The PFD in front of each pilot displays everything you need to fly the airplane, including all flight path information, flight director guidance, communication and engine and primary system information. The two equally large multifunction displays (MFDs) stacked in the center can be accessed by either pilot and can show every bit of information you can imagine about the flight and the airplane.
The EASy system is controlled primarily by two big trackball curser control devices mounted on the center pedestal. You rest the palm of your hand on the top of the CCD and manipulate the ball with your fingers so it’s easy to operate under any flight conditions. Buttons to the sides act as “enter” keys. The EASy system — a name derived from an internal Dassault acronym for enhanced avionics system — guides you through each phase of flight with little airplane symbols showing departure, cruise, arrival and approach. Click on the phase of flight and the system has a high degree of anticipation, knowing where you are and filling in information to get you to where you want to go. There are keyboards as in other systems, but very little key punching is required because most data entry can be made by pointing and clicking short menus of appropriate options.
Dassault has made remarkable and welcome strides in cockpit automation with the 7X. Most noticeable is that the circuit breaker panel is gone from the cockpit. Those dozens and dozens of push-pull CBs that line the cockpit walls and overhead of other jets are replaced by remote CBs located closer to the equipment they protect. If a CB pops in flight you get a crew advisory message (CAS) and fly on because you can’t reset it in flight, and everything necessary is triple or more redundant.
Dassault people want to discuss the levels of system redundancy forever, because, well, there is so much to say. They worry that pilots and passengers are concerned that the DFCS is new, and totally automated, so they need to explain all the steps taken to ensure there will always be electrical and hydraulic power for the multiple levels of computers that are DFCS. Let me summarize. There are three engine-driven generators, two permanent magnet alternators, a wind-driven ram air turbine generator (RAT) and finally two batteries, any one of which can power the DFCS. There are three main hydraulic systems powered by five engine-driven pumps, one standby pump and bootstrap type reservoirs. You only need one to get back to the airport.
The entire range of critical systems exceeds 109 (one in a billion) probability of failure, which is the same standard for wing spars and other primary structure. I trust Dassault implicitly to build a wing strong enough to meet the 109 standard without me counting spars. I feel the same about the redundancy of the systems, including the DFCS. 7X pilots will spend five weeks learning about the backup systems upon backup systems in training at CAE, which has a spectacular 7X simulator, but then will undoubtedly fly their careers without seeing the backups in action. And, in any event, the level of automation is so high that little, if any, crew action is required when something fails.
The high level of cockpit automation has Dassault almost insisting that crews use a true checklist rather than a “do list.” In most airplanes a pilot reads a command on the checklist and then acts on that command. That’s a do list. In the 7X there are very few buttons or switches to move to get going, and they flow very logically from the overhead down to the pedestal, so you move the switches, press the couple buttons, get the engines started, and then consult the very short checklist to make sure you didn’t forget anything. Even if you did, there would be a white, yellow or red, depending on importance of the item, CAS message telling you what you forgot.
The 7X is the first Falcon without a tiller to control nosewheel steering, so you use the rudder pedals. I found it very easy and natural to maneuver the 7X because the DFCS adjusts nosewheel deflection to suit your speed. At slow taxi speeds you can spin the 7X on the ramp with the pedals commanding 60 degrees of nosewheel deflection. But on takeoff and landing the effect of pedal inputs washes out so you don’t swerve at high speeds. An important feature is that the pedals have a strong centering spring, so when you want to taxi straight just release all foot pressure and the airplane goes straight. Other jets I have flown with pedal steering lack a centering spring, so you have to kind of lock your legs in position to taxi straight ahead without unintentionally moving the pedals.
The 7X has an autothrottle system but you don’t use it for takeoff as in other jets. Instead, you simply move the power levers full forward and the computers set takeoff power. It’s the same for go-around. Once up and climbing you engage the autothrottle with odd little buttons that are somewhat hard to reach on the back of the levers. Then you select the airspeed you want, or as assigned by ATC, or you turn the knob and have the system look up the optimum or required speed from the flight management system. I like the automatic airspeed selection because it observes the airport traffic speed limits, and then the transition speed limits, and finally goes to optimum performance climb. It does the same on descent and arrival, and if the STAR has airspeed limits it will automatically observe those, too.
It was a windy day with gusts to 35 knots when I got to fly the 7X at Istres, a military airfield in the south of France where Dassault has its flight test headquarters. With that much wind blowing from the north over the rugged Mediterranean coast of southern France, there was turbulence. The design of the 7X couldn’t overcome every disturbance, but I have to say the ride was excellent, with no sharp jolts and very little deviation from the present flight path.
At altitude I made steep 2 G turns at high speed, which are possible only by holding the stick over. If you release pressure on the stick in a steep bank the 7X will roll back and hold a constant bank angle of just over 30 degrees, the normal maximum bank angle for maneuvering any jet. But the DFCS gives the pilot the authority to roll the 7X to any angle by holding the stick over. And the roll rate is a brisk 60 degrees per second if you jam the stick hard over. However, during normal maneuvers the initiation of a bank is so smooth you couldn’t feel it if you closed your eyes.
The DFCS does not give pilots the same unlimited authority in pitch because the human could stall the airplane on the low end, or overstress the airframe on the high-speed side. If you pull the stick back to a flight path that there is not enough energy to sustain, the DFCS will yell at you and flash an urgent message on the PFD, but if you insist on pulling back it will automatically deploy the wing slats to keep the ailerons active at low airspeed. If you still persist and the autothrottle is engaged, it will automatically add power. If the autothrottle is not engaged, the DFCS will lower the nose to keep the 7X flying even though you are holding full aft stick. Other jets have stick pushers that grab the yoke out of a pilot’s hand to shove the nose over and prevent a stall. The DFCS accomplishes the same with total smoothness and always keeping the airplane near, but on the safe side, of the stalling angle of attack.
With the stick full aft the 7X has very positive and smooth roll control in any configuration. The DFCS is really helpful in a wind shear encounter because you simply add full power and full aft stick and the system keeps the 7X flying at the maximum safe angle of attack with no risk of a stall.
On the high-speed end the DFCS limits indicated airspeed or Mach to just a hair over the red line by raising the nose no matter how much you push on the stick. The autothrottle does its best to keep the airplane flying within the limits, but raising the nose to keep the 7X right on the limits is the final protection for the airframe. Again, not a new concept — many Learjet models had stick pullers to prevent an overspeed — but the DFCS protects the airplane with perfect smoothness and precision.
The 30-knot-plus winds were waiting for my return to the runway, but were blowing within 20 degrees of runway heading, so it was gusts and bumps, not a crosswind that would be the test. Thanks to its very effective leading edge slats and big flaps the 7X has very low Vref approach speeds, around 105 knots at typical weights. With the gusty conditions I maintained about 15 knots above Vref and found that the less I did with the stick, the better the approach was. I pushed over to aim the flight path marker at the touchdown zone and to match the VASI, and then left the stick alone. It is hard at first not to jump in and try to correct for every temporary attitude change made by the gusts and turbulence, but if you set it and watch, the DFCS does a spectacular job on approach.
As the radio altimeter calls out the height above touchdown you reduce power to idle and pull back on the stick to reduce the descent rate. My touchdowns were great on the trailing link gear and the spoilers deployed automatically to keep the wheels on the runway. Unlike other jets where you need to continue pulling back on the yoke, or at least hold back pressure to keep the nosewheel from banging down, the DFCS has a “de-flare” logic so you immediately release backpressure on touchdown and the system automatically and very smoothly lowers the nosewheel.
We pulled an engine back on takeoff and made another approach and landing, but again, the third engine means this was just an “abnormal” procedure, not an emergency as in a twin, so you use the same speeds and flap configurations as with all three turning. The rules require that it must be possible to hold the wings within 5 degrees of level using rudder only after an engine failure in a transport airplane, but the DFCS helps here, too. Even though the pilot only moves the pedals after an engine failure, the DFCS uses aileron and spoiler along with the rudder to hold the wings level so the rudder and fin can be smaller, lighter and create less drag than on a conventional airplane.
With its big cabin, 5,950 nm IFR range and 5,505-foot runway requirement for a max weight takeoff, the 7X is a remarkable airplane. As a pilot it’s easy for me to become absorbed in the technology of just how the 7X delivers so much runway performance, speed, range, comfort and safety, but the people who buy large business jets have also noticed and the airplane is sold out for several years in advance. The first all-new Falcon in many years is truly something special in every respect.
