We checked Mach buffet margins with a wind-up turn, which indicated the aircraft has robust margins, albeit at a comparatively light weight. We didn't encounter buffet until about 1.4g at Mach 0.88 in a 45-deg. turn.
Descending to 15,000 ft. for airwork, we used idle thrust and air brakes. We noticed only mild buffeting and a slight pitch change when the air brakes were extended.
Once level at 15,000 ft., we flew a series of standard air work maneuvers. We especially wanted to evaluate stall behavior because G650 is the first large-cabin Gulstream that does not need a stick pusher to hasten stall recovery. We first attempted a stall in the clean configuration at a weight of 66,800 lb.; we trimmed the aircraft for a 156 KIAS Vref speed or 0.67 normalized AOA (angle of attack), reduced thrust and decelerated. “Normalized” means that 1.0 AOA is the maximum lift coefficient adjusted for high-lift configuration and local Mach number because of its influence on buffet and stall.
During the approach to clean stall, the stall warning stick shaker fired at 129 KIAS or 0.94 normalized AOA. At 0.97 AOA, the FBW system limited elevator and horizontal stabilizer pitch control authority to prevent untoward handling characteristics. Holding the control wheel fully aft, the nose gently pitched down and we initiated recovery.
The dirty stall, with gear down and flaps extended to the full 39 deg., was equally non-dramatic. We trimmed for 122 KIAS or 0.67 AOA, began a normal glidepath-like descent and then leveled off without adding thrust, thus allowing the aircraft to decelerate. After the stick shaker fired, we continued to pull aft on the yoke until reaching the stops. At 0.98 normalized AOA, the nose gently dropped and we initiated recovery with only a slight loss of altitude.
Returning to Savannah, we prepared for a WAAS LPV (wide area augmentation system with vertical guidance approach procedures) to Runway 19. Horne computed Vref at 120 KIAS for a 65,500-lb. landing weight and a non-factored landing distance at 2,873 ft. based upon 13-kt. headwinds.
We bugged the target airspeed at 125 KIAS and let the auto-throttles maintain speed in gusting wind conditions.
The HUD's azimuth and glidepath guidance cues, along with the FPV marker, made it easy to hand fly the approach.
The FBW system transitions from high-level control law to direct law for takeoff and landing, so G650's smooth handling behavior during final approach reflects its aerodynamic refinement. At 50 ft., we pulled back the thrust to idle and continued to use the HUD until touchdown. We deployed the thrust reversers, lightly touched the brakes and turned on to a taxiway after a touchdown roll of about 5,200 ft.