Optimizing Inspection Intervals Through Risk Evaluation in Aircraft Structures

Abstract As aircraft fleets age, maintaining operational readiness at an affordable cost becomes increasingly challenging. This is largely due to the rise in Preventive Maintenance Task Requirements (PMTRs) outlined in the Aircraft Maintenance Program (AMP). While aging aircraft may require more frequent inspections, leveraging data from prior inspections enables the optimization of inspection intervals based on risk, ensuring cost efficiency by minimizing unnecessary downtime, while maintaining the required safety level. The primary objective of the AMP is to ensure the airworthiness and operational readiness of an aircraft system throughout their service life. To achieve this, it is essential to establish an acceptable level of risk as a basis for determining optimal PMTR recurrence. The SMART|DT tool, developed with FAA funding, provides a robust framework for conducting risk assessments of aircraft structures using Probabilistic Damage Tolerance Analysis (PDTA), which effectively assesses and manages the risk of structural failure. During the sustainment phase of the Swiss Air Force F/A 18 fleet, data-driven analyses within SMART|DT, and other tailored statistical tools, were performed to evaluate the risks associated with various PMTR intervals. This paper will explain the methodology applied to both Safe-Life and Damage-Tolerance structures, with real-world applications to demonstrate how inspection intervals can be optimized. By doing so, PMTR recurrence can be fine-tuned to enhance aircraft readiness and program affordability while maintaining an acceptable level of safety.