Downloaded from https://www.everyspec.com ADS-79D-HDBK Structural reliability is based on the number of inspections and the probability of detection of each inspection. It is noted that slow crack growth damage tolerant structure is difficult to achieve in a rotorcraft load environment. As such, prognostics for US Army rotorcraft structure are not considered to include continued flight with known damage beyond any substantiated flaw tolerance for the component. One method of improving structural prognostics would involve developing and introducing improved integrated-NDI (or traditional NDI) capabilities.
Typically, NDI capabilities may be improved by introducing new methods, techniques, and equipment which reduce the size of detectable damage (for example the crack length with 90% probability of detection with 95% confidence). A second method of improving structural prognostics would involve incorporation of individual component fatigue damage assessment into fleet management. By trending accumulated fatigue damage and seeking methods to correlate fatigue damage to controllable aspects of aircraft usage, commanders would be able to more efficiently and proactively manage aviation assets.
Component replacement could be scheduled prior to component life expenditure based on the observable trends. Reduction in usage scatter would improve the prediction capability and increase the horizon to scheduled replacement. A separate V&V Process for structural prognostics is not required. Although not an airworthiness concern, it is recommended that the general V&V Process described in Figure K-5 be followed for any formalized infrastructure investments in accumulated fatigue damage trending and fleet management tools which incorporate use of individual fatigue damage assessment data to predict fatigue life expenditure. K.6.
GROUND STATION VERIFICATION AND VALIDATION PROCESSES One of the goals and desired benefits of HUMS is to be a transparent collector of information during normal operational missions. As such, the methods used to determine component health and aircraft usage statistics, and the approaches designed within the system in the form of algorithms and processing, should be shown to be proven and effective for collecting and analyzing such data. A very high correlation between the data collected and the HUMS- determined health of a specific component should be demonstrated to validate the data collection method and to verify the proper operation of the system.
The Ground Station is designed to be the database and software tool where operational data and usage statistics are stored and analyzed to determine component health. This section also outlines the methodologies used to verify and validate Ground Station (GS) systems to support overall HUMS functionality on Army aircraft. References to RTCA DO-178B will be used throughout this section to outline verification processes in relation to ground station approval. Verification guidance and specific procedures developed for verification should remain consistent with the potential impact to the system of erroneous operation or hidden fault modes.
Systems monitoring components that have a high degree of criticality to the safe and continued operation of the mission or aircraft should be subjected to a higher degree of verification than 219