200 Fuel System

Question 1

What provides static and dynamic venting for the fuel tanks?

Answer 1

NACA vent scoops under the Wings provide static and dynamic venting.

Question 2

Where are the collector tanks located?

Answer 2

The two collector tanks are located in the center tank at a point that is lower than the left or right wing thanks.

Question 3

Explain the construction of the wing fuel tanks

Answer 3

The wing tanks are a wet wing design. A sealant is used to seal the tanks so this makes the wing the tank

Question 4

How is gravity De-fueling accomplished

Answer 4

A gravity defueler adapter can be inserted into the fuel drain valves to accomplish gravity de fueling

Question 5

How is fuel prevented from flowing to the wingtip during wing low maneuvers?

Answer 5

There are one way flow valves in each wing tank that prevent the flow of fuel to the wing tip.

Question 6

Explain the fuel vent system.

Answer 6

The NACA scoops have vent Lines connected to the tanks to provide static and dynamic pressure. In flight the NACA events will provide ram air pressure to maintain a positive pressure on the fuel in the tanks. Static ventilation of the tanks during ground operations is provided through the NACA vents.

Question 7

During climb you notice the total fuel in the center tank increase by 300 pounds, is this a problem?

Answer 7

This is not a problem. Is possible for fuel to flow to the center tank from the vent system during climb and cause fuel quantity readings of the center tank to increase as high as 300 pounds.

Question 8

What monitors and controls the operation of the fuel system?

Answer 8

A dual channel fuel system computer

Question 9

Do both fuel computer channels operate at the same time?

Answer 9

One channel operates at a time. When the active channel fails, the standby channel will assume control.

Question 10

Where is the temperature of the fuel measured?

Answer 10

Left-wing tank
and
In the fuel line to each engine

Question 11

Explain the general operation of ejector pumps.

Answer 11

Motive fuel flow asked come from a source like the engine high-pressure fuel pump. This motive flow is passed through a venturi-shaped nozzle. The fuel exits the nozzle at an increased velocity that creates a low pressure. This low pressure creates a suction that draws fuel out of the tank.

Question 12

What powers the fuel ejectors?

Answer 12

Motive flow from the engine high pressure pump. High pressure fuel flows through a venturi-shaped nozzle of the ejector, which creates a low pressure. This then draws fuel out of the tank by suction.

Question 13

How is fuel transferred from the wing tanks to the collector tanks?

Answer 13

Fuel is transferred by scavenge ejectors. A scavenge ejector is located at the lowest inboard point of each wing tank.

Question 14

How is fuel moved from the collector tank to the high-pressure engine driven fuel pump?

Answer 14

There is one main ejector pump for each collector tank. Motive flow to operate the main ejector is provided by the high pressure output of the engine driven fuel pump.

Question 15

How are the boost pumps powered?

Answer 15

The boost pumps are DC powered.

Question 16

What are the purposes of the electric fuel boost pumps?

Answer 16

To transfer fuel from the collector tanks to the engines.
As a back up to the main ejectors when the ejector fails.
Provide fuel pressure during engine start.

Question 17

Are the electric booster pumps required for engine start?

Answer 17

No, the engines will start without them.

Question 18

When will the electric boost pumps operate with L and R boost pump switch light selected?

Answer 18

Both pumps will operate when the fuel computer detects low fuel feed pressure in either feed manifold

Question 19

Which electric boost pump will operate with Just DC power?

Answer 19

The left DC pump

Question 20

Explain the transfer ejectors?

Answer 20

There are two transfer ejectors located in the aft section of the center tank and perform the job of transferring fuel from the center tank to the wing takes. Moto flow created by the high-pressure output of the main ejectors operates the transfer ejectors.

Question 21

Explain the engine fuel shut off valves (SOV).

Answer 21

The associated ENGINE FIRE PUSH switch light on the glareshield electrically controls the SOV. Their purpose is to stop the flow of fuel to the engines. This switch light is located on the emergency bus so it is always powered.

Question 22

Where is the engine fuel temperature indication located?

Answer 22

On the FUEL synoptic page.

Question 23

How is the fuel heated before it enters the engine?

Answer 23

The fuel is heated by a fuel/oil heat exchanger located on each engine. Hot engine oil passes through the heat exchanger to heat the fuel.

Question 24

How many fuel filters are installed?

Answer 24

There is one fuel filter PER engine

Question 25

What would happen if the fuel filter becomes contaminated?

Answer 25

An impending bypass switch monitors the filter for contamination. If a low fuel pressure is sensed, an EICAS message will alert the crew. The filter will then be bypassed to continue to provide fuel to the engine.

Question 26

Explain the XFLOW/APU pump?

Answer 26

This DC Powered pump is used to supply fuel to the APU from both wing tanks equally and perform crossflow operations. The pump is located in the aft portion of the center wing box in the main landing gear bay.

Question 27

Explain the APU fuel shut off valve (SOV).

Answer 27

The APU SOV is used to stop the flow of fuel to the APU. This SOV is opened and closed by the APU FIRE PUSH switch light or by the PWR FUEL switch light on the APU Control Panel

Question 28

Explain the APU negative gravity relief valve

Answer 28

This is a spring-loaded valve, which allows pressurized fuel from the right engine fuel feed manifold to feed the APU during two conditions. The valve would open if the XFLOW/ APU fuel pump fails. OR A negative gravity condition that exists in flight.

This valve is not indicated on the fuel synoptic page

Question 29

What are two methods to crossflow fuel?

Answer 29

Powered crossflow [automatic or manual]

Gravity crossflow

Question 30

Explain the operation of the automatic power crossflow.

Answer 30

Automatic crossflow operation is initiated when there is a fuel in balancing more than 200 pounds between the wing tanks. The crossflow/APU pump is powered and fuel is taken from both wing tanks. The crossflow valve on the low quantity side will open to fill the low side to 50 pounds above the other side. This operation is enabled with the system is not in manual mode.

Question 31

Explain the manual powered crossflow operation.

Answer 31

This feature is used with the automatic power crossflow does not respond to an imbalance. The pilot can select the XFLOW AUTO OVERRIDE switch light to MANUAL, which will inhibit the automatic power crossflow system.

The L or R cross flow SOV switch light can be selected on a low tank side. Selecting this switch light will cause the XFLOW/APU pump to activate and the crossflow valve to open on the side selected. The pilot must turn off the crossflow by deselecting the L or R XFLOW AUTO OVERRIDE switch light once balance is achieved. This will cause the valve to close and the XFLOW/ APU pump to turn off.

Question 32

When will the FUEL IMBALANCE caution message appear on the EICAS?

Answer 32

When there is an in balance of 800 pounds between the wing tanks.

Question 33

What does the amber fail light in the GRAVITY/XFLOW switch light indicate?

Answer 33

The gravity XFLOW SOV is not in the commanding position.

Question 34

What should the pilots do to transfer fuel from the center tank to the wing tanks?

Answer 34

This process is completely automatic. As long as the engines are running.

Question 35

When will the fuel total turn Amber?

Answer 35

900 pounds

Question 36

When will the bulk fuel temperature in the left wing turn Amber?

Answer 36

-40° C and below.

Question 37

When will the left or right fuel feed temperatures turn Amber?

Answer 37

5°C or less