Expert SHM and CM of Turbojet Engine FCU Using Instantaneous Angular Speed Signal

Abstract

The control quality and technical condition of the engine control system (fuel control unit, FCU) plays a key role in the safe operation of aircraft. The article presents a comprehensive approach to diagnosing FCU in transient states. At the beginning, examples of damage to aircraft engines caused by FCU’s incorrect work were presented, and the difference in perception of FCU by the designer and diagnostician was indicated. A transfer of the status observer was proposed for a reliable diagnosis of the FCU technical condition (reverse problem). Instead of registering and analysing several parameters (including pressure and fuel flow, exhaust temperature, pressure, etc.) and temperatures at the inlet to the combustion chamber) in steady states, the registration of the instantaneous angular speed (IAS) in the transient states of the engine and the analysis of its parameters on the phase plane is proposed. Next, the methodology of active experiments was discussed, in which the functions of FCU components and new diagnostic symptoms were identified. The methodology for creating expert software has been approximated. Finally, the experience of the long-term operation of the method in Poland has been presented. The very high efficiency of the diagnostic method in identifying hidden FCU failures and regulation errors has been demonstrated, which is also influenced by human factors. The topics discussed will be illustrated by examples.