Boeing's 747-400X Stretch plan has been boosted by signs of new interest from Asian airlines, and the company's decision to offer a more capable 777-300X.
Speaking of renewed enthusiasm in the stretch proposal, director product marketing Joe Ozimek says: "Interest is coming back from Asian carriers, which are resuming fleet planning." The 747 stretch plan, and the preceding 747-500X/600X proposals, fell victim to the downcycle, but in the case of the baseline 747X, the delay has allowed Boeing to refine the design. The result, says Ozimek, is a proposal for a lighter aircraft, but with better performance.
Aerodynamic modifications, flight tested on an Asiana 747-400, indicate a revised design, combined with the original root insert, could fly between 15,000km (8,150nm) and 16,000km with 450-500 passengers. "This time we get the same range with a maximum take-off weight of 1,043,000lb [473.5t]," says Ozimek. The span is 4.6m (180in) wider overall, while wing area increases by 14% from 540m2 (5,825ft2) on the -400 to 615m2. The larger wingspan requires an extra inboard flap, while providing capacity for extra fuel in the enlarged wingbox. The wingbox is just over 1m longer, while the inboard wing is "relofted", providing more fuel volume and better aerodynamics.
While the larger wingbox stretches the fuselage by default, the bulk of the extension is made with a 4.6m stretch to the forward Section 42, a 2m enlargement of the overwing Section 44, and a 2.7m stretch of the aft Section 46. Overall total body stretch is 9.2m.
The vertical and horizontal tail surfaces are enlarged to ensure adequate lateral stability control in cruise, as well as to improve directional control during landing and take-off. Boeing is to add tip extensions designed for the 747SP, as well as a larger chord rudder.
As a result of the revised performance of the 777-300X, that will equate to that of the 747-400, the plan for an increased revenue payload, or longer range 747-400X, appears to be attracting less interest. The strengthening needed for the -400X would provide a step towards the -400X Stretch, says Boeing. Operating cost difference between the -400 and the -400X Stretch "result in an improvement of 10% or more" in airline conditions, says Ozimek.
Source: Flight International
