The service life of an engine is determined by evaluating finite element structures in order to investigate temperature and stress parameters for a specified time period. In his research on life cycle of an engine.Broede argues that rotational speeds and engine intake are functions of time and assume a typical real flight mission with respect to the life consumption of the engine components. Broede further indicates that damage calculation show structure locations that have highest life consumption and forms foundation for declaring critical areas of structures that should be monitored. The stress in these areas is determined by the monitoring system and the temperatures are determined from structural points that forms a good approximate of thermal stresses at the specified critical areas. This is done by monitoring algorithms and should satisfy modeling of the heat conduction. Pfoertner proposes determination of gas path temperatures computation of heat sources as this is a derivative of metal temperature development of the structure. This facilitates modeling that is based on approximated performance designs. The power function model is represented as T gas *=a+ b (N rot *) c where T gas * and N rot * are thermodynamically reduced gas temperature and rotational speed 1 and variables a, b and c are individual gas temperatures from calculation of design performance. If the temperature points of a compressor inlet and outlet temperatures T gas 1 represent T gas 2 are available and the temperature points consisting of several stages with a long extension in axial direction are considered, the linear combination of them will be T gas = (1-c) . T gas ; 1+c . T gas 2. This combination is used with different values of c which represent the corresponding points of the gas temperatures. Harrison indicates that development of metal temperatures requires a discreet dynamical system that is derived from Fourier’s heat conduction operation by discretisation subject to the time and spatial coordinates. The temperatures in each point are calculated stepwise starting with an initial temperature distribution. The temperature at time step i follow from its value at the previous time step i -1. A leading temperature T lead is assigned which depends on the selected gas temperature T gas : T lead (t) =T lead (i-1) +a . (b . T gas (i) -T lead (i-1). The leading temperature T lead and temperatures of at least three neighboring points T j determines the increment of metal temperature of the considered point T (i) =T (i-1) +c.(T lead (i) -T (i-1) +∑dj(Tj (i-1) -T (i-1) . This implies that the change in metal temperature is directly proportional to the difference between gas heat transfer and the conductivity of the metal. The variables a, c, dj are functions of rotational speed N rot and are power functions of the form e+ f . (N rot /N rot . ref ) g with a given reference speed N rot.ref and constants e, f and g. A combination of speed, pressure and gas temperature can be used instead of dependency on the rotational speed N rot. The variable b depends on rotational speed and is calculated normally for about five selected speed valves conditionally to meet the steady state of metal temperatures for these speeds, the b values for other speeds are linearly interpolative. The more or less