Downloaded from https://www.everyspec.com ADS-79D-HDBK (Copies of these documents are available online at http://www.astm.org or from the ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959.) B.2.2.2 Other Government documents, drawings, and publications. The following other Government documents, drawings, and publications form a part of this appendix to the extent specified herein. (Copies of this document are available from http://www.tc.faa.gov/its/worldpac/techrpt/ar04-3.pdf ) or write Office of Aviation Research, Washington, D.C. 20591. B.3 DEFINITIONS Structural Usage Monitoring:
Managing fatigue lives via Usage Monitoring B.4 GENERAL GUIDANCE In a standard scheduled maintenance program, component retirement times (CRTs) are derived from the total expected exposure to regimes for which flight strain survey data is available. This expected exposure is based on a design mission spectrum determined by the class of aircraft. In a CBM system, however, component life calculations can be refined through knowledge of the actual service amount of operational time spent in each flight regime. CRTs can be extended when an aircraft is actually exposed to less severe mission profiles.
Alternatively, in the interest of safety, CRTs can be reduced in the presence of more severe mission profiles than accounted for in the original CRT calculations. The process begins with identifying the set of flight regimes encountered in the mission spectrum for the class of aircraft. For each regime, the strains/loads are determined during the flight load survey performed during the development phase of the aircraft. Next, analysis is performed to determine the rate of life expenditure due to fatigue as a function of time or number of occurrences under the regime load for each component for which airworthiness credits are sought by the CBM system.
Finally, one should develop an onboard instrumentation package that measures the flight state of the aircraft to enable accurate classification of the flight regime. An accurate characterization of the operational flight regime is a key characteristic of the CBM system. A dynamic maintenance measurement system should not be implemented that might compromise flight safety in an attempt to extend operational life. Therefore, the flight regime classification system should be submitted to a rigorous validation procedure that guarantees component 42 ASTM INTERNATIONAL (AMERICAN SOCIETY FOR TESTING AND MATERIALS) ASTM E1049-85(2011)e1 Standard Practices for Cycle Counting in Fatigue Analysis.
ASTM D664-11A Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration. DEPARTMENT OF TRANSPORTATION DOT/FAA/AR-04/19 Hazard Assessment for Usage Credits on Helicopters Using Health and Usage Monitoring System