“Considerations for U. S. Army Turbine Engine Component Life Analysis”

Past operational experience with military helicopter engines has generated recognition within industry and the military of a critical need for a more complete definition of the assumptions and conditions used to determine safe life limits for helicopter turboshaft engine components. Since both developmental and derivative engine designs continue to expand previously established design experience, the definition of realistic assumptions, coupled with the removal of unnecessary conservatism, has become necessary for the establishment of safe life limits and for maintaining the safety of fielded engines after qualification. This paper addresses the following considerations utilized by engine manufacturers and approved by military qualifying agencies when establishing safe lives for Army engine components. • High sensitivity of component life to assumed operating conditions (altitude, ambient temperature, Mach number, and level of engine deterioration). • Selection of appropriate design conditions for different engine components with different modes of failure (high cycle fatigue, low cycle fatigue, creep, stress rupture, and oxidation). • Methods (statistical analysis, Monte Carlo technique, etc.) used to combine distributions of design variables (material property, pattern factor, part geometry, control tolerances, applied loads, etc.) that influence safe life. • Assumptions and techniques for damage summation with complex and variable missions • Validation of life calculations with testing (engine, spin pit, etc.) and condition monitoring (inspections). • Need for accurate systems (hardware, software, operational models, and life usage algorithms) to continuously monitor engine component life usage