The T700 SECAD Project – Damage Tolerant Control Design for Turboshaft Engines

Digital propulsion controls provide the foundation for adding capabilities beyond normal control functions to provide the capability to detect and accommodate damages to a turboshaft engine in near real-time and to provide control reconfiguration capability for continued safe operation of the damaged engine. The early detection of not only the onset of damage (and thus the specific engine which sustained damage in typical twin engine applications) but the identification of damage type as well, provides critical pre-cursors for the control system to react to prevent further system damage. The engine selected for this study is the T700-701E with FADEC (Full Authority Digital Electronic) Controls. The methodology is based on an extension of linear regression to not only detect that damage has occurred (and for which engine in a twin-engine configuration), but the identification of the type of damage as well. Additionally, the SECAD (Survivable Engine Control Algorithm Development) methodology also 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”. T700 SECAD project considers compressor, combustor, and turbine damage modes with the goal of maximizing the torque producing capability of the engine without generating false alarms. Preliminary results from simulations as well as the analysis of test results from actual ballistic testing at China Lake are encouraging.