Failure Indication and Corrective Action for Turboshaft Engines

In order to prevent loss of power modulation capabilitv in the event of a failed engine control sensor, an automatic in-flight Failure Indication and Corrective Action (FICA) strategy is developed for advanced turboshaft helicopter applications. FICA, as designed, provides for both the detection of a failed sensor and the generation of the best estimate of the failed signal which can then be used to provide continuity of stable engine control. The technical basis of FICA is a constant gain extended Kalman filter. The FICA structure consists of a nonlinear model of the turboshaft engine along with update logic to force the model to track the actual engine behavior. The details of the engine model and update logic are discussed in functional form. Utilizing the results of extensive computer simulations with an advanced turboshaft engine, the T700-GE-700, it is shown that stable engine control can be maintained in the presence of multiple sensor failures. Additionally, FICA is shown to have significant impact on Diagnostics and Condition Monitoring by making available engine parameters which are not normally measured. The structure of FICA is suitable for implementation in an engine-mounted full authority digital electronic control.