The Effect of Rated Climb Performance on Low Cycle Fatigue of a Civil Turbojet Engine

Abstract

Low cycle fatigue (LCF) of jet engine disks is a major contributor to the maintenance costs of an engine. The current industry standard for the analysis of LCF is to use representative flight missions to reflect the in-service usage of engines. Based on the engine performance during those missions, the internal stresses and temperatures of life-critical components are calculated. These stresses and temperatures define the cyclic life consumption of a mission and determine the certifiable LCF life of the engine. The engine performance is defined by the power setting schedules of the engine, so-called engine ratings. The effect of the rated climb performance on high pressure turbine (HPT) disk life is investigated for a generic two-shaft engine operated in a small twin-jet civil aircraft. LCF life is analyzed using a finite element (FE)-based cycle counting model. The aircraft climb performance resulting from the changed climb ratings is assessed with an aircraft performance model. It is shown that there are climb ratings which result in reduced LCF life consumption and climb time compared to the reference rating. Employing these ratings on in-service engines increases the certifiable life count and reduces maintenance costs.