In this study, the design of the FL_SUP SGI TP001-31-001-01 head cover enables the observation of both the pressure and suction side cavitations in turbine mode thanks to its large viewing windows (SGI TP01 92-001-01). Users have a direct view of the region between the gate vane and the runner inner. Excellent pictures of the cavitations have been achieved by associating a high resolution camera with a lighting system. For cavitation at the runner suction side inner, 2 kinds of cavitation can be seen. A mapping of these cavitation limits was completed and Etasigma curves were performed at 2 operating points.