Analysis of vibroacoustic properties of the 250-C20R/2 RRC (Allison) engine in the support surface of the compressor

The paper presents an analysis of the levels of vibration on the compressor in the support surface of the American RRC Allison 250-C20R engine built into the SW-4 Puszczyk helicopter. Then, it presents the association of occurring vibrations with their source of origin, and also the comparison of their values with the limit values specified in the operating manual of the helicopter. The methodology of the conducted research and analyses are explained. The essential elements preceding the research, such as determining time courses, on the basis of which the most important parts to conduct the detailed analyses of changes of the basic parameters and compliance with technical conditions, are defined. Moreover, the theoretical issues in terms of determination and description of the characteristic parameters of mechanical vibrations are briefly presented. The typical terms used in the procedures of vibration, description and measurements are explained. The importance of the interpretation of measurements is quite significantly emphasised and the components of the main engine, which were subject to measurement, are indicated. The difficulties in the identification of the vibration due to the high probability of overlapping of vibrations coming from several elements are emphasised. Next, the methodology of measurement is described, in which, among others, mounting points of vibration sensors are presented. The final part of the paper is mainly a graphical presentation of the results, on the basis of which the conclusions are developed. The conclusions show a lack of decisive symptoms indicating the danger at the level of vibrations, and present the future directions of work, which will allow for a more detailed analysis.