In compliance with certification requirements, engine manufacturers must demonstrate the safe and reliable engine performance within a predefined flight envelope, including high altitude operation. Generally, high altitude testing of aero engines requires large amount of energy. With the aerospace supply chain continuously reducing its environmental impact, the requirements on the eco-efficiency on altitude testing increase as well. Consequently, the operation of Altitude Test Facilities (ATF) is subject to on-going improvements. Thermodynamic models that describe the generation of the altitude conditions are an important foundation for improvements of the altitude test procedures. One-dimensional network models are well suited to generate such models, since they are modular, standardized, and easy to configure. Yet, their calibration over the required wide range of configurations and operating conditions is a challenge. This results in a model which matches different operating points of the facility with varying precision. Modeling approaches which involve measured data promise an improvement in this respect and offer potentially real-time optimization of the facility operation. It is shown that the application of such models allows a transparent derivation of operating standards for altitude testing. The associated reduction of the environmental impact of altitude testing is significant.
