Boeing rejigs KC-767 modification, testing to meet schedule

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Boeing has moved modification work on KC-767 tankers for Italy and Japan from Aeronavali in Italy to its Wichita, Kansas plant in a bid to meet revised delivery schedules for the delay-hit programme.

Naples-based Aeronavali was to modify three of the four tankers for Japan, but now the aircraft will be converted in Wichita. In addition, two Italian KC-767s being modified by Aeronavali will now be flown to Wichita for the work to be completed, says Jeff Keller, Italian KC-767 programme manager.

Boeing has made the changes to meet revised schedules calling for delivery of the first two Japanese tankers in the first quarter of 2008 and the first two Italian aircraft by the end of the second quarter. Under the original schedule the first KC-767 was to be delivered to Italy in November 2005, with Japan to receive its first example in 2007.

Italy's first of four tankers flew in May 2005, with Japan's first of four having followed in December 2006. The KC-767 development delays have become an issue for Boeing in the competition for the $40 billion US Air Force KC-X tanker replacement programme, facing a rival bid by Northrop Grumman and EADS North America offering the Airbus A330-200-based KC-30.

A second Italian KC-767 will join the flight-test programme early next year to help complete certification and operability testing. Refuelling system testing will be focused on aircraft 2, while aircraft 1 will complete the airworthiness testing required for US Federal Aviation Administration supplemental type certification of the modifications.

Testing was delayed while Boeing developed a solution to high-speed buffeting caused by airflow separation on the wing pylons carrying the refuelling pods. Under FAA rules, maximum operating speed is set by the onset of buffet, and the pylon problem limited the KC-767 to a lower speed than that contractually guaranteed.

Buffeting has been eliminated by changing the area ruling of the pylon, by making the trailing-edge thicker to slow the airflow velocity, says Keller. "We have completed envelope expansion with the production pylon," he says, adding that results were better than predicted and "maximum operating speed is now on contract".

Boeing still has significant refuelling testing ahead of it, and acknowledges the schedule remains "aggressive". The hoses were extended during flights earlier this year, but receiver contacts and fuel transfers will not begin until early 2008. The choice of receiver aircraft for testing has still to be made, he says.

Testing of the Japanese KC-767, which only has the refuelling boom, has been delayed by additional work requested by the customer. The first aircraft returned to flight at the end of August after wiring and other upgrades.

The second tanker for Japan flew on 18 November after modification in Wichita. The third aircraft has completed final body join at Boeing's 767 final-assembly plant in Everett, Washington. The fourth Italian aircraft is in Wichita, but is still planned to be delivered to Aeronavali for modification, says Keller.