Boeing has acknowledged that sticking to the 747-8 Freighter programme's original schedule could mean that the aircraft is delivered slightly above nominal weight targets.
"We're a little heavier than I'd like us to be," says Ross Bogue, Boeing 747-8 vice-president and general manager.
The first aircraft, which is scheduled for delivery in early April 2009, is slightly less than 1% above its weight target, he adds. Boeing lists the maximum zero fuel weight for the 747-8F as 321,600kg (709,000lb), meaning that even a 1% difference could exceed 3t.
Part of the weight problem is caused by Boeing's decision to keep deliveries for the 747-8 on schedule, Bogue says. If deliveries were delayed, Boeing's engineers would have more time to optimise the design of the aircraft to reduce weight. However, Boeing remains committed to the original schedule, and the airframer still hopes to reduce the aircraft weight to nominal targets before first delivery.
The 747-8 has faced schedule pressure since late last year. A supply chain breakdown that caused a delay of at least eight months for the 787 programme meant that engineers from that programme could not be transferred to work on the next-generation 747.
Boeing solved that problem by outsourcing engineering work to a variety of aerospace firms abroad, including companies in Russia and Spain. The engineering workforce at Boeing Integrated Defense Systems sites in St Louis, Missouri, and Long Beach, California, were also loaned to the programme.
Although this strategy helped to overcome the workforce shortfall for the 747-8F, Boeing has also learned that the work was distributed too broadly, Bogue says. "I would tell you we spread the work too far on the Freighter," he says.
As development work ramps up next year for the passenger 747-8 Intercontinental, Boeing will place a higher concentration of engineering work among a few number of suppliers, Bogue explains.