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Air Refueling System Print E-mail
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Written by Sabc   
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air_refueling_imageThe F-15E Strike Eagle can be refueled during flight via a fixed boom system (Air Force type). The boom receptacle is embedded in the left wing root at the the leading edge of the wing (see figure below).

argaiv1941

air_refueling_system

1
2
- Air refueling door actuator
- Air refueling door (open)
3
4
- Refueling pipe
- Fuselage tank

The air refueling door (2) is normally closed during flight and is marked by a painted white frame around it. During air refueling a hydraulic actuator (1) opens the door and reveals the air refueling receptacle bay illuminated by two slipway lights and a receptacle flood light (to aid night refuelings). The fixed boom slides into the receptacle and locks there and fuel is transferred via the refueling pipe (3) into the internal fuselage tanks (4).

Air refueling is a pressure driven process, which means that fuel is transferred into the Strike Eagle's fuel tanks by higher fuel pressure generated by the tanker aircraft. To keep the aircraft's center of gravity within safe limits, a float switch in tank 1 prevents external drop tank refueling until fuel level in tank 1 exceeds approximately 1,560 pounds. Conformal fuel tanks start to fill immediately, regardless of this float switch. In case of CFT's, center of gravity is kept within limits by the sequence by which CFT compartments are filled.

There is an air refuel pressure switch, which activates when fuel pressure exceeds approximately 80 PSI. Once activated the system automatically disconnects the refueling boom, thus preventing the aircraft's fuel system to become over-pressurized during air refueling.

Pilot Controls

The aircraft's fuel management systems can be controlled by switches on the fuel panel, located forward on the pilot left side console (see figure below). The switches and their functions are discussed below.

internal_fuel_panel

1
2
3
- Fuel control switch: external wing tanks
- Fuel control switch: centerline tank
- Fuel control switch: conformal tank
4
5
6
7
- Fuel dump switch
- CFT emergency transfer switch
- External transfer switch
- Slipway switch

The three fuel control switches (1, 2, 3) control transfer nd refuel procedures of all external tank types: external wing tanks (WING), centerline tank (CTR) and conformal fuel tanks (CFT). Their transfer functions are discussed in details in article External Fuel Tanks. During air refueling these switches provide an option to refuel external drop tanks and/or CFT's. If a switch is in NORM position, its respective tank will be refilled during air refueling. If a switch is in STOP REFUEL position, its respective tank will not be refilled.

The fuel dump switch (4) is used to dump fuel. Its functions are discussed in details in article Fuel Dumping System.

The CFT emergency transfer switch (5) is used in emergency situations to transfer CFT fuel. Its functions are discussed in details in article Conformal Fuel Tanks.

The external transfer switch (6) is used to schedule external fuel transfer. Its functions are discussed in details in article External Fuel Tanks.

The slipway switch (7) controls the aerial refueling receptacle door. It has the following three positions:

CLOSE: Putting the switch into this position closes the slipway door, turns on tank 1 and CFT transfer pump(s), reestablishes external fuel tank pressurization, and fuel sequencing.

OPEN: Putting the switch into this position shuts off tank 1 transfer pump, CFT transfer pumps (if operating), and opens the slipway door. Once the slipway door is opened, it depressurizes the external fuel tanks (if there is no FUEL LOW condition), turns on the receptacle lights, and turns on the READY light indicating the system is ready for boom engagement.

ORIDE: Putting the switch into this position Accomplishes the same functions as putting it into OPEN position, plus a couple of other functions. This position allows boom locking, but the tanker disengage feature (both automatic and manual) is lost. With the slipway sitch in ORIDE, the Strike Eagle aircrew must initiate all disconnects. ORIDE mode bypasses tank 1 float switch (see above) and external tanks may be refueled regardless of the fuel level in tank 1.

Note when the slipway door is open, the external tanks are depressurized, hence descent rate should not exceed 10,000 feet per minute. To prevent aircarft center of gravity to move outside safe limits when using ORIDE position, then STOP REFUEL should be selected by the fuel control switches until tank 1 fuel quantity rises above 1,560 pounds. FUEL LOW caution activation will not activate tank 1 transfer pump if the slipway door is open.

The pilot can disconnect the boom from the receptacle by pressing the auto acquisition button on the flight control stick (see article Pilot Flight Control Stick).

If the slipway cannot be opened by normal procedures, there is an emergency procedure to open it for refueling. This emergency procedure is initiated by putting the emergency refuel switch (located on the pilot left console, behind the throttle quadrant at the base of the left cockpit wall) into its OPEN position. Once there, pyrotechnic devices (powered by the aircraft's emergency essentiel 28 V dc bus) open the slipway door, which cannot then be closed in flight. Normaly slipway lighting will be available, but the READY light will not go out during refueling, not will the boom lock in the receptacle. External fuel tank pressurization can be restored by placing the slipway door switch to close.

Sources

  • F-15E Flight Manual (TO 1F-15E-1) C 15 August 1990, courtesy of eFlightManuals

Forum Discussion

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Last Updated on Wednesday, 08 September 2010
 


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