An analysis has been performed of experimental results obtained in rol
l oscillation tests at 30-deg angle of attack of a 65-deg sharp-edged
delta wing in order to uncover the fluid mechanical phenomena causing
the unusual, highly nonlinear vehicle dynamics. In addition to the exp
ected effect of convective now time lag, the test results show highly
nonlinear effects of the angular rate, which themselves are influenced
by the effect of convective time lag. A flow hypothesis is presented
that can explain the unusual experimental results.