In this study, combustion efficiency of a military type turboprop engine is determined at various loads with the aid of emission data. Also, emission data collected from the engine run at various loads by experimental methods is used to introduce emission parameters such as the emission index, the power emission index and the energy emission index. The calculation method of the power emission index and the energy emission index for a turboprop engine is incorporated in literature by this study. Additionally, the relationship between determined parameters is proven in this study. As a result of the study, the combustion efficiency of the engine is found to be variable between 97.8% and 99.9%, as expected from a modern aircraft engine. (C) 2014 Energy Institute. Published by Elsevier Ltd. All rights reserved.