Metodo sperimentale sul Take-off di un Idrovolante: Rimorchio e Stabilità Longitudinale su IDINTOS

An experimental Towing-tank method for testing a seaplane was developed and implemented. The defined test programme represents a complete experimental task for study the hydrodynamic characteristics of the flying boat during take-off are. A specific test-rig was designed, and then developed during the test, by CNR-INSEAN in collaboration with the customer EDI, who took care of its development and implementation. In particular various simulators of the aerodynamic components of the aircraft were designed because wings and control planes were not modelled. In the Low Speed Tests the model was "free to trim", whereas in the High Speed Tests it was restrained from pitching, i.e. runs were performed at a fixed trim. Free to trim characteristics of the seaplane were determined below hump, while resistance and pitching moment characteristics in the planing region were plotted in contours maps up to the take-off. The Longitudinal Stability measurements characterize the stability limits of the flying boat during take-off. The tests were performed in the high speed region, from hump to take-off, with the "free to trim" model. When oscillations occured, the measured damping moment M was combined with the calculated angular velocity in pitch "q", providing the pitch damping moment rate dM/dq. The trim values corresponding to the porpoising limits were plotted on the performance contours maps, and this completes the hydrodynamic characteristics of the seaplane during the take-off.