Fuel System Flashcards by C G

Which part of the fuel tank contains the negative G compartment?

The Collector tank.

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What fuel pumps does the cockpit Fuel Pump Switch control power to?

The engine booster pumps and the jet pump booster pump.

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Can the LP Cock close with the fuel pump switch set to on?

No - to close LP cock, at least one LP Cock switch must be set to Closed and at least one Fuel Pump switch must be set to OFF.

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What is the maximum refuelling pressure?

50PSI/ 3.45 Bar.

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Where is the main fuel vent located?

To the LHS of the parachute box.

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Describe the flow of fuel from the centreline tank to the engine.

Centreline Tank -> Fuselage Bag Tank -> Wing Tank -> Collector Tank.

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Assuming an SG of 0.79, what is the capacity (in kg) of each fuel tank.

Centreline Tank: 358kg
Fuselage Bag Tank: 638kg
Wing Tank: 639kg

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What is the total fuel capacity of the Hawk with a CLT attached?

1635kg.

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Name the four types of fuel pumps used in the Hawk T2.

DC Starter Pump
Engine Booster Pump
Jet Pump Booster Pump
Jet Pumps.

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State the purpose of the DC starter pump.

To provide fuel to the engine and APU during an engine start before Aux Gen online.

To provide fuel during an airborne relight if both generators offline.

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What busbar supplies power to the DC Starter Pump?

The 28V DC ESB

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State the purpose of the Engine Booster Pump.

Supplies fuel to the engine and APU (via the main heat exchanger) when AC power is available.

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Where does the Engine Booster Pump draw fuel from?

The top or bottom of the Negative G Compartment.

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What happens if the Engine Booster Pump fails?

A bypass spill valve allows the engine to draw fuel from the bottom of the Negative G Compartment.

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Which busbar supplies the Engine Booster Pump with electrical power?

The 200V AC Main Busbar.

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What is the purpose of the Jet Pump Booster Pump?

To create the fuel flow required for the Motive Flow used in the Jet Pumps.

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Where does the Jet Pump Booster pump draw fuel from?

The bottom of the Negative G Compartment. Note: does not draw any fuel whilst under negative G.

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Which busbar supplies the Jet Pump Booster Pump with electrical power?

The 200V AC Main busbar.

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What is the purpose of the Jet Pumps?

To transfer fuel from the outer wing tanks to the collector tank.

They also act as airlock generators in the case that one wing tank empties before the other, preventing the collector tank level dropping before the outer wing tanks are empty.

What pressure is the HP air used to pressurise the fuel system pressurised to?

4PSI above the datum air pressure (datum source provided by ram air).

What will cause the TRANS caption to illuminate?

When the fuel transfer pressure is below normal.

What happens if the CL Transfer switch is set to Override?

The CL tank is isolated, and fuel drawn from internal tanks instead.

At what fuel level does the FUEL caption activate?

What should you assume?

When the negative g compartment contains less than 160+-25kg.

Assume you only have 135kg of fuel left.

Why is there a 10 second time delay built into the FUEL caption?

To prevent spurious alerts due to fuel sloshing around.

What does it mean if the total fuel and CL contents indications on the EMP flash? What triggers this? What is required for the display to return to normal?

Centreline Tank Transfer Failure. CL contents greater than 25kg and internal tank total less than 1090kg. CL contents falls to less than 25kg and internal tank total rises above 1255kg.

Why does the FUEL bold face get you to deselect the combat flap?

With combat flap extended, the FUEL caption is locked in, even if the conditions leading to it have reverted to normal. Once CF deselected, the caption may go out if everything is okay.

Is pressurisation required to transfer fuel from: The CL tank to the fuselage tank? The fuselage tank to the wing tanks? The wing tanks to the collector tank?

Yes. No. No.

What switch controls fuel supply to the engine and APU?

The LP Fuel cock.

Fuel pressure to the engine is supplied by the engine booster pump. What happens when this fails? What consideration accompanies this?

A bypass valve allows fuel to be drawn from the bottom of the negative-g compartment. Fuel will no longer be pumped from the top of the negative g compartment when inverted. i.e. don't go inverted.

You look at the EMP and notice that the CL tank readout has disappeared. What does this mean? What do you need to do? Why?

CL contents has reached zero. Podge the button until you can see the CL tank contents again, despite the fact it is reading zero. There is a danger that fuel might start re-feeding into the CL tank, but you would not know if the display has disappeared.

What does it mean when the FUEL caption illuminates? What should you assume?

The float indicates that there is less than 160+-25kg of fuel left in the negative g compartment. Assume that there is only 135kg (160-25) remaining.

What do the jet pumps in the collector tank do?

Transfer fuel from the outer wing tanks to the collector tank.

Where does the jet pump booster pump draw its fuel from?

The collector tank.

What happens to the jet pump booster pump under negative g?

The pump intake is not immersed. Therefore, fuel flow from the outer wing tanks to the collector tank stops.

What do the main and auxiliary heat exchangers cool? What do they use to do the cooling?

They cool the oil from the engine driven main generator system. Fuel is used to cool the oil.

Where are the main and auxiliary heat exchangers located? Where do they draw the fuel from to do the cooling?

Main heat exchanger located in the negative g compartment and uses fuel supplied by the engine booster pump. The aux heat exchanger is located in the collector tank and uses fuel supplied by the jet pump booster pump.

How is fuel supplied to the APU and engine during an engine start?

By the DC starter pump.

What does it mean if "CL" is displayed on the EMP but no fuel value? What should you assume? What will the TOTAL contents be showing?

The CL contents signal is invalid. Assume fuel not available. Total fuel will not include any CL contents.

When may the total fuel contents pause in its reduction? Why?

At about 645kg. This is about the changeover point between fuselage and wing tanks and the fuel probes do not fully cover the gap.

What is likely to have happened if the CL tank fuel contents on the EMP shows zero but does not disappear? What do you need to do?

There is a control problem. The transfer valves in the wing may not have opened, and the internal fuel system may not have pressurised. Carry out the centreline tank transfer failure drill.

What does the TRANS caption mean?

There is a fuel system pressure control valve issue - there is insufficient fuel transfer pressure to allow fuel to transfer from the external tanks.

When will the "Bingo" audio alert go off? What happens on the EMP when this occurs?

Once the total fuel remaining goes below the bingo fuel level set on the EMP for more than 30 seconds. The Total fuel display will flash for 15 seconds.

What may cause a FPR caption?

An engine booster pump failure or a blockage through the engine supply filter.

How much of a time delay is placed on the FUEL caption once fuel falls below the set level? Why is it there?

10 seconds. To prevent spurious warnings.

Under what circumstances will the FUEL caption remain on, even if fuel levels rise above the set level that activates the caption?

When landing gear and/ or flaps are down. | When Combat Flap is selected.