FUEL SYSTEM 737-300 400

737-300/400 FUEL SYSTEM

Kelompok :

FARIZ E K

M ZIA A

RASYID A M XII AP I

737-300/400 Fuel SchematicThere are three fuel tanks: No. 1, Center, and No. 2. The No. 1 and No. 2 fuel tanks are located in the interspar area of each wing. The center fuel tank is contained in the fuselage (wing center section).

A pressure fueling station is installed on the right wing leading edge. A fueling receptacle allows a hose to be connected for fueling. Shutoff valves control fuel distribution to the tanks.

One surge tank can be found outboard of each wing fuel tank. Vent channels allow the surge tanks to collect any fuel overflow from the main tanks. A surge tank drain line then allows the fuel overflow to drain back into the center tank, but prevents fuel flow from the center tank to the surge tank. Each surge tank has a capacity of approximately 30 U.S. gallons.

A fuel vent scoop is located on each outboard lower wing surface, under the surge tank. The scoops create positive pressure during flight and are the overboard vents for the vent system. If a significant amount of overflow fuel is collected in a surge tank, the fuel will be discharged overboard via the vent scoops. The scoops are designed to prevent ice accumulation.

The No. 1 fuel tank contains a forward and aft fuel boost pump. Each pump is AC powered and is fuel cooled and lubricated. The forward pump is attached to the forward wing spar and the aft pump is installed in a dry bay within the fuel tank. The wing spar and dry bay isolate the pump motor from the fuel in the tank.

Fuel from the tank enters each pump through a wire mesh screen via a suction tube inlet. Fuel is discharged from the pump under pressure through the boost pump check valve. The check valves

To APU

APU fuelshutoffvalve

APU bypassvalve

Bypassvalve

No. 1fuel tank

No. 1engine

No. 2engineEngine driven

fuel pump

Bypassvalve

Center fuel tank No. 2fuel tank

Engine fuelshutoff valve

Engine drivenfuel pump

Engine fuelshutoff valve

Manual defueling valve

Center left

pump

Center right pump

No. 2 fwd

pump

No. 2 aft

pump

Center right pump inletCenter

left pump inlet

No. 1 fwd

pump

No. 1 aft

pump

Fueling receptacle

When pulled,closes No. 1 engine

fuel shutoff valve

When pulled,closes No. 2 engine

fuel shutoff valve

Fuel temperatureindicator

Pressure fuelingstation

Surge tankSurge tank

Crossfeed valve

Scavengevalve Scavenge

inlet

Center tank

scavenge jetpump

Fuel shutoffvalves (3)

are located inside the fuel tank and will open when respective fuel pump pressure is approximately 12 psi.

The No. 1 tank fuel LOW PRESSURE lights will illuminate when the respective fuel pump switch is ON and fuel boost pump pressure is low. The LOW PRESSURE lights will also illuminate when the respective fuel pump switch is OFF.

Prior to fuel entering the No. 1 engine, it must first pass through the engine fuel shutoff valve. The valve is electrically (DC) opened when the No. 1 engine start lever is positioned from CUTOFF to IDLE. The valve closes when the start lever is lowered from IDLE to CUTOFF. The valve also closes when the No. 1 engine fire switch is pulled.

From the engine fuel shutoff valve, fuel is delivered to the No. 1 engine via the main engine control (MEC).

A bypass valve allows fuel to be drawn out of the tank by an engine driven fuel pump. This would only occur if both No. 1 fuel tank pumps were to fail. The engine driven fuel pump is attached to the engine gearbox.

A fuel temperature sensor is located in the No. 1 fuel tank. The fuel temperature indicator displays the results in °C.

The No. 2 fuel tank contains a forward and aft fuel boost pump. Each pump is AC powered and is fuel cooled and lubricated. The forward pump is attached to the forward wing spar and the aft pump is installed in a dry bay within the fuel tank. The wing spar and dry bay isolate the pump motor from the fuel in the tank.

Fuel from the tank enters each pump through a wire mesh screen via a suction tube inlet. Fuel is discharged from the pump under pressure through the boost pump check valve. The check valves are located inside the fuel tank and will open when respective fuel pump pressure is approximately 12 psi.

The No. 2 tank fuel LOW PRESSURE lights will illuminate when the respective fuel pump switch is ON and fuel boost pump pressure is low. The LOW PRESSURE lights will also illuminate when the respective fuel pump switch is OFF.

Prior to fuel entering the No. 2 engine, it must first pass through the engine fuel shutoff valve. The valve is electrically (DC) opened when the No. 2 engine start lever is positioned from CUTOFF to IDLE. The valve closes when the start lever is lowered from IDLE to CUTOFF. The valve also closes when the No. 2 engine fire switch is pulled.

From the engine fuel shutoff valve, fuel is delivered to the No. 2 engine via the main engine control (MEC).

A bypass valve allows fuel to be drawn out of the tank by an engine driven fuel pump. This would only occur if both No. 2 fuel tank pumps were to fail. The engine driven fuel pump is attached to the engine gearbox.

The DC powered crossfeed valve connects the left and right fuel manifold. It provides a means of directing fuel to either engine from any tank.

The center fuel tank utilizes the left and right fuel boost pump. Each pump is AC powered and is fuel cooled and lubricated. The center left pump is installed in a dry bay within the No. 1 fuel tank. The center right pump is installed in a dry bay within the No. 2 fuel tank. The dry bay isolates the pump motor from the fuel in the tank.

Fuel from the center tank enters each pump through a wire mesh screen via a suction tube inlet. Fuel is discharged from the pump under pressure through the boost pump check valve. The check valves are located inside the fuel tank and will open when respective fuel pump pressure is approximately 1.3 psi.

As previously stated, the main tank and center tank check valves open at a boost pump pressure of approximately 12 and 1.3 psi, respectively. Therefore, assuming fuel in all three tanks and all six pumps operating, fuel is delivered to the engines from the center tank first due to the lower “cracking” pressure of the check valves.

The center tank fuel LOW PRESSURE lights will illuminate when the respective fuel pump switch is ON and fuel boost pump pressure is low. The LOW PRESSURE lights will extinguish when the respective fuel pump switch is OFF.

A center tank fuel scavenge system is installed to drain unusable fuel from the center tank into the No. 1 tank. This occurs when both center tank pump switches are positioned to OFF. This action sends an electrical signal to the scavenge valve to open for a time period of 20 minutes.

With the scavenge valve now open, fuel from the No. 1 fwd pump flows to the center tank scavenge jet pump. This results in low pressure being created in the scavenge inlet. Remaining fuel in the center tank is now drawn out and drained into the No. 1 tank. The scavenge valve will close at the end of 20 minutes. The scavenge valve may be re-opened, for 20 minutes, by cycling the center pump switches to ON and back OFF.

Fuel may be delivered to the APU from any one of the three tanks. The APU fuel shutoff valve controls delivery of fuel to the APU. The valve is opened and closed by the APU start switch. Pulling the APU fire switch will also close the APU fuel shutoff valve.

With no AC power available to the aircraft, all six fuel pumps are inoperative. If attempting to start the APU with no AC power on the aircraft, the fuel pumps are not available to feed fuel to the APU. Therefore, an APU bypass valve is located in the No. 1 fuel tank which allows fuel to be drawn out of the tank for APU operation. The APU cannot draw fuel out of the No. 2 or center tank.

The manual defueling valve is located inboard of the pressure fueling station on the right wing front spar. It controls fuel flow from the fuel manifold to the pressure fueling station. It is used to defuel any one of the three tanks, or to transfer fuel from tank to tank (on the ground only). The handle of the defueling valve is such that its access door cannot be closed when the defueling valve is in the open position.

Although not shown in the schematic above, overwing fill ports (for gravity fueling) are provided for the No. 1 and No. 2 fuel tanks. These receptacles would be utilized if pressure fueling facilities are not available. If fuel is desired in the center tank during this type of scenario, fuel must be transferred from the main tanks via the manual defueling valve.

Fuel Control Panel

FUEL VALVE CLOSED lights:

Illuminated bright blue –

• Related engine fuel shutoff valve in transit.

• Related engine fuel shutoff valve position disagrees with start lever or engine fire warning switch position.

Illuminated dim blue –

• Related engine fuel shutoff valve is closed.

Extinguished –

• Related engine fuel shutoff valve is open.

FUEL TEMP Indicator:

Indicates fuel temperature in the No. 1 fuel tank only.

FILTER BYPASS Lights:

Illuminated –

Impending fuel filter bypass on respective engine due to a contaminated filter.

Note: During a FILTER BYPASS, fuel is routed around the filter and delivered to the engine unfiltered.

CROSSFEED Selector:

Controls fuel crossfeed valve.

Open –

Connects left and right fuel manifold.

Closed –

Isolates left and right fuel manifold.

Crossfeed VALVE OPEN light:

Illuminated bright blue –

• Crossfeed valve in transit.

• Crossfeed valve and CROSSFEED selector disagree.

Illuminated dim blue –

• Crossfeed valve is open.

Extinguished –

• Crossfeed valve is closed.

CTR Tank Fuel Pump Switches (L and R):

ON –

Activates respective center tank fuel pump.

OFF –

Deactivates respective center tank fuel pump.

Center Tank Fuel Pump LOW PRESSURE Lights:

Illuminated –

Respective fuel pump switch is ON and output pressure is low.

Extinguished –

• Respective fuel pump switch is ON and output pressure is normal.

• Respective fuel pump switch is OFF.

Main Tank Fuel Pump Switches (FWD and AFT):

ON –

Activates respective main tank fuel pump.

OFF –

Deactivates respective main tank fuel pump.

Main Tank Fuel Pump LOW PRESSURE Lights:

Illuminated –

• Respective fuel pump switch is ON and output pressure is low.

• Respective fuel pump switch is OFF.

Extinguished –

• Respective fuel pump switch is ON and output pressure is normal.

Fuel Quantity Indicators:

• Indicates total weight of usable fuel in respective tank.

• AC standby power is required.

• Segmented arc indicates fuel quantity as a percentage of fuel capacity.

Note: There are many different types of fuel quantity indicators. The type installed in your aircraft may not necessarily match the type discussed in this presentation. The type shown here is manufactured by Simmonds®.

ERR Indicator:

• ERR appears with associated error codes (0-9) whenever a malfunction occurs.

• Used for maintenance purposes only

Fuel QTY TEST Switch:

Press and hold –

• Fuel quantity indicators display a value of “0”.

• “ERR 4” is shown.

When switch is released, a self test is initiated –

• All segments of the indicators display for two seconds.

• All segments of the indicators extinguish for two seconds.

• Indicators display full tank capacity and stored error codes, if any, for two seconds.

• Indicators return to actual fuel quantity.

Measurement/Fueling/Defueling

Fuel Measuring Stick:

• Utilized to measure fuel quantity in the No. 1 and No. 2 fuel tanks. No dripsticks associated with the center fuel tank.

Dripstick(five on each wing)

Pressure fueling station

Defueling valve

• Allows a comparison of fuel weight (as indicated by the fuel quantity indicators) to the value shown on the measuring sticks to ensure the indicators are operating normally.

• Five sticks installed on each main tank.

• Reading is obtained by turning the head of the dripstick 90° in a counter-clockwise direction. Slowly lower the stick until fuel begins to “drip” from the hole located near the bottom of the stick. Quantity may now be determined by reading the measuring units on the stick. This procedure is best performed by trained maintenance personnel.

Pressure Fueling Station:

• Provides all the necessary switches, indicators, and valves to quickly fuel all three tanks.

• Located on right wing, aft of leading edge slats.

Fueling Receptacle:

• Connects the fueling hose to the pressure fueling system.

Fueling Shutoff Valves:

• Controls fuel distribution to their respective tank.

• Electrically (DC) activated.

• Solenoid actuated, spring-loaded to the closed position.

Manual Override Push Buttons (Solenoid Override):

• Utilized if DC power is not available to the fueling shutoff valves.

• Mechanically opens shutoff valve when fuel pressure is supplied.

Fueling Power Control Switch:

Door closed –

Proximity sensor deactivates DC power to fueling valve switches and panel floodlights. Also deactivates AC power to refuel quantity indicators.

Door open –

Proximity sensor allows DC power to fueling valve switches and panel floodlights. Also allows AC power to the refuel quantity indicators.

Test Gauges and Fueling Panel:

Used by fueling personnel to coordinate the distribution of fuel to the tanks.

Right-half of pressure fueling station

Fueling Valve Switches:

OPEN –

Energizes fueling shutoff valve for respective tank.

CLOSED –

De-energizes fueling shutoff valve for respective tank.

Fueling VALVE POSITION LIGHTS:

Illuminated –

• Respective fueling valve switch in in the OPEN position and the related tank is not full.

Extinguished –

• Respective fueling valve switch in in the OPEN position and the related tank is full.

• Respective fueling valve switch is in the CLOSED position.

Refuel Quantity Indicators:

Indicates total weight of usable fuel in respective tank.

TEST GAUGES and FUELING CONTROL Switch:

(spring-loaded to OFF)

TEST GAUGES –

Checks the operation of the refuel quantity indicators by performing a self-test.

AUX POWER FUELING CONTROL –

Energizes the fueling system if the fueling power control switch should fail to operate when the fueling door is open.

Manual Defueling Valve:

Open –

Connects fuel manifold to pressure fueling station for defueling or to transfer fuel from tank to tank. Transferring of fuel from tank to tank can only be performed while the aircraft is on the ground.

Closed (picture shows handle in closed position) –

Isolates fuel manifold from pressure fueling station.

Note: The handle of the defueling valve is such that its access door cannot be closed when the defueling valve is in the open position.

Fuel Pump LOW PRESSURE Lights

The fuel pump switches normally remain in the OFF position until the pumps are needed.

With the No. 1 and No. 2 tank fuel pump switches in the OFF position, it is normal for LOW PRESSURE lights to be illuminated.

With the center tank fuel pump switches in the OFF position, it is normal for LOW PRESSURE lights to be extinguished. The reason for this is because the center tank is not always scheduled to be fueled. Therefore, the pumps are not utilized and the pump switches are selected OFF. The LOW PRESSURE lights would be a nuisance to the pilots if they were to remain illuminated with the center pump switches in the OFF position.

The following assumes all six fuel pumps are operating normally and all three tanks have been fueled:

When the No. 1 and No. 2 tank pumps are selected ON, the LOW PRESSURE lights extinguish.

When the center tank pumps are selected ON, the LOW PRESSURE lights remain extinguished.

Recall that with all six pumps operating, fuel is delivered to the engines from the center tank first.

The following scenarios will demonstrate the relationship between the fuel LOW PRESSURE lights and the master caution system.

Let’s first discuss the LOW PRESSURE lights in the center fuel tank.

Let’s assume that the center left pump has failed. Because the pump is no longer a provider of fuel pressure, the respective LOW PRESSURE light illuminates. This does not result in a MASTER CAUTION because with both center pumps ON, both LOW PRESSURE lights must be illuminated in order for the MASTER CAUTION and FUEL annunciator lights to automatically illuminate.

As a result of the center left pump failure, the No. 1 tank pumps will begin to feed the No. 1 engine. However, it is likely that the non-normal procedure will suggest opening the crossfeed valve to allow the center right pump to deplete center tank fuel. This will also help to prevent a fuel imbalance (reference your company operations manual).

If a pilot were to push either system annunciator panel, the MASTER CAUTION and FUEL annunciator would illuminate to warn the pilots of the low pressure situation in the center left pump.

Note: The system annunciator panels are also known as “recall” panels.

The master caution system may be reset by simply depressing either MASTER CAUTION – PUSH TO RESET light.

When the pilot selects the center left pump switch OFF, the LOW PRESSURE light extinguishes.

Now, let’s assume that the center right pump has failed. The respective LOW PRESSURE light illuminates. The MASTER CAUTION and FUEL annunciator lights also illuminate. With one center pump ON and one center pump OFF, the illumination of one LOW PRESSURE light will automatically illuminate the MASTER CAUTION and FUEL annunciator.

In this scenario, fuel is no longer being delivered to the engines from the center tank, and therefore the pumps in the No. 1 and No. 2 tank will automatically begin to feed the engines.

When the pilot selects the center right pump switch OFF, the LOW PRESSURE light extinguishes.


This concludes the discussion of the LOW PRESSURE lights in the center tank. The LOW PRESSURE lights in the No. 1 tank will be discussed next.

Let’s assume that the AFT pump in the No. 1 tank has failed. Because the pump is no longer a provider of fuel pressure, the respective LOW PRESSURE light illuminates. This does not result in a MASTER CAUTION because both LOW PRESSURE lights in the No. 1 fuel tank must be illuminated in order for the MASTER CAUTION and FUEL annunciator lights to automatically illuminate.

If a pilot were to push either system annunciator panel, the MASTER CAUTION and FUEL annunciator would illuminate to warn the pilots of the low pressure situation in the No. 1 tank AFT pump.


When the pilot selects the No. 1 tank AFT pump switch OFF, the LOW PRESSURE light remains illuminated.

Now, let’s assume that the FWD pump in the No. 1 tank has failed. The respective LOW PRESSURE light illuminates. The MASTER CAUTION and FUEL annunciator lights also illuminate because both LOW PRESSURE lights in the No. 1 fuel tank are illuminated.

The No. 1 engine would continue to run because the engine driven fuel pump is drawing fuel out of the No. 1 tank via the bypass valve.

When the pilot selects the No. 1 tank FWD pump switch OFF, the LOW PRESSURE light remains illuminated.


This concludes the discussion of the LOW PRESSURE lights in the No. 1 tank. The LOW PRESSURE lights in the No. 2 tank will be discussed next. You will discover that the No. 1 and No. 2 tank LOW PRESSURE lights function exactly the same.

Let’s assume that the AFT pump in the No. 2 tank has failed. Because the pump is no longer a provider of fuel pressure, the respective LOW PRESSURE light illuminates. This does not result in a MASTER CAUTION because both LOW PRESSURE lights in the No. 2 fuel tank must be illuminated in order for the MASTER CAUTION and FUEL annunciator lights to automatically illuminate.

If a pilot were to push either system annunciator panel, the MASTER CAUTION and FUEL annunciator would illuminate to warn the pilots of the low pressure situation in the No. 2 tank AFT pump.


When the pilot selects the No. 2 tank AFT pump switch OFF, the LOW PRESSURE light remains illuminated.

Now, let’s assume that the FWD pump in the No. 2 tank has failed. The respective LOW PRESSURE light illuminates. The MASTER CAUTION and FUEL annunciator lights also illuminate because both LOW PRESSURE lights in the No. 2 fuel tank are illuminated.

The No. 2 engine would continue to run because the engine driven fuel pump is drawing fuel out of the No. 2 tank via the bypass valve.

When the pilot selects the No. 2 tank FWD pump switch OFF, the LOW PRESSURE light remains illuminated.


This concludes the discussion of the LOW PRESSURE lights in the No. 2 tank.

Fuel Pump Power Sources

MAIN BUS 1MAIN BUS 1

TRANSFER BUS 1TRANSFER BUS 1 TRANSFER BUS 2TRANSFER BUS 2

MAIN BUS 2MAIN BUS 2MAIN BUS 1MAIN BUS 1

MAIN BUS 2MAIN BUS 2

Fuel Tank Capacities These figures represent the approximate amount of

useable fuel. Weight and balance calculations and the appropriate loading manual will give exact figures for your specific aircraft and condition.

Documents

FUEL SYSTEM 737-300 400