<div class="section abstract"><div class="htmlview paragraph">An important part of future air vehicle design will be the development of a transient integrated aircraft system model. DC electric power system modeling poses particular challenges because they are highly dynamic and employ short time constant line replaceable units [<span class="xref">1</span>, <span class="xref">2</span>, <span class="xref">3</span>]. This paper describes an approach to modeling an aircraft's electric power system that uses simplified non-physics based models of the line replaceable units that are part of future 270V_DC aircraft power systems. The model is an alternative to physics based models and is particularly useful for the initial phases of aircraft development before hardware development has occurred. A 270V_DC aircraft power system model is constructed as an example using the unit models. Selected results will be presented.</div></div>