Metallic wing ribs among the features as board prepares for crucial launch decision

Boeing has settled on metallic wing ribs for the 7E7, as it prepares to ask its board of directors for permission to offer the aircraft this month.

Boeing has also confirmed that it will follow the Airbus A380's lead and use a variable frequency electrical power system and a 350bar (5,000lb/in2) hydraulic system.

Randy Tinseth, Boeing Commercial Airplanes director of product and service marketing, says he is confident that Boeing's board will approve the offering of the aircraft "before the holiday shutdown at Christmas". A board meeting is scheduled for 15 December.

Tinseth also revealed that the 7E7 will have aluminium wing ribs under composite skin panels, although it is not known if all or just some of the ribs will be metallic. "The aircraft will be 50% composites by weight; 20% aluminium; 15% titanium; and 10% steel," he says. "This means the 7E7 Stretch will have an operating weight empty 9,100kg [20,000lb] lighter than the Airbus A330-200, for 3,150km [1,700nm] more range with 250 passengers," he says.

Some of the composite materials used will be laminates "much like the Glare material on the Airbus A380", he says. "Using laminates, a 'smart layer' of piezoelectric transducers can be sandwiched between composite layers," he adds, which would allow structural health monitoring. "We're looking at it for critical damage-prone zones," says Tinseth, "service areas such as doors and the aft fuselage for tailstrikes and heavy landings, for example." Tinseth also says that the use of so much non-corroding composite materials could enable Boeing to increase the basic lifetime of the 7E7 beyond the normal 20 years, but says this is still being studied.

Tinseth adds that the 7E7's cabin will feature environmental changes to reduce passenger discomfort on long flights. "The cabin altitude will be reduced from 8,000ft [2,400m] to 6,000ft, and we're also looking to increase the cabin air humidity," he says. Passive and active cabin noise reduction techniques are also being considered, although Tinseth says the current focus is on reducing specific sounds that can worry nervous passengers, rather than creating a "silent cabin". For external noise, Boeing's goal for the 7E7 is to meet London Heathrow's QC1 noise limit on take-off and QC0.5 on approach (Flight International, 1-7 July).

Source: Flight International