Conventional Structure, Advanced Systems
Construction of 5X components is well underway at and its subcontractors. No surprises here. Similar to all previous Falcon Jets, Dassault will use high strength aluminum alloys for most of the primary airframe structure of the Falcon 5X. Most of the parts will be joined with conventional hardware. A few components will be fused together using friction stir welding, a first for a Falcon Jet. Composites will be used for the empennage, engine nacelles, fairings and radome, among other secondary structures.
Work share is similar to that on the Falcon 7X, with Dassault building the forward and aft fuselages, plus the wings; Daher-Socata is constructing most center fuselage parts; and Fokker is making the composite empennage with extensive use of resin transfer molding. In addition, Belgium's SABCA is building the aft, lower center fuselage section; GKN is constructing the wing's aft control surfaces;'s supplies the nacelles as part of the integrated powerplant package; Corsica's Corse Composite Aeronautique is building the wing to body fairing; and Potez, in southwest France, is supplying the main entry door.
The aero loft contours depart from those of previous Falcon Jets, starting with the 779-sq.-ft. clean-sheet wing, the first Dassault airfoil to have winglets as part of the initial design. It features a straight leading edge, a relatively modest 33 deg. of leading edge sweep and a 5% to 10% better lift-to-drag ratio than the airfoil of the Falcon 7X. High-altitude Mach buffet boundaries should be at least 15% better than those of legacy large-cabin Falcon Jets. And the wing weighs 500 lb. less than that of the Falcon 7X because of improved structural efficiency, in part due to the wing's straight leading edge that makes possible a wider chord, more rigid internal wing box.
The signature cruciform Falcon Jet tail design is retained, but the horizontal stabilizer has no anhedral.
The nose has completely new loft contours, including cockpit windows that are 32% larger than those of the Falcon 7X. This will make it much easier to see over the nose during takeoff, approach and landing. The flight deck is considerably more comfortable, including increased headroom and sufficient room aft of the pilot chairs to recline either one to 130 deg. for short crew rest breaks.
There's also a new jump seat for a third crewmember that stows full size behind the right pilot seat. It slides laterally into position in the center aisle and it pivots and reclines for greater comfort — a welcome replacement for the origami-like folding jump seat of older Falcon Jets.
The 5X will be the first Falcon to have a primarily AC electrical system, one with starter-generators that will produce 115/200 VAC, three-phase, variable frequency power. AC power, supplied by either the APU or GPU, also will be used to start the main engines, a departure from the air turbine starters and DC starter-generators used on legacy Falcon Jets. AC power will also be used for high electrical loads, including windshield and probe anti-ice heating along with cabin management and IFE systems. Two 35 AH sealed lead-acid batteries will anchor the DC electrical system, used for critical power functions such as the digital flight control system (fly by wire). Transformer rectifiers will convert AC to DC. The overhead electrical control panel has been simplified and the electrical system has enhanced automatic bus tie functioning to protect it in the event of malfunctions.
The dual-redundant 3,000-psi hydraulic systems are simpler than the triple-redundant systems of the Falcon 7X. Four engine-driven pumps supply System A and System B hydraulic circuits, each one having left and right engine-driven pumps. System B also has a DC standby pump. Systems A and B also have electrically powered, backup subsystems that power some of the flight control actuators in the event of dual failure of the normal hydraulic system. MIL-H-5606 is retained as the standard for hydraulic fluid.
The fuel system is vintage Falcon Jet, having pressurized tanks and dual-redundant fuel boost pumps.
Heroux Devtek will supply the landing gear, with soft landing touchdown assured by trailing link main gear and a dual chamber olio nose gear. The steer-by-wire system will be controlled through the digital flight control system. Notably, the nose gear doors will be closed when the gear are fully retracted or extended, greatly reducing cockpit noise during landing approach. Meggitt will furnish the dual-channel brake-by-wire system with high-energy carbon heat packs. Remote tire pressure monitoring and brake temperature indicating systems will be optional.
If the air-conditioning and pressurization system follows the 7X design, there will be a second emergency “pack” having only heat exchangers, but no turbine, compressor and fan.
Similar to legacy Falcon Jets, the Falcon 5X will have a single air-cycle machine pack. It's supplied by Liebherr. There will be separate temperature controls for the cockpit, galley, and forward and aft cabin. The Falcon 7X only has a three-zone system.
The 9.9-psid pressurization system will provide a 3,900-ft. cabin altitude at FL 410 and a 6,000-ft. cabin at FL 510. On most long-distance flights, cabin altitude won't exceed 5,000 ft. because the aircraft normally cruises at or below FL 450.
The digital flight control system, designed and built by Dassault, is based upon the Falcon 7X architecture, but it will integrate more functions. In addition to carefree handling, flight path stability and envelope protection, the fly-by-wire (FBW) system will host control of mid-span flaperons that can function as ailerons, flaps and/or spoilers.
The cockpit will have left and right sidestick controls; three main or primary, dual-channel flight control computers that host normal, alternate and direct law functions; plus three backup, or secondary, single-channel flight control computers that only host direct law functions, including yaw damper. Unlike the Falcon 7X, the Falcon 5X won't be fitted with an analog emergency computer used for temporary control to be used only in the event that all six main and backup flight control computers fail. But the aircraft can be dispatched after any single electronics failure.
Most primary and secondary flight control surfaces will be hydraulically powered. But in a departure from the Falcon 7X, the trailing edge flaps will be electrically powered rather than hydraulically actuated. Use of flaperons is a first aboard a business jet. When the crew selects speed brakes 1, for instance, the outboard ailerons will deflect up while the mid-span flaperons will move down, thereby increasing drag while minimizing wing bending moment. The flight control surface geometry also virtually eliminates turbulence over the horizontal tail that's felt as airframe buffet. The new function especially will be appreciated by passengers when the aircraft is descending with bleed air anti-ice on. Engine power must be increased for adequate bleed air supply. During descents, the speed brakes on older Falcons had to be used to control speed with anti-ice on. That should no longer be necessary with the split aileron/flaperon function.
The 5X has conventional air brake panels, but they only begin to deploy when speed brakes 2 is selected.
The split aileron/flaperon geometry, along with the aircraft's full-span leading edge slats, will be key to enabling Dassault to earn steep approach certification for the 5X, enabling it to use.
Bleed air will be used for wing leading edge and engine inlet anti-ice heating. Unlike previous Falcon Jets, pilots will be able to select wing anti-ice while on the ground. It automatically will activate with weight off wheels.Hamilton Sundstrand in San Diego will furnish the ground-use-only APU.