Non-destructive testing:the guarantee of the success of full scale aircraft fatigue test

The full scale aircraft fatigue test(FSAFT)is crucial for determining the fatigue life (or service life based on flight hours) of an aircraft group and for understanding its performance during whole service life. So far, FSAFT is the only means in correctly obtaining the fatigue life of an aircraft group. The early locating and finding repairable cracks and damages in critical structures of the aircraft during fatigue test is the key factor for the successful fulfillment of the test and for the correct determination of fatigue life of corresponding aircraft group. The comprehensive application of effective non-destructive testing (NDT) means, together with acoustic emission real time monitoring during the process of the entire test was shown to be the guaranteeing factor for the success of the FSAFT. The technical details of NDT of aircraft critical structures during full scale fatigue test were introduced. Descriptions were specially given to the acoustic emission (AE) monitoring and early damage prediction. Case studies included the monitoring of the central wing, and the central wing/outer panel jointing areas. New approaches to the AE data processing were employed because of the requirement for the real time and in-time monitoring of the structures throughout the fatigue test. Due to the extremely long time period spanned by the test, say 3-4 years, data acquisition and processing was faced with very high challenges. By using the combination of trend analysis of statistic AE parameters, time-based and amplitude-based filtering, and spatial filtering techniques, together with multi-parameter identifications, real time and in-time monitoring of the critical structures was realized, proving the effectiveness of current methods. The integration of NDT means with AE monitoring played key roles for the fulfillment of the FSAFT.