Investigation of the autogyro main rotor blade failure after flight tests

• Hybrid UAV tested under simulated failure of interacting rotor and propeller systems. • Profilometer and CT scan revealed surface and internal rotor blade damage. • ARAMIS system tracked deformation under tensile load in damaged blade. • Propeller impact damage found non-critical for further blade operation. • Study validates combined NDT and DT methods for rotor blade failure analysis. The structural integrity of main rotor blades is critical for the safety and reliability of rotorcraft and hybrid unmanned aerial vehicles (UAVs). Redundant propulsion systems enhance flight reliability by enabling continued operation or safe landing following a partial failure. The XGyro aircraft exemplifies such a system, combining multirotor propulsion with autorotation from a gyroplane. This study investigates the effect of localized impact damage on the tensile strength of a carbon fiber composite rotor blade from a hybrid UAV after a controlled in-flight collision with a rear propeller. The damaged blade was compared with an undamaged reference blade of identical design and material composition. Non-destructive evaluation revealed surface cracking, delamination, and internal spar damage, while destructive tensile testing showed that the damaged blade maintained a maximum load capacity 36% higher than that of the undamaged reference. Strain mapping confirmed that the highest stress concentrations occurred in the blade attachment zone rather than in the impact area, and no further damage propagation was observed during testing. These results demonstrate that certain localized impact damages may not critically reduce the residual tensile capacity of rotor blades, provided that attachment integrity is preserved. The findings contribute to damage tolerance assessment methodologies for composite rotor blades and provide experimental data for the validation of computational models of impact-damaged aerospace structures.