In an effort to promote the use of Ada in embedded system development, a realistic avionics application model whose hard real-time properties are fully predictable has been generated. This was done starting with a rate monotonic analysis of a set of typical fully synchronized periodic and aperiodic avionics tasks drawn from an idealized attack aircraft mission computer. The authors describe this avionics case study and its goals, examine the resulting design issues and trade-offs, and investigate the ability of the rate monotonic analysis model to predict its performance under a heavy load.>