Output Feedback Control of Jet Engine Stall and Surge Using Pressure   Measurements
  The problem of controlling surge and stall in jet engine compressors is of fundamental importance in preventing damage and lengthening the life of these components. In this paper, we use the Moore-Greitzer mathematical model to develop an output feedback controller for these two instabilities (only one of the three states is measurable). This problem is particularly challenging since the system is not completely observable and, hence, none of the output feedback control techniques found in the literature can be applied to recover the performance of a full state feedback controller. However, we show how to successfully solve it by using a novel output feedback approach for the stabilization of general stabilizable and incompletely observable systems. 
Manfredi Maggiore and Kevin Passino