Present-day trends toward flight at high speeds and high altitudes have led to increasing interest in the flutter speed at low densities and high Mach numbers. An experimental investigation has consequently been made to determine some of the effects of these parameters on flutter speed.

The compressive buckling stress of outstanding flanges reinforced by bulbs was computed by the strain-energy method for flanges having 10 shapes and a range of lengths. The results were checked for some cases by computations based on a differential-quation method. The edge of the flange opposite the bulb was considered clamped, and the loaded ends were considered simply supported.