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The UF-XS Japanese STOL Seaplane was evaluated to determine the flying qualities in configurations PA, L, and TO at approach speeds in the vicinity of 55 kt and the hydrodynamic characteristics while on the water. The NASA Ames simulator showed good correlation with the airplane's aerodynamic characteristics. The airplane has neutral to unstable static longitudinal stability, weak directional stability, large adverse yaw, a long period moderately damped Dutch Roll mode, a divergent spiral mode, and trims for flight in a 130 left sideslip. An automatic stabilization equipment (ASE) makes the static longitudinal stability and sgiral modes positive but does not improve the remaining items. Takeoff and landing touchdown speed is 50 k T-ai~ipane has a hydrodynamic stable ele.ator range of 20 to 35 degrees up elevator. A "digging in" and slight "po.poising" tendency is exhibited at elevator positions less than 200. The airplane possesses good spray characteristics. The mission capability of a STOL seaplane should areatly improve with reduction in takeoff and landing speed; however, evalu;tion of the airplane at lower speeds was not possible due to several airplane limitations. Monitoring of the Japanese STOL seaplane program should be contLnued and a reevaluation performed after required improvements have been accomplished.

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