Abstract GasTurb 11 and the Gas Turbine Simulation Program (GSP) 11 are two commercially available gas turbine simulation programs used by industrial professionals and academic researchers throughout the world. The two programs use a pseudo-perfect gas assumption in their calculations, where the specific heat is taken as a function of temperature and gas composition but not pressure. This assumption allows the two programs to make more realistic calculations of gas turbine engine performance. Australian Standard As 5601 Gas Installations South there. This is in contrast to the ideal and perfect gas assumptions used in classroom calculations. In addition, GasTurb 11 and GSP 11 both utilize component maps, comprised from test data, to model off-design turbojet component behavior. This is different from the referencing technique where off-design performance is calculated based on the ratio of off-design to on-design conditions. This thesis presents a comparative study of the two simulation programs with the traditional ideal-perfect gas calculations and the referencing technique.