Accomplishments of the Abrupt-Wing-Stall Program

Abstract

The Abrupt-Wing-Stall (AWS) Program has addressed the problem of uncommanded lateral motions, such as wing drop and wing rock, at transonic speeds. The genesis of this program was the experience of the F/A-18E/F program in the late 1990s, when wing drop was discovered in the heart of the maneuver envelope for the preproduction aircraft. Although the F/A-18E/F problem was subsequently corrected by a leading-edge flap scheduling change and the addition of a porous door to the wing fold fairing, the AWS program was initiated as a national response to the lack of technology readiness at the time of the F/A-18E/F development program. The AWS program objectives were to define causal factors for the F/A-18E/F experience, to gain insights into the flow physics associated with wing drop, and to develop methods and analytical tools so that future programs could identify this type of problem before going to flight test. The major goals of the AWS Program, the status of the technology before the program began, the program objectives, the accomplishments, and the impacts are reviewed. Lessons learned are presented for the benefit of programs that must assess whether a future vehicle will have uncommanded lateral motions before going to flight test.