Boeing has decided to develop the 777X, its next-generation 777 derivative, with the same lower cabin altitude as the 787, despite the continuing use of a conventional aluminum fuselage structure.

The surprise decision means that 777X cabins will be pressurized to the equivalent altitude of 6,000 ft. rather than the standard 8,000 ft. altitude of conventional aircraft, including the current 777. Boeing introduced the lower altitude setting for the 787 because of the newer model’s stiffer composite construction. The resulting higher humidity levels and lower altitude conditions provide better passenger comfort on longer flights and have been specifically requested for the 777X by airlines within the launch customer group.

Scott Fancher, senior vice president and general manager of Airplane Development at Boeing Commercial Airplanes says “when we designed the 787 we took advantage of the materials capabilities of composites to design the features we wanted in the fuselage. The story of the 777X is slightly different.  Although it will have a new composite wing the aluminum fuselage is a minor model derivative of the 777 and will have sculpted frames, be 10 abreast and have bigger windows. We have made this decision because we know the fuselage really well.  We’ve been building it for years and developing incremental improvements, so we figured out a way to embed these features in this fuselage.” The move to incrementally add the lower pressure altitude represents a “truly modest investment.”

Launched in November 2013, the 777X marked the firm configuration design milestone in April and is now into the detailed design phase.  “Engineering releases are occurring on or ahead of schedule and we are seeing engineering quality like we have never seen before,” says Fancher. “We remain on track for firm configuration next year,” he adds. Production of the 777X, which has amassed 300 orders and commitments from six customers so far, begins in 2017, with first delivery for the larger 777-9X variant targeted for 2020.