The flutter of swept and unswept wings with fixed-root conditions Part 1 wind-tunnel experiments Part 2 comparison of experiment and theory Part 3 wing torsional stiffness criterion

Abstract

The 'fixed-root' flexure-torsion flutter characteristics of four model wings of different taper ratios have been investigated in the wind tunnel. The wing inertia axis and the angle of sweepback have been varied on each wing over the ranges 0.4c to 0.5c and 0 deg to 50 deg respectively. The results show that :- (i) The flutter speed at any angle of sweepback (including the unswept case) varies approximately linearly with inertia axis position increasing as the inertia axis is moved forward aud approximately linearly with wing taper ratio increasing as the taper is increased. (ii) The flutter speed decreases slightly for small angles of sweepback and then increases rapidly as sweepback increases. The results of one theoretical treatment gave good agreement with experiment for variation of flutter speed with sweepback and inertia axis. The experimental results support the present wing torsional stiffness criterion. Simple amendment to the criterion are put forward for the effects of sweepback.