5-8 Fuel Systems SQ
The tendency of a fuel to vaporize refers to its __________
The minimum temperature at which a combustible liquid emits a sufficient quantity of vapor that ignition will occur during a momentary application of a flame.
What type of fuel is used during shipboard operations? Why?
JP-5, less volatile, higher flashpoint.
An increase in temperature will cause what change, if any, in volatility? In flashpoint?
Increase the volatility.
Flashpoint always remains constant.
What are the major considerations in designing a fuel system?
1. Operation at low atmospheric pressures.
2. Complexity of the piping system.
3. Cold weather starting.
4. High fuel flow pressure.
What controls the amount of fuel delivered to the combustion chamber?
How does the pilot communicate with the Fuel Control Unit (FCU)?
Through the PCL
List the various operational parameters the FCU must process to deliver the proper fuel flow to the engine.
1. PCL inputs.
2. Compressor inlet temperature.
3. Compressor rpm (highpressure RPM in dual spool).
4. Turbine inlet temperature.
Describe the emergency/manual fuel system.
Pilot controls amount of fuel supplied to the burner and the rate of application. Pilot must monitor the engine's critical limits.
Why is a boost pump included in the aircraft fuel system?
To avoid vapor lock or engine fuel pump cavitation.
What part does the FCU play during engine starts?
Sends pressure signal to close the dump valve at engine start.
What is the position of the pressurizing and dump valve during an engine start? During normal engine operation? During engine shutdown?
Both valves closed; dump valves closed and pressurizing valve open; dump valve open and pressurizing valve closed.
What cuts off fuel flow during engine shutdown?
Where does metered fuel begin in the aircraft fuel system?
After the FCU
What is military rated thrust?
The maximum thrust for a specified limited period of time (30 minutes).
What component measures the proper amount of fuel flow to the afterburner?
Afterburner fuel control unit
5-8 Fuel Systems SQ