Flutter of forward swept wings, analyses and tests

Abstract

This report reveals information relating to flutter research with military implications to aircraft design. Since the safeguarding of this information is necessary in the interests of national security, this report, exception the title, has been classified "Confidential" in its entirety in accordance with paragraphs 2.s and 24.a(9) of AFR 205-1. WADC TR 53-161, Part 2 54WCLSA-416 ULNCLASSIFIED) ABSTRACT A wind tunnel model was designed, constructed, and tested in order to accumulate experimental data on the effects of systematic changes of various tip pod mass parameters and of rigid body degrees of freedom on wing flutter characteristics, and to compare these data with the results of theoretical analyses. A tapered wing with quarter chord swept back 400 was tested with heavy tip pods in cantilever, symmetric, and antisymmetric configurations. Flutter analyses were made of two selected configurations in each of the cantilever, symmetric, and antisymmetric modes. Computed results from analyses based on strip theory aerodynamics, with one exception, gave good agreement with experimental results, whereas analyses based on finite wing aerodynamics in general yielded appreciably unconservative flutter speeds.

Parametric aeroelastic stability analysis of a generic X-wing aircraft

“…This symmetric, low-frequency flutter condition is commonly referred to as "body-freedom" flutter and is a coupling of wing bending and rigid-body pitch and plunge motions. 3 Because of the similarities between this configuration and the X-wing in a fixed rotor mode, it is likely that such an instability will be characteristic of the vehicle.…”

“…One study involved flutter of the X-29 forward-swept wing aircraft, 3 and the other involved flutter of a tailless sailplane. 14 As another point of interest, the addition of a tail would probably increase nosedown pitching moment and therefore would shift the dynamic divergence curve to the right as shown in Fig.…”

Quadratic synthhesis of integrated active controls for an aeroelastic forward-swept-wing aircraft

“…Recent studies by Miller et al 3 and Weisshaar et al 4 ' 5 have shown that the critical mode of instability for a forwardswept-wing aircraft is not likely to be wing divergence. Instead the loss of aeroelastic stiffness of the swept-forward wing that occurs at high speeds leads to increased cross coupling between flight mechanics modes and flexible modes of the structure.…”