Flight tests of large blended winglets on a Boeing 747-200 have shown fuel savings of about 6-7%, says Aviation Partners Boeing (APB) president Joe Clark.

"We expect to have the performance numbers for that in 60 days," adds Clark, who says a further phase of proof-of-concept flight testing is planned later this year. The 4.42m (14ft 6in) high winglets are two and a half times the size of earlier versions used on the 747-400. The blended winglets improve the efficiency of the wing and cut drag by reducing the onset and size of wingtip vortices.

APB plans to offer the winglets for retrofit on 747-200s and even -400s if the tests are successful. Clark says the evaluation aims to prove that the winglets can be added to wingtips without needing extensive structural strengthening of the outboard wing. "Preliminary data indicates it is going to be a successful programme," he adds.

Release of the initial 747 test results came as Hapag-Lloyd and Air Berlin formally confirmed plans to have the blended winglet design retrofitted to their fleets of Next Generation 737-800 aircraft. Hapag-Lloyd will fit 26 kits, and Air Berlin has ordered 19. Others already signed up for conversion include GATX, Flightlease and South African Airways. Lauda Air and Transavia have also "expressed strong interest", says Clark.

He also reveals that APB plans to certificate the smaller 2.5m tall versions of the winglets on the 737-700 in the first quarter of 2001. Although Boeing originally believed that only the -800/900 versions with strengthened wings would be fitted with the winglets, recent analysis has proved that the -700 wing is also suitable for them.

This discovery could increase the potential market for retrofit and forward fit. Certification on the -800 is planned for January.

Source: Flight International