GUY NORRIS / LOS ANGELES
7E7 engines hold key to Advanced freighter and passenger versions under study
Boeing is studying different-sized stretches for the passenger and freighter versions of its proposed 747 "Advanced" and, based on the availability of 7E7 technology, is expected to offer the new family for possible entry-into-service in 2009.
Fresh details of the study, revealed by Boeing Commercial Aviation Services as part of a briefing on airport compatibility, show that the maximum take-off weight (MTOW) of the stretched freighter version could be around 435,450kg (960,000lb). This is nearly 22,500kg heavier than the 747-400ERF which, with an MTOW of 413,000kg, is the heaviest 747. The Advanced freighter would offer a payload increase of around 18t over the -400ERF.
The freighter would also be the longest of the two proposed stretches, with fuselage extensions forward and aft of the wingbox to increase overall length by almost 5.1m (16.7ft) to around 75.8m. The passenger version, with a 3.5m stretch, would increase to an overall length of 74.2m. Other than the normal differences between the standard passenger and freighter variants, the two models would also share 777-300ER-style raked wingtips and the trailing edge wedge aerodynamic improvement developed for the MD-11 and already flight tested on a 747.
Key to both, however, is the use of new 7E7 engines, the overall efficiency improvements of which have made the entire 747 Advanced studies possible. Combined with changes already outlined for the former -400XQLR study, the use of 7E7 technology is expected to give the 747 the best, and possibly last, chance to be stretched and to continue in production into the next decade. Boeing says improvements in noise, fuel burn and operating costs will be accompanied by a faster cruise speed of Mach 0.86.
Part of the improvement will come from the raked wingtips and a resulting increase in wing span to 68.7m, or almost 4m larger than the current versions. Despite the planned span increase and changes to the wing root area, the basic wheel track width retains the current dimensions, while turning radius for the larger freighter stretch will be similar to 777-300.
Boeing says the Advanced is "certainly a different product from other 747 derivatives that have been offered", but "nothing is yet defined. It will come after the 7E7."
Exploratory talks with several key 747 operators, believed to include Cathay Pacific, Lufthansa, Qantas and Singapore Airlines, have "just been getting under way", it adds.
Boeing has issued its first public warning that it is considering the closure of its 757 programme as a result of collapse in demand. Speaking after the release of second quarter results last week, chief executive Phil Condit said that no decision has been taken, but with production running at a rate of one a month he wanted to warn the market that the termination of the programme is a possibility. Boeing says it could incur a $200 million one-time charge if it closed production.Source: Flight International
