A ULTRALIGHT AMPHIBIOUS PRANDTLPLANE: TOWING TANK TESTS ON A SCALED MODEL

The first part of the paper describes the design of a 1/3 scaled model of a new ultralight amphibian with a PrandtlPlane wing configuration, in order to conduct towing tank tests. The second part deals with the results of tests; different kinds of test have been performed in order to determine the behavior of the hull during the take off: "low speed tests", "high speed tests" and "stability tests". The results are the measured forces from the interactions between water and body and, also, the kinematics of the body during the runs at different speeds. During the test runs at the INSEAN-CNR plants in Rome, the aerodynamic forces and moments relevant to the test speeds have been applied by means of actuators, dumping rigs and springs properly designed. Two configurations have been tested, characterized by different positions of the step. The results show that the kinetic of the hull is in line with CFD calculation while higher errors can be found in the evaluation of the hydrodynamic drag. The dynamic stability of the aircraft results deeply dependent on the step position; instability phenomena are observed for the configuration having the step far from the center of gravity.