Downloaded from https://www.everyspec.com ADS-79D-HDBK The remediation process provides the means to trade repair tolerance for retirement time. Utilization of actual usage and loads provides the means to extend the retirement time at acceptable levels of risk. The steps in the remediation process follows: a. Categorize and quantify the primary reasons for component removal and decision not to return the component to service (based upon available field data). b. Investigate regime recognition data for causal relations between usage and damage. c. Perform engineering analysis on the component and evaluate the impact of expanded repair limits on static and fatigue capability.
Regime recognition data provides information on load severity and usage for projecting revised fatigue life. d. Perform elemental or full-scale testing to substantiate analysis. e. Implement the results of the analysis and testing phase by adjusting repair limits and repair procedures where applicable, thereby increasing the useful life of the component and reducing part removals. The result is an increase in damage repair limits in the Technical Manuals (TMs) and Depot Maintenance Work Requests (DMWRs) allowing the component to stay on the aircraft longer.
Remediation enhances the four goals of FLM and can be considered a subset of analysis and correlation of data to component fatigue strength. A.5.4 Managing service life of damage tolerant structure. FLM will provide necessary usage and loads data for continual airworthiness support of damage tolerant aircraft structure. The categories of damage tolerant structure include: slow crack growth structure, fail-safe multiple load path structure, and fail-safe crack arresting structure. 5 A potential application is in the establishment of inspection requirements for airframe hot spots where fatigue cracking is discovered during the service life of the aircraft.
When coupled with appropriate flight load survey data, the FLM derived actual usage, a direct load measurement or an updated usage spectrum will provide the load spectrum data to establish the inspection procedure and frequency required to achieve the reliability requirement of section A.6 to prevent a catastrophic failure. The inspection would be performed until a repair or appropriate design change of the critical structure is incorporated in the fleet. The FLM collected data would also be used in the substantiation of the repair/redesign. The damage tolerance repair or new design should be substantiated to meet the goal of two design service lives without fatigue cracking.
6 The inspection requirements for the repair/redesign must be substantiated to the reliability requirements of section A.6 to prevent a catastrophic failure. The FLM database will be utilized in the evaluation of existing structure, repairs, reinforcements, and redesigns. Also, the FLM system has the potential to provide input to the user that fatigue damage is occurring during sustained flight conditions (example level flight). The avoidance of or minimum duration in such a condition will significantly reduce aircraft fatigue damage and subsequent repair or catastrophic loss.
Application of FLM has the potential of significant improvements in readiness and reduction of sustainment costs for Army aircraft systems. 5 JSSG-2006, Department of Defense Joint Service Specification Guide, Aircraft Structure, 30 October 1998. 6 JSSG-2001B, Department of Defense Joint Service Specification Guide, Air Vehicle, 29 Jan 2009. 38