The Engineering Analysis SYstem (EASY) computer program is summarized in this report. It provides techniques for analysis of steady-state and dynamic (transient) environmental control system (ECS) performance@ control system stability@ and for synthesis of optimal ECS. General uses of a transient analysis computer program for ECS design and development@ and general features of EASY relative to these uses@ are presented. This report summarizes the nine analysis options of EASY@ EASY program organization for analyzing ECS@ data input to the program and resulting data output@ and a discussion of EASY limitations. Appendices provide general definitions for dynamic analysis@ and samples of input and output for EASY. Purpose: A generalized computer program for determining transient thermodynamic performance of aircraft ECS@ and methods for dynamic analysis of aircraft ECS are discussed in this report.