The SECAD project - vulnerability reduction via propulsion control logic

Digital propulsion controls provide the foundation for adding capabilities beyond normal control functions to enable the next level of increased survivability for both war-time and peace-time damage scenarios. Propulsion is a critical system for any platform, providing electrical and hydraulic power, ECS (environmental control system) air as well as thrust. If the vulnerability of propulsion systems can be reduced, the probability of successful completion of the mission is increased. The SECAD (survivable engine control algorithm development) project has made significant progress toward the development of a complete system to not only diagnose, but also to react to non-catastrophic damage to the engine gas path in real-time and thus preserve thrust needed to enable mission completion, intelligent mission re-planning, or just getting the pilot "out of harms way". The early detection of not only the onset of damage but also the identification of damage type as well, provides critical precursors for the control system to react to prevent further system damage. Initial feasibility results, which were presented at IEEE Aerospace Conference in 2002 [Frankenberger, C and Pisano, A (2002)], have been significantly extended and validated to suggest potential for early transition. These new results demonstrate the simplicity of the concept by extending the design to cover the entire flight envelope of interest and are shown to be robust to normal deterioration and typical aircraft transients. Although based on an extension of linear regression, the methodology determines the optimum sensor suite from a given set of sensors with varying accuracies to achieve a desired probability of correct detection in the presence of normal system variations while minimizing the probabilities of unacceptable "false alarms". The SECAD project recently completed a highly successful demonstration of this "full-envelope" damage detection and mitigation design using an F414-GE-400 turbofan engine at the Naval Air Warfare Center Weapons Division's Weapons Survivability Laboratory. Testing consisted of fan and compressor damage, combustor damage, afterburner duct damage and ballistic nozzle damage. Test results verified the capability of the damage detection and mitigation methodology over the frill range of throttle positions at selected conditions.