The Boeing 747-8 wing

The 747-8’s wing is not a modified 747-400 wing. It is a new design, developed using computational fluid dynamics and validated in wind tunnel testing, and it is the single biggest engineering change between the two aircraft.

What the new wing does

Boeing lists the changes as:

• Advanced technology airfoils for improved overall performance and greater fuel capacity.
• Fly-by-wire spoilers and outboard ailerons to save weight.
• Double-slotted inboard and single-slotted outboard flaps to improve low-speed performance and noise.
• Advanced-technology raked tip to reduce cruise drag.
• Aileron droop to reduce noise and provide improved low-speed performance.
• Redesigned flap tracks with optimised flap-track fairings to improve low-speed performance and noise.
• Redesigned Krueger flaps with gapped configuration to improve low-speed performance.

Together these give improved aerodynamics and larger fuel capacity, while allowing the aircraft to cruise as fast as or faster than any other passenger aircraft.

Raked wingtips instead of winglets

The most visible change is at the tip. The 747-400’s upright winglets are gone, replaced by raked wingtips — an extension swept sharply back rather than turned upwards — which increase lift and reduce drag at cruising speed.

Manoeuvre load alleviation

The wing’s fly-by-wire spoilers and ailerons make possible a flight control feature called a manoeuvre load-alleviation system. Pioneered on the 787 Dreamliner, it changes the distribution of lift across the wing during non-normal flight conditions, reducing the load carried by the outboard section.

The payoff is structural. Because the wing never has to absorb the peak outboard loads it otherwise would, Boeing was able to make the structure smaller — saving about 1,400 pounds without compromising structural integrity.

Flaps, ailerons and noise

Several elements of the design target noise as much as performance. When the flaps are extended, the ailerons automatically deflect and act as additional high-lift devices, improving takeoff and landing performance while reducing noise. The redesigned flap tracks and their fairings, and the gapped Krueger flaps on the leading edge, work to the same end.

The result, by Boeing’s figures, is a noise footprint about 30 percent smaller than the 747-400’s. That has an operational consequence: Boeing said the 747-8 would be able to use London Heathrow around the clock, where most aircraft face a night curfew on noise grounds.

What it adds up to

Boeing’s case for the 747-8 rested heavily on this wing and the GEnx-2B engines hung beneath it. The company positioned the aircraft as the only passenger type in the 400–500 seat market, with engines burning about 16 percent less fuel per seat than the 747-400’s and around 11 percent less than the Airbus A380’s.