Enhancing Damage Tolerance Analysis with Method-Specific Probability of Detection Data

Damage tolerance analysis provides the analytical basis for structural fatigue assessment and inspection planning in transport category aircraft and is required for certification under contemporary airworthiness regulations. In current practice, damage tolerance analysis commonly relies on generalized assumptions for initial flaw size and prescriptive inspection intervals without explicitly incorporating differences in nondestructive inspection detection capability.

A baseline damage tolerance analysis was conducted on a simplified structural configuration selected to illustrate the underlying concepts without unnecessary analytical complexity, using established industry and regulatory assumptions. The analysis was repeated with the initial crack length defined by inspection capability. The results demonstrate that the assumed initial flaw size governs inspection initiation and is directly related to the maximum probable undetected flaw required by certification regulations, resulting in substantial shifts in inspection timing.

A cumulative probability of detection formulation is introduced to evaluate inspection strategies in terms of total detection reliability, enabling alternative combinations of inspection method and frequency to achieve equivalent detection performance. This approach provides flexibility in inspection method selection and interval definition and may enable the use of lower-cost or more readily deployable inspection techniques while maintaining the required level of structural reliability. The proposed framework establishes a direct linkage between crack growth prediction and inspection capability, improving analytical consistency while preserving regulatory intent.