Andrew Doyle/LONDON
BOEING HAS INCREASED the range of its 747-600X and reduced the size of the -500X following consultations with its airline working group.
The revised configurations are now being offered as the baseline aircraft to potential customers. The move follows the US manufacturer's recent decision to switch to a fly-by-wire flight-control system (FCS) (Flight International, 31 July-6 August).
The -600X is to have a range of 14,340km (7,750nm) with 548 passengers in three classes, an increase of 460km over the initial proposal. The aircraft's maximum take-off weight will be 538,440kg, with maximum landing and zero-fuel weights of 383,630kg and 358,660kg, respectively.
The fuselage length of the -500X has been shortened by 3m, to 76m, yielding a range increase from 15,080km to 16,100km. Passenger capacity is reduced from 487 to 462. Both derivatives of the aircraft will have wingspans of 76.6m, no winglets, and slats instead of flaps on the leading edge.
Major changes have been made to the undercarriage, to cope with the higher weights. Both aircraft will have six-wheel bogies on two wing-mounted posts and four-wheel bogies on two fuselage-mounted posts, for a total of 20 main wheels. All four main posts will be steerable, and the nose gear will have four, parallel wheels. Approach speed has been reduced by 7kt (13km/h), to stop an increase in the landing roll at maximum landing weight, compared with the 747-400. Avionics architecture will be based on that of the 777.
The -500X/600X will have three hydraulic systems instead of the -400's four, because of space constraints in the outboard-engine pylons. Left and right hydraulic systems will be driven by the inboard engines only, and will power the FCS. A centre system will be bleed-air driven and power the undercarriage, brakes and flaps. A ram-air turbine will be installed, to satisfy certification requirements on back-up power sources.
Meanwhile, engine manufacturers are close to finalising the configurations of the powerplants they will offer. Boeing requires a target thrust of 343kN (77,000lb), with growth potential to 356kN.
Rolls-Royce's Trent 900 will have the 2.8m-diameter fan and combustor of the Trent 895, with scaled-down 895 intermediate (IP) and high-pressure (HP) compressors, a new five-stage low-pressure (LP) turbine, and "reduced-loading" IP and HP turbines. The nacelle will be a "slim-line" version of that used on the 777.
The joint venture formed by General Electric and Pratt & Whitney plans to offer an engine with a 2.75m-diameter fan, although a decision on whether to switch to a 2.8m fan is likely to be taken by the end of the month.
GE is to supply the HP compressor, combustor and HP turbine, while P&W will be responsible for supplying the fan, LP compressor and LP turbine.
Source: Flight International
