Qantas has asked Boeing to build and certify its three newly ordered 747-400s to an increased-gross-weight (IGW) specification, to allow the Australian carrier to overcome payload-range restrictions to Europe and the USA.
It is pressing the Seattle-based manufacturer to commit to a -400 growth derivative, with a maximum take-off weight (MTOW) of just over 413,000kg. While Boeing has not been contracted to produce a heavier 747 version, it is understood that Qantas is viewed as a "back-door" approach to launching a new longer-range, heavier version, at a time when the company's board is preoccupied with production hold-ups and the consequences of its merger with McDonnell Douglas.
Qantas needs the extra weight margin to carry additional fuel and a full payload all-year round from Los Angeles to Sydney, and from Singapore to London. Under hot conditions, the airline is forced to leave as many as 30 seats empty and is limited on cargo. It is also in the process of installing an extra 2,720kg of new in-flight entertainment equipment to each aircraft.
The new IGW being discussed by Qantas is thought to represent an interim step to developing new derivatives using a "modular approach". The -400IGW, similar to the proposed extended-range 747-200X (Flight International, 5-11 November), would incorporate a strengthened 747-400 Freighter wing, offering progressively higher MTOWs from the existing 397,250kg, through 400,880kg to just over 413,000kg.
Reconciling this last growth step with Qantas' three contracted delivery dates of October and November 1999 and March 2000 could pose a problem. The aircraft will require a heavier landing gear and it is doubtful that new wheels and brakes would be ready in time. One suggested solution is to produce the three 747s to the IGW standard, but operate at the existing -400 MTOW until new gear could be retrofitted and the aircraft re-certificated to the higher weight.
The redesigned gear and structure developed to support the last growth step would then provide the platform for the next phase, now dubbed the -400X. This entails growth to 426,300kg and range increase to 15,200km (8,200nm). The same wing, undercarriage and centrebody improvements would also form the basis of a model with a 485-seat stretch and the range of a -400.
Qantas is expected to issue an request for tenders to competing engine manufacturers for powerplants by December.
Rolls-Royce is expected to offer its improved RB.211-524G/HT engine as a new build powerplant and a retrofit for the carrier's 18 -524G equipped -400s. General Electric will offer the CF6-80C2, stressing commonality with Qantas' Boeing 767-300 fleet, while Pratt & Whitney is likely to propose its PW4056.
Source: Flight International
