The center tank pumps are set to give a higher pressure of fuel than the
related wing tank pumps. A sequence valve (installed on each wing tank
pump canister) reduces the output pressure of the related wing tank pump.
When all the pumps operate, the center tank pump will supply fuel to its
related engine.
When the wing tank pumps are set to ON, the pumps will operate
continuously during the flight until switched off manually.
The center tank pumps have two modes of operation, manual and automatic.
The MODE SEL P/BSW (48QA), on the FUEL panel (40VU), controls these modes
of operation.
In manual mode (MODE SEL P/BSW released out), the operation of the center
tank pumps is controlled by the CTR TK PUMPS 1 and 2 P/BSWs (33QA and
34QA).
In automatic mode (MODE SEL P/BSW pushed in), and with the CTR TK PUMPS 1
and 2 P/BSWs set to ON:
-
the center tank pumps are set to on and off automatically during specified flight phases
-
the center tank pumps will supply fuel to the engines, as required,
when the fuel is at specified levels (Ref. 28-46-00). At engine start-up, the automatic fuel feed system operates as follows:
-a signal from the interface units (1KS1 and 1KS2) energizes the center tank control relays (51QA, 52QA)
-the AUTO CTL relays (41QA, 42QA) are de-energized
-if the center tank LOW LVL sensors are wet with fuel the two center tank pumps operate
-two minutes after the first engine reaches idle speed, the center tank pumps stop
-
if the second engine is started during the two minutes, the center tank pumps will operate for two more minutes. They will operate for two more minutes from when the second engine reaches idle speed and then stop
-
if the second engine is started after the two minutes are over, the center tank pumps will operate again for two minutes. They will operate from the time that the second engine reaches idle speed
-
the position of the slats now controls the operation of the center tank pumps
-
the center tank pumps will not operate again until the slats are retracted
-until then the wing tank pumps supply fuel to the engines.
After take-off, the automatic fuel feed system operates as follows:
-the AUTO CTL relays (41QA and 42QA) de-energize when the slats retract
R 1EFF : 001-049, 051-099, 101-149, 151-199, 1 28-21-00Page 55 1201-299, 401-499, 1Aug 01/05 1 1 1CES 1
-the center tank pump control relays (35QA and 36QA) energize and the center tank pumps are given signals to operate, independently of each other
-
a center tank pump will stop when the two FULL LVL sensors in the related wing tank are wet. The pump will not operate again until at least one UNDERFULL LVL sensor in the related wing tank is dry. The related center tank LOW LVL sensor must also be wet for the pump to restart
-
a signal is given to the time delay relays (45QA and 46QA) when a center tank LOW LVL sensor becomes dry. When the LOW LVL sensor has been dry for five minutes, the related center tank pump is latched off
-the latch is released and the related pump(s) come on when MANUAL mode is selected or when the refuel panel access door is opened
-FAULT INHIBIT relays do not let the FAULT annunciators come ON during the five minute cycle
-when a center tank pump stops, an engine is supplied with fuel from the related wing tank pumps.
**ON A/C ALL
In the electrical smoke configuration (Ref. 24-24-00) the contactor 17QA is de-energized. The L (R) TK PUMP 1 P/BSW then connects a 28VDC supply to the contactor 53QA (No. 1 fuel pump emergency contactor-control). The contactor 53QA connects a 115VAC supply to energize the fuel pump 21QA (22QA).
R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 401-499,
The pumps get their fuel supply from the lowest part of the collector cell. When they are in operation each pump gives two outputs. One output is to the engine feed pipe, one to the related scavenge jet pump.
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