Power(engine) control system is one of the major aircraft systems containing complex avionics systems. Strict requirements are put to the power control system to ensure reliability. In addition, control system must ensure the efficiency of operational modes and contribute to high performance parameters. Avionics systems of the power unit should provide maximum automation. Their main task is to minimize pilot attention to the engine. Pilot must control engines only during startup, or when something happens, or when some system parameters do not correspond to the normal values.
Engine control systems shall monitor and control all parameters of the engine using numerous sensors. In the case when some parameters are out permissible values, alarm system shall notify the pilot and try to normalize the values of these parameters using a specially built-in algorithms.
Generally structure of the power unit control system depends on the number of engines, their location, type and level of automation. Nowadays turboprop and turbojet engines are used on civil aircraft.
Engine starting up is important flight preparation procedure. During startup pilot should control all engine parameters and check that they have reached a desired mode and will ensure the stability and reliability of operation.
Start up and power unit monitoring procedure is highly dependent on the type and manufacturer. Therefore, different automation algorithms are used and thus different avionics equipment unique for each type of engine are applied. Start up is the most complicated procedure. The final decision on the serviceability of the engine takes pilot-in-command because some criteria for analyzing the functioning of automatic algorithms are difficult.
During the flight equipment used for monitoring should be thoroughly analyze all parameters of the engine and systems in real time to ensure its work. Special attention is given to control of acceleration, speed, change of parameters that exceed permissible limits, and modes of operation.
The typical structure of turbojet engine is shown in Fig. 179. It consists of areas of low and high pressure.
Fig. 179. Structure of the turbojet engine
Full Authority Digital Engine Control (FADEC) is used on modern aircraft to manage and control the parameters of the power unit. Effective control through FADEC can increase resource performance and fly at the lowest fuel cost. The general structure of FADEC construction shown on Fig. 180. It consists of the systems of:
- control of temperature regimes in different parts of the engine
- control of the change in air pressure
- management and control of lubrication
- fuel supply control
- monitoring of compressors
- start up
- engine reverse
- changing the frequency of rotation
- control of the temperature of gases
- control of vibrations of rotors
Fig. 180. General structure of FADEC construction
Start up equipment shall ensure:
- startup on the ground
- startup in the air
- cold startup
- false startup
- automatic startup completion
FADEC control and monitoring of parameters of the power unit is provided by the ECAM, which is a part of the EFIS. Fig. 181. Displaying the parameters of the power unit on ECAM
ECAM displays following basic information for the pilot:
- quantity of fuel
- quantity of oil
- temperature and oil pressure in the engine
- temperature of gondola
- magnitude of vibrations
- state of oil and fuel filters
- alarm of any deviations from the normal parameters
- alarm of operating modes