Fuel Control Systems

Question 1

What is the function of the fuel control unit/

Answer 1

An engine-driven accessory that meters the appropriate amount of fuel in response to thrust lever setting.
Operates Hydromechanically

Electronic engine controller

FADEC

Question 2

Other than the FMU what features does a turbine engine have to limit the engine from exceeding set parameters?

Answer 2

Pressure control
Flow control
Pressure ratio control
acceleration control
all these being achieved through the use of a governor.

Question 3

What is the function of the electronic engine controller (EEC)

Answer 3

The EEC is reading the parameters of the engine and responds to the pilot’s power requirements and applying the appropriate fuel flow to achieve that power for the given engine and atmosphere parameters.

Question 4

What is the ideal mixture ratio of air/fuel?

Answer 4

15:1 (Air:fuel)

Question 5

What are some of the fuel identification methods for an aircraft?

Answer 5

Type of fuel the a/c uses
Flight manual info
Label near the filler cap
Tech log

Question 6

What is the colour of jet fuel?

Answer 6

Colourless or straw

Question 7

What is the identification of Jet A fuel?

Answer 7

Question 8

What is the Identification of Jet A-1 Fuel?

Answer 8

Question 9

What is the identification of Jet B fuel?

Answer 9

Question 10

How is the FCU effected in changes of specific gravity?

Answer 10

The FCU feeds more or less fuel as required to changes in specific gravity.

Question 11

What is the purpose of the main fuel pump and where is it located?

Answer 11

It supplies fuel to the FMU and is housed within the FCU. It supplies more than enough fuel and the metering valve will control the flow to the burners.

Question 12

What is the purpose of the fuel heater?

Answer 12

To prevent any freezing of water content in the fuel that could go on and block the filters. Helps with atomization.

Question 13

Explain the function of the Fuel filters?

Answer 13

Usually, two fitted one before the pump and one after the fuel pump to remove contamination of the fuel that may cause blockage or wear to components.

Question 14

What are some speed limiting devices in the fuel system?

Answer 14

Mechanical flyweight systems

Electronic RPM sensors connected to the ECU

Question 15

What are the different types of fuel Nozzles?

Answer 15

Simplex Type

Duplex Type

Vaporizer Tubes (Hockey Sticks)

Question 16

What is the purpose of fuel nozzles?

Answer 16

Atomising or vaporising the fuel to ensure rapid burning

Question 17

Explain the Simplex type

Answer 17

Consists of one chamber which induces a swirl into the flow, it is used on smaller turbines or as a start nozzles as it is restricted by limited fuel flow.

Question 18

Exlpain the duplex Nozzle?

Answer 18

Consists of two spin chambers, a primary and secondary(main)

The primary chamber handles lower flows and the secondary chamber valve will open when fuel pressure increases and provides larger fuel flow to the engine.

Question 19

Explain the Vaborizer tubes/hockey sticks?

Answer 19

Do not require full atomization, fuel is injected into the vaporizer tube and it is vaporized as it travels through the tube before being released at the front of the combustion chamber.

Question 20

Explain the operation of the dump valve?

Answer 20

During engine shutdown, a spring-loaded dump valve opens to drain the fuel, to prevent vaporizing within the system leading to blockages.