Three parallel plate assemblies were tested to investigate the flow induced deflections of the individual plates. Special strain gages imbedded in the edges of the plates were used to measure plate deflections at flow rates up to 190% of the theoretical collapse velocity. The results indicate that the flow induced deflection phenomenon is essentially a magnification of built-in channel spacing perturbations. The deflections assume a sine wave shape along the long axis of the channel, with the greatest deflections occurring at the inlet to the channels. Adjacent plates always move in opposite directions at high flow rates, alternately opening and closing coolant channels. Above the critical velocity, deflections were observed which were sufficient to cause adjacent plates to touch. At about 1.9 times the theoretical collapse velocity, a high frequency flutter of the instrumented plates was observed. Use of an inlet support comb eliminated this flutter.