Boeing has added growth-weight and "simple-stretch" derivatives of its 747-400 to product-development plans, following its decision to shelve work on the 747-500X and -600X.
An initial version, which is called the 747-400 increased-gross-weight (IGW), would offer a modest increase in range, compared with the existing -400. This could be followed by a slightly stretched version capable of accommodating 60-80 extra passengers, although this model would have significantly less range than that of the -400.
The 747-400IGWand stretch are based on studies postponed around two years ago after Boeing decided to pursue the more radical -500X/600X derivatives, which were expected to cost $7 billion to develop. The 747-400IGW and stretch would offer relatively small performance improvements, but would be cheap to develop as a stop-gap measure while the company studies a possible all-new design for the large-aircraft market.
The -400IGWwould be likely to offer 740km (400nm) in additional range, to 14,060km, with maximum take-off weight increasing to around 418t, from the -400's 397t. The stretch would also have a higher take-off weight, but would suffer a range penalty of around 1,660km, compared with that of the -400IGW, to 12,400km.
According to one senior airline executive, "-the key to all of this is an available powerplant". The IGW aircraft will need an engine in the 280-285kN (63-64,000lb)-thrust range, and a simple throttle-push of engines now available on the 747 is not thought feasible.
The additional fuel for the IGW aircraft is likely to be accommodated in an enlarged centre-wingbox tank, where there is already available space. The IGW would have particular appeal for transpacific 747-400 operations which, at certain times of the year, are facing payload/range restrictions. Cathay Pacific's New York run, for example, has to stop in Vancouver. Cathay, however, suggests that these problems could be overcome by using more efficient routes.
While the stretched aircraft has a range penalty, South-East Asian carriers are interested in extra capacity for regional routes to Australia and Japan. The stretch also has appeal for Japanese carriers which use 747s domestically, but which face airport congestion.
Source: Flight International
