Recent developments in the area of digital propulsion controls have precipitated requirements for compact real-time dynamic engine simulations. This paper describes the analytical development and experimental validation of a full range, non-linear model of the F404-GE-400 afterburning turbofan engine. Unique approaches were used to obtain a highly compact model which is capable of being operated in an engine mounted airborne digital computer. The model served as a signal source in a failure protection scheme, providing an unusual basis for model validation. Highlights of the very successful broad ranging validation and use of this model* are provided.