Boeing has begun flight tests of a trailing-edge wedge wing modification on a 747-400 as the first element of a potential package of changes that could be applied to future 747 derivatives.

The modification consists of a triangular-shaped wedge on the lower surface of the wing trailing edge, and is based on the aerodynamic change developed by McDonnell Douglas to help recover the performance of the MD-11 tri-jet airliner.

The wedge, which extends over 2.5% of wing's chord, is believed to be added to all surfaces, including the ailerons. The flight tests, which began in late October, follow successful windtunnel evaluations which suggest potential lift/drag improvements of 3-4% (Flight International, 16-22 September).

"We should know within a week whether it is something that gives us an aerodynamic benefit," says Boeing Commercial Airplanes chief engineer of aerodynamics, Bob Kelley-Wickemeyer.

"Assuming that the benefits are sufficiently large we will need to collect additional data and try to figure out the best way to exploit it," he adds.

Tests will include nautical air miles/lb fuel, or NAMS, tests, as well as initial buffet trials.

Source: Flight International