Aircraft fuel system

The most optimum engine operation can be realized by supervisory engine management since it enables the pilot to select the most appropriate thrust setting quickly and accurately. Irrespective of the changes in atmospheric conditions, the engine thrust can be maintained at a level predetermined and set by the pilot who can change again the thrust settings to his requirement by changing the thrust lever angle, in which case, the engine adjusts to the new thrust setting without overshooting of N2 or temperature. Thrust is not controlled directly by supervisory control unit, which calculates the value of the main control parameter (N1 or EPR) corresponding to the demand thrust to obtain N1 command or EPR command. This function is called ‘power management’ and the calculating unit is called ‘power management control’ (PMC) (Diesinger 89). Supervisory engine management is used in proven hydro-mechanical fuel control to obtain complete control over all engine functions and is characterized by a mechanical backup which monitors engine control in case of failure of the electronic control. Supervisory engine management systems, thus, perform functions necessary for engine operation and protection enabling reduction of crew work load and maintenance costs and constitute the last designs using hydro-mechanical control systems (Diesinger 89).
The FADEC engine management system uses an electronic control system with a digital computer as the only control unit. The FADEC engine management has taken over all steady state and transient control intelligence replacing most of the hydro-mechanical and pneumatic elements of the supervisory engine control system (Maclsaac and Langton 70). The capability of the digital computer to process a large number of parameters is fully utilized by the FADEC system. The FADEC engine management system provides engine system regulation and scheduling for thrust control in addition to