Observers question whether the 747 orderbook is large enough to sustain production until flight tests and deliveries of the Advanced could start in 2007-9. The 747-400 order backlog stands at 43. This is steadily diminishing, with around three years of work remaining at current build rates.
It is unclear if those carriers that have yet to decide on a future large capacity aircraft will wait until 2009. The rival Airbus A380 is due to enter service in 2006 and competitive pressure will possibly force undecided carriers such as British Airways and Cathay Pacific Airways to make a decision sooner.
Questions hang over the proposed use of 7E7 engines for the Advanced. Boeing has opted for a no-bleed-air concept for the 7E7 in a move towards a more- electric aircraft. The 747, however, requires bleed air for a range of functions, including start-up, environmental control, hydraulics and anti-icing.
Industry sources suggest it will be difficult to use the same combination of core and fan while bleeding air.
Ground clearance issues on the 747 limit engine fan diameter to just over 2.6m (100in), but engine manufacturers are looking at 2.8-2.9m fans for the 7E7.
Source: Flight International
Seems would have to be fast and modify the 747 substantially ... difficult trade-off ...
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