The General Electric GEnx turbofan is one of the two new engine families under development for the 787, but will be the sole option for the new 747, in a 66,500-pound-thrust version which is designated GEnx-2B67. It has the same core but a different fan and fan case. Unlike the electrically driven 787, the 747-8 will use a traditional bleed-air system, one of the big differences that prevent both airplanes from using exactly the same engines.
Nearly half of the 15-percent per-seat fuel burn improvement over the 747-400 would come from the new engines. But aerodynamics and materials changes will also play a role in helping the 747 Advanced fly more efficiently. Most obvious upon casual inspection, the design shows a somewhat longer wingspan–nearly 225 feet compared with 211 feet in the -400–and raked wingtips, instead of the big six-foot-tall winglets of the 747-400. The wings will also feature a re-lofted airfoil and carry 2,600 gallons more fuel. On the trailing edge, the new design does away with the 747-400’s triple-slotted flaps, in favor of simpler and more maintenance-friendly single- and double-slotted devices.
The airplane will borrow little of the composites content of the 787, but will use some of the more exotic metal alloys from both the 787 and 777. From the 777, the 747-8 will also borrow flight deck features such as a closed-loop modifiable electronic checklist, multifunction common display units, a cursor control device and the big twinjet’s flight management computer. The 747-8 will also use the 777’s slightly larger passenger windows, which not only aids visibility but cuts the amount of metal used and, therefore, the weight of the fuselage.
Designed to fly 8,000 nm–some 850 nm farther than the 747-400–the passenger version of the 747-8 will connect nearly any city pair in the world, according to Boeing. The freighter version will fly 4,475 nm with the full structural payload, but operators can trade range for payload when loaded cargo densities are lower.
The maximum takeoff weight of the 747-8 will be 960,000 pounds, compared with the 747-400’s 875,000 pounds and the 747-400ER’s 910,000 pounds. The aft plug of 60 inches is common to both passenger and freighter version of the 747-8. The forward plug is 80 inches for the passenger version, which contributes to a new extended upper deck which Boeing has christened The Skyloft. The new freighter version dispenses with the upper deck extension, but has a 160-inch plug to provide space for the extra pallets.