High Cycle Fatigue: A Mechanics of Materials Perspective part 63. The nomenclature used in this book may differ somewhat from what is considered standard or common usage. In such instances, this has been noted in a footnote. Additionally, units of measurement are not standard in many cases. While technical publications typically adhere to SI units these days, much of the work published by the engine manufacturers in the United States is presented using English units (pounds, inches, for example), because these are the units used as standard practice in that industry. The graphs and calculations came in those units and no attempt was made to convert. | 606 Appendix H capable of operating to the next subsequent depot interval to avoid immediate teardown when damage is detected and determined to be within acceptable limits. REQUIREMENT LESSONS LEARNED Blades insufficiently designed for FOD considerations have caused In-Flight Shut Downs IFSDs and costly damage to the engine. FOD tolerance can be enhanced by use of more damage tolerant materials and a redistribution of the blade mass. Foreign object damage costs the Navy over 15M each fiscal year based on a conservative estimate in one source reference. Common culprits are housekeeping items such as nuts bolts safety wire screwdrivers etc. This paragraph is aimed at this type of FOD problem environmental factors such as ice sand water and birds are covered in other specification paragraphs . Foreign object damage FOD . The requirements of shall be verified by VERIFICATION RATIONALE Analysis demonstration and test are required to ensure that the fan and compressor airfoils can meet the operational requirement of and to establish accept or reject criteria for damage that is detected during flight line inspections. VERIFICATION GUIDANCE Past verification methods have included analysis demonstration and test. The following verification procedure may be used for guidance. Simulated foreign object damage shall be applied to the a critical stage blades at one or more sections of the b of the airfoil. The damage applied shall produce at least the stress concentration factor Kt of . Following the foreign object damage application the damaged blades shall be tested to the life required in . At the completion of the test there shall be no evidence of blade failure or flaw sizes beyond values allowed by the in-service inspection flaw size of as the result of the foreign object damage. Sufficient instrumentation for monitoring the structure of the engine shall be included in the test engine. Appendix
