Overview of the abrupt wing stall program

Abstract

The abrupt wing stall (AWS) program was a 5-year program that addressed the problem of uncommanded, transonic lateral motions, such as wing drop, with experimental, computational, and simulation tools. A brief background is presented as are the motivations and objectives for the AWS program. Since the wing drop discovered in preproduction flight testing for the F/A-18E/F program was the immediate impetus for the AWS project, and since extensive flight data had been gathered, the preproduction F/A-18E configuration was utilized to examine the ability of current computational and wind-tunnel tools to predict such phenomena prior to flight. The scope included both steady and unsteady flow field studies for transonic flight conditions. The AWS program also adapted and assessed a free-to-roll (FTR) wind-tunnel testing technique traditionally used for low-speed studies of lateral dynamic stability for the transonic flow regime. This transonic FTR capability was demonstrated first in a proof-of-concept study and then applied to an investigation of four different aircraft configurations—two that were susceptible to wing drop, the preproduction F/A-18E and the AV-8B, and two that were not, the F/A-18C and the F-16C. Design insights have also been obtained from computational studies of these four aircraft configurations and from computations quantifying the impact of the various geometric wing differences between the F/A-18C and the F/A-18E. Finally, guidance is provided for assessing, in the simulator, the relative impact of experimentally determined lateral aerodynamic data on flight characteristics before going to flight test.