DYNAMIC MODELING OF A HELICOPTER LUBRICATION SYSTEM

A dynamics model of a typical helicopter transmission lubrication system is presented. The computer fluid and structural model is shown to correctly simulate both mean pressures and also a troublesome self-excited pressure oscillation phenomenon seen in test. The math model incorporates 1st order bulk modulus representations of the larger system volumes and nonlinear wave equation models for the various lubrication lines. Mechanical components, such as poppets, are modeled by 2nd order differential equations that include poppet-seat impact dynamics. The equation solutions are done by numerical integration of the equations of motion along with an inner loop one dimensional finite difference solution for each lubrication line of significant length. The model is effectively utilized to predict the efficacy of design changes intended to stabilize the chatter. Several of these design changes are discussed along with the corresponding test and simulation correlations. A novel test methodology useful for stability testing of fluid systems along with the corresponding stability results are presented.