The Hawker 850XP winglets are made from high strength composites with a metal leading edge. Each winglet is 30-inches tall and angles outboard so its tip extends one and one-half feet further out than the previous Hawker wingtip, adding three feet to the total wingspan. The winglet does not require any ice protection, and it is faired into the wing in a continuous sweeping curve. A new lens covers LED position lights that have an expected life of at least 5,000 hours, which is important because it is the norm to turn on the nav lights whenever power is on the airplane, which is the way a Hawker awaits its passengers with the auxiliary power unit (APU) running to heat or cool the cabin.
The winglets on the 850XP use a "supercritical" airfoil with a deep cusp on the outer surface, which is the surface that corresponds to the bottom of the wing. A supercritical airfoil is one that minimizes the shock wave that forms when an airfoil reaches its "critical" Mach number. Critical Mach is the speed of the airplane at which air, accelerating to flow over and under the airfoil, reaches transonic velocity and a shock wave forms. The sonic shock wave generates enormous amounts of drag, almost as though a wall were stretched across the airfoil. A supercritical airfoil suppresses the transonic shock wave with its shape, which features a quite flat upper surface and a deep cusp on the lower surface near the trailing edge. The high-pressure air expanding into the cusp rejoins air flowing over the upper surface at the trailing edge in a smooth manner that prevents the shock wave on the upper surface from growing.
The addition of winglets to the 850XP called for minor internal wing structural changes that have not added inspection or maintenance requirements. In fact, a variety of small airframe improvements enabled Hawker to extend the basic inspection interval of the airplane from 300 to 600 hours.
If the winglets perform as expected, the 850XP should climb quicker and fly further, and it does. At maximum certified takeoff weight the 850XP climbs to 39,000 feet in two minutes less than the model 800XP it replaces. Once level in cruise, the 850XP is as much as five knots faster, and because the extra speed comes from reduced drag, not more thrust, range goes up more than 100 nm.
Combining quicker climb and faster cruise improves block speeds, but really pays off when flying into a headwind. The winglets add four percent to the 850XP's still-air range, but can add more than 25 percent range when going upwind. For example, the 850XP can fly nonstop between Teterboro and San Francisco, a distance of 2,225 nm, with NBAA IFR fuel reserves against 57 knots of average headwind. That equals Boeing's prediction of 80 percent worst case. The Hawker 800XP could make the trip nonstop against only 58 percent worst-case winds. That's a 27 percent improvement.
The other noteworthy improvement to the Hawker 850XP is the addition of the Collins integrated flight information system (IFIS) to the Pro Line 21 cockpit. A computer file server unit with cursor controls gives 850XP pilots the ability to show Jeppesen charts on either of the two big 8-by-10-inch flat panel displays in the middle of the panel. It also shows enhanced map overlays, and en route real time radar and other weather information from a variety of providers.