Load Monitoring of Composite Aircraft Wing Using Fibre Bragg Grating Sensors

CSIR-NAL, Bangalore in collaboration with IIT Kanpur is working to develop a fibre optic-based load monitoring system for civil aircrafts. Towards this, Hansa-3 aircraft available at the Flight Laboratory of IIT Kanpur is proposed to be used as the platform for demonstration of this technology. The wing spar was identified as crucial structural component to be monitored using such system. In order to develop load estimation algorithms for the aircraft wing, a study was conducted on a ground test article identical to the main spar of the Hansa-3 wing. The focus of the present work was to apply known loads / load distributions to the ground test article and measure strains at critical locations of the spar using Fibre Bragg grating (FBG) sensors. The ground test article was tested for all the critical load cases under four-point bending condition. Strains measured during tests and known bending moments (obtained from wing design report) were used to develop mathematical models (algorithms) which can then be used to estimate bending moments. The models estimated bending moments with very good accuracy with average error in estimation being 5% and maximum error being 14%. The outcome of this study will directly assist in development of algorithms or mathematical models for load estimation in the aircraft wing.