REALIZATION OF A CONTINUOUS BALANCE TESTING PROCEDURE IN A COMPRESSOR-DRIVEN TRANSONIC WIND TUNNEL V.V. Petronevich, Yu.V. Kartashev, A.R. Gorbushin, K.D. Bukharov Central Aerohydrodynamic Institute (TsAGI), Zhukovsky, Moscow Region, 140181, Russia Key words: compressor-driven transonic wind tunnel, Mach number control system, continuous tests method, model pitch angle Abstract The ways of efficiency and information density of the experimental research in transonic wind tunnels increase are revised; in particular, op- timization of the wind tunnel control systems for realization of the continuous balance testing mode is described. The problem of the Mach number stabilization in the test section of a large transonic compressor-driven wind tunnel at subsonic flow conditions with continuous air- craft model pitch angle variation based on an example of TsAGI T-128 wind tunnel is solved by implementing an additional adjusting con- trolling impact on the base of the forecast of Mach number disturbances caused by the model pitch angle variation to the control system. Ex- amples of the system practical realization are given. Settings of T-128 wind tunnel Data Acqui- sition and Control System (DACS) measurement channels’ filters are optimized. It minimizes sig- nals’ dynamic deviations and, at the same time, provides noise suppress within main frequency range. Evaluation of pitch/pause and continu- ous balance modes convergence in T-128 wind tunnel (Mach number M=0.4) for two pitch an- gle variation rates of aircraft model is given. 1 Introduction Increasing efficiency and information density of the experimental research while testing aircraft models is an actual problem, especially for high-power industrial wind tunnels (WT). One of the ways of solving this problem together with complex automation of the aircraft model testing is development and implementation of the continuous test method. Continuous test method means continuous change of the parameter under control (Mach number, aircraft model’s pitch or slip angles, etc.) with simultaneous continuous measure- ment of the researched parameters (forces, mo- ments, angles, flow parameters, etc.). Usage of the continuous test method allows reducing the test time by several times comparing with the pitch/pause (traditional) test mode during which measurement is performed at steady values of the parameters under control and, correspond- ingly, it allows reducing power expenses on tests. While performing tests by the continuous method the problem of Mach number stabiliza- tion in the wind tunnel test section with a defi- nite accuracy (about ±0.001) with continuous variation of the angular position of the aircraft model appears. This is an important condition of performing balance tests as aerodynamic coeffi- cients considerably depend on Mach number, especially close to its sonic value [1]. As a rule, Mach number control systems are created for pitch/pause test mode. This method implies stepped changing of the model position and does not provide the needed accu- 1