  This paper explores the fluid-elastic response of a cantilevered flexible
sheet in the presence of uniform airflow. The leading edge of the sheet is
clamped, while at the trailing edge, in-plane tension is applied to provide
additional rigidity to the sheet's small but finite bending stiffness. We
outline a series of experiments performed in a wind tunnel with the purpose of
examining fluid-elastic instabilities. In particular, we examine the role of
in-plane tension induced rigidity and how it influences static divergence and
convected wave instabilities. The flow is characterised by Reynolds numbers of
order $10^5$-$10^6$ and we specifically examine a sheet with an aspect ratio of
$L/l=1.33$. A unique aspect of this present work, is the direct measurement of
the sheet's three-dimensional displacement through an optical tracking method
with a grid of passive markers placed on the sheet surface. We show the
evolution of the sheet surface from stability, through to divergence, and then
finally into flutter. The frequency composition of the flutter event shows
higher harmonic components that suggest significant nonlinearities. Tension
induced rigidity plays a crucial role in the response of the sheet to the fluid
in both postponing and suppressing instabilities.
