Structural health monitoring of rotating blades on helicopters

Abstract

The paper discusses the structural health monitoring of rotating blades on helicopters (RBH) based on the application of Modal Analysis. The study discussed in this paper includes the experimental validation of state-of-the-art techniques for the on-line measurement of dynamic signals of helicopter rotating units, optimization of the sensor type for rotating unit measurement, analysis of the practical applicability of modal analysis techniques for condition-based monitoring of rotating structures and estimation of the efficiency of the experimental system for the identification of practical damages of blades. The research was conducted using helicopter blade models operating within an experimental test bench. The capabilities of diagnostic technique application to main rotor gears and bearings are also presented. Conclusions are made about the successful analysis of the operational modal analysis technique applicability for the structural health monitoring of a rotating blade, and its effectiveness for damage identification. Two strategies of the RBH repair – with a continuously condition-based monitoring with the proposed technology and one without such monitoring, were discussed. The Markov chain reliability models for each strategy were analyzed and the reliability improvement factor for the proposed monitoring technology in comparison with a traditional one was evaluated. It is shown that the reliability improvement factor is more effective for the proposed method as compared to the traditional one.

Keyword : condition monitoring, rotating blades, vibration diagnostics, operational modal analysis, structural health monitoring