Fuel System

Question 1

How many fuel tanks are there?

Answer 1

Two in each wing, a main tank and collector tank for a total of four tanks for the aircraft.

Question 2

What is the capacity of the fuel tanks?

Answer 2

406.8 gallons total with 402 gallons usable.

Question 3

How is the fuel tank vented?

Answer 3

Through inward and outward vents located on the bottom of the wing.

Question 4

How is pressure kept equal in both tanks?

Answer 4

A cross vent line.

Question 5

How can fuel gravity feed between the tanks?

Answer 5

A flapper type check valve allows gravity feed between the tanks but does not allow backflow.

Question 6

Where are the drains?

Answer 6

A single fuel drain is located at the lowest point in each tank.

Question 7

How do the jet pumps work?

Delivery Ejector and Transfer Ejector

Answer 7

They use motive flow supplied from the low pressure engine driven fuel pump.

Question 8

How does a jet pump work?

Answer 8

Flow enters the jet pump, its flow is increased as it passes through a venturi which creates low pressure drawing fuel in from the tank through a suction inlet.

Question 9

What does the transfer jet pump do?

Answer 9

Transfers fuel from the main tank to the collector tank.

Question 10

What does the delivery jet pump do?

Answer 10

Transfers fuel from the collector tank to the common fuel line.

Question 11

Describe the electrical fuel pump?

Use?

Answer 11

28 VDC electrical pump located in the bottom of each collector tank.
Provides fuel pressure during engine start and in the event of a low pressure engine driven pump failure.

Question 12

How is the Electrical Fuel Pump controlled?

Answer 12

A single switch on the overhead panel, either in ON or AUTO.

Question 13

When does the electrical pump come on if in AUTO?

Answer 13

If the low pressure switch on the air separator senses fuel pressure below 2 PSI, CAWS FUEL PRESS will illuminate.
The boost pumps will remain on for 10 seconds after the pressure rises above 3.5 PSI.

Question 14

What illuminates when the boost pumps are in operation?

Answer 14

CAWS L/R FUEL PUMP

Question 15

What illuminates when the air separator senses fuel pressure below 2 PSI?

Answer 15

CAWS FUEL PRESS (boost pumps will cycle on)

Question 16

How does the automatic fuel balancing system work?

Answer 16

When the EIS senses a difference exceeding 5% between tanks it activates the boost pump in the tank with more fuel, stopping flow from the tank with less fuel.
There is a 1 minute delay in pump activation to avoid excessive operation in turbulence.

Question 17

What refueling imbalance error can the Automatic Fuel Balancing system handle?

Answer 17

up to 40 gallons/4 LCD segments on the ground.

Question 18

If the auto balancing system fails how can you manually restore balance.

Answer 18

Placing the boost pump for the side with greater fuel in the ON position.

Question 19

Describe fuel flow under normal operation from the Wing Tank through the Firewall Shutoff.

Answer 19

1. Wing Tank
2. Transfer Ejector Pump
3. Collector Tank
4. Delivery Ejector Pump
5. Common Manifold
6. Maintenance Shutoff
7. Fuel Filter (or bypass)
8. Air Separator, Fuel LP switch
9. Firewall Shutoff

Question 20

Describe fuel flow under normal conditions from Firewall Shutoff to Fuel Nozzles.

Answer 20

1. Firewall/Cockpit shutoff.
2. LP Engine Driven Pump (or internal bypass)
3. Fuel/Oil Heat Exchanger
4. HP Engine Driven Pump
5. Filter (or bypass)
6. FCU
7. Fuel Flow Transducer
8. Fuel Flow Divider and Dump Valve.
9. 14 duplex type Fuel Nozzles.

Question 21

What does the air separator do with removed air?

Answer 21

Passes back to the tanks through the Vent Return Line.

Question 22

Where is the low fuel pressure switch?

Answer 22

Incorporated in the air separator.

Question 23

Where is the Low Pressure Engine Driven Fuel Pump and how is it operated?

Answer 23

The LP engine driven fuel pump is mounted on the AGB and is driven by the external oil scavenger pump.

Question 24

Can fuel still get past the LP Engine Driven Fuel Pump if it fails or is not on yet?

Answer 24

Yes, it has an integral bypass that allows fuel under electric boost pump pressure to bypass during start or when the pump fails.

Question 25

What are the temperatures for flows in the oil to fuel heat exchanger?

Answer 25

Max oil flow when fuel is below 21 C.

No oil flow when fuel is above 32 C.

Question 26

What drives the High Pressure Engine Driven Pump?

Answer 26

It is driven by the AGB.

Question 27

What does the FCU do?

Answer 27

Regulates the amount of fuel going to the engine in response to PCL, CL, or MOL.

A 3D cam takes PCL/Condition Lever inputs and transfers to fuel valve.

Question 28

What does the Fuel Flow Transducer do?

Answer 28

It converts the fuel flow rate into an electrical signal which is displayed on the EIS in PPH.

Question 29

What does the Fuel Flow Divider and Dump Valve do?

Answer 29

Splits metered fuel between primary and secondary manifolds as a function of fuel pressure.

Dump valve is connected to the purge system and an accumulator charged with P3 air. Blows residual fuel into the combustion chamber on shutdown.

Question 30

How is fuel quantity measured?

Answer 30

5 sensors per wing for a total of 10.

• 4 sensors in each main tank.
• 1 sensor in each collector tank.

Question 31

CAWS FUEL LOW illuminates when?

Answer 31

Fuel quantity drops below 20 gallons in the associated wing.

Question 32

What is the max fuel to land with in the 45/47?

Answer 32

45-1200 lbs.

47-1400 lbs.

Question 33

How much fuel do we burn per hour average?

Answer 33

400 lbs.