Spherical Bearing with Tapered Hourglass Rolling Elements for Planetary Reduction Stage Applications

When a power gearbox for aerospace applications loses the lubricant, gears and bearings quickly become powerful heat sources capable of damaging internal components up to compromise the functionality of the system and, potentially, to jeopardize safety of flight. In the last years, helicopter manufacturers worldwide have developed several strategies to overcome the risk associated to the loss of lubrication condition, with the aim of making their drive systems able to operate as much as possible under these extreme conditions. Leonardo Helicopter Division (LHD) is part of this engineering challenge, in this paper an innovative bearing architecture for planetary reduction stages is presented. In this solution, the standard spherical bearings used to compensate misalignment of the pins are replaced with novel spherical bearings with tapered hourglass rolling elements that optimizes the internal kinematic of the bearing and reduces internal power losses; the main advantage is expected in operation without lubricating oil. This paper is a review step by step of the Technology Readiness Level of the solution, it contains: The next step will be the validation of the technology through comparative laboratory tests (TRL4).