Computational Thermal Analysis and Testing to Improve Loss of Lubrication Performance of Helicopter Transmissions

The subject of the research in this paper is to achieve longer and more reliable loss of lubrication (LoL) performance. The research developed the computational thermal analysis model including airflow inside and outside transmissions to predict thermal behavior under LoL. And the research conducted the LoL performance test using the modified BK117D2 (EC145T2) main transmission optimally designed with the computational analysis. Data measurement during the test included temperatures of rotating components such as gears and bearings, temperature distribution on the gear teeth, and airflow speeds and heat fluxes around the transmission in order to analysis the test result. The test procedure was according to the EASA new rule, which has severer test condition than the past rule. The test result shows longer LoL performance than the past test of the BK117D2 main transmission. And the computational analysis model was validated with the measured data. Then, the failure cause and possible future improvements were investigated based on the measured data and the analysis model. Finally the research concluded the modifications on the transmission, the computational analysis model and the measured data are able to make LoL performance longer and more reliable.