USAGE AND STRUCTURAL LIFE MONITORING WITH HUMS

This paper presents the results of a study that evaluated the effectiveness of usage monitoring for determining fatigue damage exposure on life-limited components and to assess potential benefits to the operator. Usage data, collected on a Bell Model 412 helicopter that was equipped with a commercially available Health and Usage Monitoring System (HUMS) and operated by Petroleum Helicopters Inc. (PHI) under an independent flight trial program, was used to evaluate two usage monitoring techniques, flight condition recognition (FCR) and flight load synthesis (FLS). For the selected components that were analyzed, the results of the evaluation indicated a potential for extending retirement lives. This was due to the damage accumulation rate for the FCR and FLS techniques being slower (“slow clock”) than the current method of using actual flight hours as the basis for retirement times. Based on the mission flown for this aircraft, which is transporting workcrews to offshore oil platforms, the flight hours charged against retirement times could be reduced by 50% or greater. Thus the operator would gain a considerable payback in reduced maintenance costs due to extension of retirement intervals.