EXPERIMENTAL RESEARCH ON HELICOPTER TAIL SHAKE PHENOMENON

Helicopter tail shake phenomenon is still remained as a long dragged issue that adversely affected the overall performance, occupants ’ comfort and handling qualities of helicopter. The objective of this research is to improve basic understanding of the viscous unsteady flow phenomenon observed behind the helicopter tail part. For this, a wind tunnel test had been conducted with a rigid 14 % generic model of Eurocopter 350Z helicopter in the Universiti Teknologi Malaysia- Low Speed Tunnel (UTM-LST) with a test section size of 2m x 1.5m x 5.8m and 288 km/hr maximum test wind speed. The model, supplied by Eurocopter France, is equipped with a motor that can rotate the main rotor up to 900 rpm during wind-on condition. As the induced wake, which consequently causing tail to shake, differs with angle of attack and yaw angle, the wind tunnel test was performed in a range angle of-10o to +10o, respectively. The selected test wind speed was 40 m/s, which corresponds to a Reynolds number of 3.7 x 106. To investigate the characteristics of the induced wake, velocity fluctuation mapping using hotwire was done at 3 different planes behind the model with each plane consists of 4 measurement points. Results obtained later depict some interesting facts of this wake phenomenon