Downloaded from https://www.everyspec.com ADS-79D-HDBK Finite Element Model Crack Length Crack Tip Stress Loading Profile Load Crack Growth Equation Stress table n K U C dN da ) ( Crack Length K min K max 1.5 30.29 27.92 2 27.25 25.68 2.5 21.52 21.23 3 19.47 17.82 Cycle Shapes Crack Progression Estimate Crack Length as obtained from Physics Based Model - FIGURE D-10. An example of a framework for model based development of CIs no different for CBM systems than for any Test and Evaluation (T&E) results of other major systems on the aircraft. Section D.7 is a good example of an approach to the CI creation process for the Apache aft hanger bearings. D.7 IN-SERVICE APPROACH EXAMPLE:
CI CREATION PROCESS FOR APACHE AFT HANGER BEARINGS. A relatively simple process was followed to develop a condition indicator (CI) for the aft hanger bearings on AH-64 Apache helicopters. The resulting CI has proved to be effective in the detection of both naturally-occurring faults in the field and seeded faults on test stands. The CI development process is described here to serve as a guide for bearing CI development on other components and on other platforms. D.7.1 Design Goals and Evaluation Criteria. The goal of CI development is to design one or more algorithms that produce scalar values that each strongly depend on some aspect of a component‘s condition.
A CI‘s effectiveness is based on the strength of this dependence and is judged on the basis of its contribution to the ability of a health indicator (HI) to provide accurate recommendations concerning maintenance. The performance of a CI can only be evaluated in the context of its contribution to an HI. The Modern Signal Processing Unit (MSPU) HI algorithm applies thresholds to each CI value so that each one is categorized with a status color. The HI algorithm then takes the highest status color of the most recent values for the CIs associated with a particular fault group and provides a maintenance recommendation based on this maximum fault group status.
Every CI does not need to respond to every 92