Lifing methods and safety criteria in aero gas turbines

Modern gas turbines engines concentrate high power into a relatively small machine, e.g. more than 50 MW in each engine suspended from the aircraft wing in a large civil transport application. The rotational speed of the shafts reaches as high as 13,000 rpm in large engines and even higher in smaller engines as used in helicopters. Hence there is both a concentration of thermal energy in the combustion process and kinetic energy in the rotating parts that presents issues for structural integrity. This paper describes the regulatory requirements that must be achieved to allow operation of engines in civil applications and at how these requirements are satisfied in practice. It concentrates on those parts whose failure can directly threaten the integrity of the airframe through the generation of hazardous effects. The main issues are associated with fatigue through cyclic operation of the engine and the ability of the engine to survive abnormal conditions in such a way that the aircraft can safely land and be brought to rest.