Blade Deformation measurements with IPCT on an EC135 helicopter rotor

Kurzfassung

For the design of a helicopter rotor blade, it is crucial to predict the dynamic behaviour and occurring forces and moments. For the validation of prediction tools, reliable flight test data are required. Furthermore, flight test measurements are necessary for the calculation of fatigue loads. Today, strain gauges are applied to a helicopter rotor blade to perform measurements in flight test. Locally, they allow a precise strain measurement for the complete rotor revolution. The instrumentation implies a high effort. Furthermore, wiring can imply difficulties due to its weight and its perturbation of the aerodynamic shape. An optical measurement technique may overcome some of the limitations of strain gauges. A precise measurement of the deformation of the complete surface of the rotor blade allows to locate high strains and to identify oscillatory modes. The exact blade position can be identified optically. One of these advanced optical measurement techniques is the Image Pattern Correlation Technique (IPCT). Today, IPCT is a state of the art measurement technique for static and dynamic deformations. In AIM, DLR and Eurocopter explore the feasibility of Quantitative Video Technique (QVT) together with the Image Pattern Correlation Technique (IPCT) on the rotating main rotor blades of a flying helicopter.