Oil flows inside a single-stage jet-lubricated mechanical transmission with spur gears

Besides ensuring physical separation between contact surfaces and removing the heat, lubrication oil in helicopter (MGB)s is also used to convey any metallic debris to instrumentation capable of providing indications on the health status of the MGB itself. Accurate knowledge of the actual oil flow patterns, not only of its main directions, and of the parameters that may influence them is required for this mechanism to function properly. A new test rig is proposed here, designed to provide insight of the oil flows inside a jet-lubricated test gearbox with a quantitative approach rather than a qualitative one. An extensive test campaign has been conducted on this test rig, and the results are reported here. Subsequently, these results are discussed to highlight the factors that most influence the behaviour of the lubricant oil flow after the jet impingement on the flanks.