The wing also has 33 deg. of sweep at quarter chord to reduce Mach-induced drag. The large, outwardly canted, highly swept winglets help reduce wingtip vortices, an important design feature considering the wing's modest 7.73:1 aspect ratio. The airfoil thus is optimized for Mach 0.855 cruise. The G650 is the first large-cabin Gulfstream to have an area ruled aft fuselage to reduce high-speed interference drag between the engine nacelles and fuselage.
The result is an aircraft that can cruise for 7,000 nm at Mach 0.85+ and 6,000 nm at Mach 0.90. It also consumes less fuel while cruising at Mach 0.85 than any rival in production. It is the first purpose-built business jet that can fly from New York to Tokyo, Seoul or Beijing in well above ISA (international standard atmosphere) conditions.
Most G550 systems are carried over, but have been updated to improve redundancy, simplicity and reliability. The electrical system, for instance, has many more backups because of the aircraft's digital fly-by-wire (FBW) controls.
Two engine-driven 40 kilovolt ampere (KVA) constant-speed generators and a 40 KVA auxiliary power unit (APU) generator supply 115/200 VAC, three-phase, 400-hz current mainly for motors, heaters and battery chargers. A 15 KVA ram air turbine provides a fourth source of emergency AC power.
Two 28 VDC, 53 AH nickel–cadmium (Ni-Cad) main batteries supply power for APU starting, and two 24 VDC, 9 AH Ni-Cad emergency batteries, plus backup flight control hydraulic power pack emergency batteries.
Gulfstream engineered a five-channel FBW flight control system for the G650, which saves 100 lb., eases rigging of flight control surfaces, offers more redundancy than a conventional hydro-mechanical system, and eliminates control cables, pulleys and linkages.
Direct law is used for takeoff and landing. Up and away, the primary high-level pitch control law is Nz, or vertical acceleration, command with “U” speed stability, meaning the pilot has to trim pitch for speed changes.
While most aircraft with fully powered flight controls need three separate hydraulic systems for required redundancy, Gulfstream instead uses remotely located, DC-powered pumps in hybrid flight control actuators in lieu of the third system. G650 thus retained the dual 3,000-psi hydraulic circuit design of its predecessors.
The main landing gear is a trailing link design for smooth touchdowns. The aircraft has a brake-by-wire system, but no auto-brake function.