Envelope bearing analysis: Theory and practice

The rolling element bearing is an important element for power transmission within the helicopter drive train system. Monitoring the condition of the rolling bearing element's component provides advantages in the operation, safety, and maintenance areas. An overview of the diagnostic process for a rolling element bearing with pit type fault from the mechanical defect, to the defect signature, to the detection process is presented. The detection process applies the enveloping technique. The work presented is demonstrated with an analytical description of the enveloping process, analytical examples, a simple numerical simulation and the results from an operational helicopter. The benefits of understanding the fundamental bearing analysis technology include improved diagnostics capability and prognostic capability.