The aim of the project is to develop an account of explanation in engineering science. In contrast to explanation in the physical sciences, life sciences, and social sciences, very little philosophical work has been done on this subject. Our specific aims are (i) to describe and elucidate the explanatory practice of engineering scientists, (ii) to develop an account of the value and adequacy of different types of explanations in explanation-seeking contexts in engineering science, and (iii) to develop an account of how the explanatory practice of engineers relates to the realization of the ultimate aim of (improved) design, and to assess the goodness of the ways in which explanatory formats are used to meet this aim. In order to reach these aims we will investigate cases from mechanical and electromechanical engineering. General insights from the philosophical literature on scientific explanation and explanatory power, as well as insights from the philosophy of biology, are used to select appropriate cases and as tools to analyze these cases. The project enriches the philosophy of explanation by incorporating engineering science, and is innovative from a philosophy of technology perspective because of its focus on explanation.