A method and an on-board system for detecting impact on an impeller wheel of an aircraft engine. Deflection signals representative of the deflections on the blades of the impeller wheel are acquired. Each of the deflection signals is correlated with a pulse signal typical of an impact on a sound blade at the rotation frequency of the engine, in order to identify impacts on the impeller wheel. The impact signals are extracted from among the deflection signals. The impact signals are transmitted to the ground in order that the signals are analyzed to detect defects on the blades of the impeller wheel.