FASTOP: A Flutter and Strength optimization Program for Lifting-Surface Structures

A new computer program entitled FASTOP is described, and results obtained from its application to the structural sizing of three lifting-surface structures for combined strength and flutter-speed requirements are presented. Two detailed finite-element models of metallic structures (having between 600 and 900 elements) and a preliminary-design representation of an advanced-composite wing are considered. Near-minimum-weight designs are achieved in only six combined strength and flutter resizing cycles for the two metallic structures, one of which includes mass-balance design variables. For the composite wing, FASTOP is used to resize the individual ply thicknesses of a strength-based design for increased flutter speed; the same excellent convergence characteristics are demonstrated.