Fuel

Question 1

What is the quantity of each main tank?

Answer 1

2500kg

Question 2

What is the purpose of the ventral surge tanks?

Answer 2

Ensures positive surge pressure and allows up to 2% thermal expansion without spillage. They are 100 L each and are vented back into the main tanks.

Question 3

What is the purpose of the wing center box?

Answer 3

There is no fuel stored here and it is just provided for the transit of fuel cross feed pipes. To prevent vapor concentration the box is drained and vented.
Engine Feed

Question 4

What is the purpose of the feeder tanks?

Answer 4

Always full to protect the engine feed system against negative and lateral factors.

Question 5

How many pumps? Capacity Lt and KG, of the feeder tanks?

Answer 5

2 Pumps, 200 Lt and 160 KG.

Question 6

What is the purpose of the HMU (hydro mechanical unit)?

Answer 6

Provides fuel pressure to the engine and associated jet pump in the fuel system. The jet pump is located in the feeder compartment.

Question 7

What is the function of the motive flow valve?

Answer 7

The jet pump is activated by HP fuel from the engine HMU and is controlled by a motive flow valve. It is closed during cross feed to the associated engine, ie cross feed R to L, left valve closed.

Question 8

When does the electro pump run?

Answer 8

In normal operations it will only run during engine start then the jet pump takes over. The electro pump is de engerised 30 sec after the pressure is greater than 8.5 PSI.

Question 9

What pressure in the jet pump will cause the electro pump to start?

Answer 9

5 PSI.

Question 10

What is the logic of the fuel cross-feed?

Answer 10

A cross-feed valve, controlled by an electrically operated actuator, allows both engines to be fed from one side or one engine to be fed by either tank, allowing control of an unbalance situation.

Question 11

Max imbalance?

Answer 11

730 KG or 1609 LBS. 200 KG LND

Question 12

Look at the cross feed procedure 2 ENG, 1 ENG?

Answer 12

When the cross-feed valve is open, a blue “FUEL X FEED” light comes on memo panel. In this case, the two electrical pumps are automatically actuated. It’s possible to use only one fuel tank by switching off the opposite pump PB.

Question 13

Can the fuel LP valve be controlled by the crew?

Answer 13

Through the associated fire handle.

Question 14

What does the pump PB do?

Answer 14

PUMP PB pressed in, will allow the pump to automatically run if, delivery low pressure to the jet pump is detected. The motive flow valve will open but remain closed until sufficient pressure is provided 30 seconds after HP fuel pressure is available and normal jetpump functioning is sensed by the 600 mbar (8.5 PSI) pressure switch, electrical pump is
automatically switched off.

Question 15

What does the FEED LOW PRESS light indicate?

Answer 15

FEED LO PR illuminates with the CCAS when up stream of the LP valve is less than 4 PSI, this indicates starvation or pump failure.

Question 16

Where are the different fuel temperature measuring devices located?

Answer 16

1 is located in the left feeder compartment. 1 located before each of the HP pumps.

Question 17

What does the FUEL CLOG light indicate?

Answer 17

Indicates a HP pump fuel filter pressure greater than 45 psi

Question 18

What is the definition of fuel low quantity?

Answer 18

When the quantity is 160 KG, but the feeder tank is not full (feeder jet pump failure).

Question 19

What does a fuel test PB perform?

Answer 19

TEST PB will check both measurement channels and, if the functioning is normal, display all 8’s. At the same time, CCAS is activated, MC flashes amber, SC is heard.

Question 20

What does a LOW LEVEL light indicate?

Answer 20

LO LVL illuminates amber and the CCAS is activated when quantity of the concerned display becomes lower than 160 kg ; in addition, the corresponding electrical pump is automatically actuated.

Question 21

What are the limitations with fuel indication?

Answer 21

On the ground, attitude within -3 deg and +1 deg of pitch and +/- 2 deg of roll is: +/- 1% of full scale near zero or +/- 3% of full scale near full. All other ground flight conditions outside this envelope (pitch, roll) accuracy will be degraded.

Question 22

What type of fuel sensors does the fuel measurement system have?

Answer 22

Six probes in each fuel tank measure the relationship of the dielectric constant and its density to obtain a signal proportional to the mass of the fuel.

Question 23

What are the refuel defuel pressures?

Answer 23

50 and 11 psi.

Question 24

What are the two different high level detection methods?

Answer 24

Normal operations, FQI (fuel quantity indication) is responsible for the high level detection, the associated valves are then shut.

In the case of a FQI failure, high level detection is achieved by a level sensor in the bottom of each surge tank, when activated the high level is illuminated on the refuel panel.