Fine Filtration - An Attractive Route Towards Lower Helicopter Operating Costs,

Helicopter transmission Times Between Overhaul TBOs appear to be surprisingly low, but cost analyses suggest that if the bulk of tribological problems could be eliminated, reductions in annual helicopter ownership costs would improve. In short, the main key to lower costs lies in improved mechanical reliability. Research and trials experience suggest that, provided a gearbox is free from design deficiencies, replacement of a gas turbine oil by a suitable gear oil combined with 3 microns absolute filtration would result in appreciably higher TBOs and enhanced reliability. This paper describes the research and trials experience that led to the adoption of fine filtration. However, to be fully effective it is imperative that the gearbox starts off life in the cleanest possible condition. To achieve this means revising standard production methods. TBOs could be phased out within the foreseable future and gearboxes fall into the Fit and Forget category where they belong.