Modelling and finite element analysis of a complex helicopter transmission including housing, shafts, and gears

The availability of very fast computers and the extensive use of 3 dimensional geometric modelling allow the solution of very complex shapes using the Finite Element Modelling technique. As the calculation of Helicopter Transmission housing and gear deflection and stress is influenced by several interacting effects, Finite Element Analysis should include housings, shafts, bearings and gears. The actual main case design of the EH101 Transmission has been studied using integrated Computer Aided Design and Finite Element modelling and analysis. The EH101 Helicopter has a three engine, four reduction stage 5200 HP Transmission with a reduction rate of about 100. The main case design including the II/III stage reduction gears has been first analysed. The activity covered the generation of the complex geometric CAD shape using CATIA exact solid modelling and the generation of the Finite Element model of the housing. The mathematical model has been completed with the introduction of shafts, gears and a simplified representation of bearing effects. Using the NASTRAN super-element approach, it has been possible to analyse separately each element and at the same time taking account of the interacting effects. Using this technique, the deflection and stress behaviour of housing, shafts, bearings and gears can be predicted in the same integrated analysis. This same technique was used to analyze the Ell 101 Main Gear Box Upper and Lower Cases.