Blade Load Reconstruction from Embedded Strain Measurements

Rotorcraft blades are subject to significant dynamic loads both in standard and critical operating conditions. The knowledge and the prediction of the produced aerodynamic loads could represent an advantage in preventing failures on the rotorcraft, but also to avoid unnecessary inspections and reduce the downtime of the aircraft. This work applies the Kálmán filtering technique to estimate the aerodynamic loads on a helicopter rotor blade at wind-tunnel model scale, representative of that of a medium-weight helicopter (900 mm span and 72.5 mm chord, corresponding to a 1:5-1:8 model scale). The loads estimation is based on strain measurements provided by Fibre Bragg Grating sensors embedded in the blade at several spanwise sections. Two different test campaigns have been done: a static one to characterize the experimental set-up followed by a wind-tunnel test campaign. The results show that the Fiber Bragg Grating sensors could represent an alternative choice with respect to strain gauges for strain measurements in in-flight health monitoring.