Why is turbine engine control complex?
Because of extreme forces, temperatures, and pressures, and the need to avoid stall, surge, overspeed, overtemperature, or flameout.
What is the primary method of turbine engine control?
Control of fuel flow to the engine.
What parameters are continuously monitored for engine control?
Speeds, temperatures, pressures, and valve positions.
How is the engine normally controlled after start?
By the thrust lever with minimal crew intervention.
What additional functions can the fuel system perform besides metering fuel?
Hydraulically actuating components such as bleed valves and variable stator vanes.
What is the purpose of the low-pressure fuel pump?
To ensure adequate fuel flow to the engine.
Why does fuel pass through oil coolers?
To cool engine/IDG oil and warm the fuel.
What is the purpose of the high-pressure fuel pump?
To raise fuel pressure for proper atomisation in the combustion chamber.
Why is excess fuel returned via a bypass line?
The pump always supplies more fuel than required.
What are the three main types of engine control systems?
Hydro-mechanical, electronic supervisory control, and FADEC.
What characterises hydro-mechanical fuel control systems?
Mechanical and hydraulic components with no electronics.
What was a limitation of hydro-mechanical control systems?
They could not automatically compensate for changing atmospheric conditions.
What is electronic supervisory control?
A computer that fine-tunes engine rpm during steady-state operation.
When is electronic supervisory control inactive?
During transient engine conditions.
What does FADEC stand for?
Full Authority Digital Engine Control.
What is the main advantage of FADEC?
Improved safety, efficiency, and engine life.
What component commands fuel flow and actuators in a FADEC system?
The Electronic Control Unit (ECU).
How many channels does a FADEC ECU have?
Two independent channels (A and B).
What is hot standby in a FADEC system?
One channel controls the engine while the other monitors and is ready to take over.
What triggers a FADEC channel swap?
An output failure in the active channel.
What is the Cross Channel Data Link (CCDL)?
A communication link between FADEC channels.
How is engine-specific configuration provided to FADEC?
By data or programming plugs attached to the engine.
What is FADEC normal mode?
Full performance with constant thrust for a given thrust lever position.
What is FADEC alternate (soft reversion) mode?
Engine holds its current condition due to loss of key inputs.
