The Validity of Schmidt-Appleman Criterion for Modern Turbofan Engines: A Numerical Study

Many excellent books on aviation are available for a beginner student. However, for those who wish to get a first introduction to the field, a study of multiple sources of extensive scope is needed. Furthermore, available texts require a background of fluid mechanics and often also compressible flow and turbomachinery. For this introductory text, only basic knowledge of mechanics is required, and the text then develops all the necessary concepts. The material presented herein brings knowledge together on the modelling of aircraft and the analysis of aero engines. It also touches upon aircraft and engine certification, emissions predictions and discusses how aviation affects climate. Several small but conscious steps have been taken to keep complexity to a minimum, for instance avoiding multiple definitions of thrust and efficiency and providing examples that are interconnected. The analysis of the cruise performance of a modern aero engine is included in the appendix together with a sample prediction on NOx emissions and the use of the Schmidt-Appleman criteria to evaluate conditions for contrails formation. We predict aircraft performance using an aircraft model that matches the engine, hence the analysis is based on a state-of-the-art existing aircraft-engine-pair currently in commercial operation.