ProkhoroVj Tveshchevsky ,and Volkov 



surface and transported together with the model. The aerodynamic 

 forces to be excluded are determined as the difference between 

 the results of the measurements carried out over the board both 

 underway and at a speed equal to zero in flight. 



The specific behaviour of the ACV with a flexible skirt makes 

 difficult in some cases the use of traditional methods in calculating 

 the maneuvering qualities, dynamic stability and so on in terms of 

 the solution of equations of motion. The complexity and considerable 

 amount of tests necessary for defining the coefficients of the equa- 

 tions makes one use other methods of study. The determination of 

 transfer function's according to the required parameters in terms of 

 the experimentally defined frequency characteristics is considered to 

 be reasonable. These functions make it possible, as is known, to cal- 

 culate normal maneuvers of the object according to linear theory. 

 Besides it is important to have the possibility of directly evaluating 

 the behaviour of models in certain conditions, specifically, in dama- 

 ge situations. The tests with the both aims in view are carried out on 

 the experimental plant making it possible to simulate, in the main, 

 the conditions of the model free movement and in some cases to eli- 

 minate the necessity of carrying out the expensive tests with self- 

 propelled models. 



The basic diagram of the plant is shown in figure 12. During 

 the tests the model is towed along the towing tank; it displays five de- 

 grees of freedom, i. e. vertical emergence, side displacement, hee- 

 ling, yawing and trimming angles; all the kinematic parameters are 

 recorded. In case of side displacement the model is relieved of iner- 

 tia and friction forces in movable units of the plant by means of a 

 special servo- system. The significant element of the plant is the sys- 

 tem bringing the towing force into coincidence with the model centre 

 line irrespective of the position of model relative to the tank axis. 

 Finally, in case it is difficult to arrange the drives of controls on the 

 model, the electric systems are provided for the plant which are ca- 

 pable to imitate the action of the controls, particularly, side force 

 controls, by prescribing the side force, yawing moment and heeling 

 moment in accordance with the required law. 



Some test data obtained on the plant described are given be- 

 low. The studies were carried out on the ACV schematized model 

 N° 2 for the purpose of evaluating its course stability (with vertical 

 stabilizers mounted) and checking its other dynamic characteristics. 

 Figure 13 shows the relationship between the amplitude frequency 

 characteristic of the model for yawing angle at different speeds. It 



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