When the center-tank low-level-sensor (21QJ,22QJ) is dry for more than 5 minutes, the related center-tank pump control valve will close. If, during the 5 minutes the sensor becomes wet, for a minimium of 11 seconds, the center-tank pump control valve will stay open. The control valve will stay open until the sensor is continuously dry for five more minutes.
 1EFF : ALL 1 28-46-00Page 42 1 1 Aug 01/05 1 1 1CES 1 When the wing low-level sensors 15QJ and 40QJ are dry for 30 seconds continuously, a 1500kg (3300lb) LO LEVEL warning is shown on the ECAM display unit. When the wing low-level sensors 16QJ and 39QJ are dry for 30 seconds continuously, a 750kg (1650lb) LO LEVEL warning is shown on the ECAM display unit.

 **ON A/C ALL
 When the IDG shut-off sensor 38QJ is dry the FLSCU signals the fuel return valve to close. This stops the fuel recirculation system (Ref. 28-16-00), to prevent an increase in the amount of unusable fuel in the wing-tank.

R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 401-499,
 C. Full and Underfull Level Sensing
 (Ref. Fig. 005)

 The full level sensors, 23QJ, 27QJ and the underfull level sensors 24QJ, 25QJ and 26QJ, are used to control the automatic operation of the center tank fuel pumps. When any one of the full level and the related underfull level sensors become dry, the FLSCU signals the related center tank fuel pump to operate. When the full-level sensor becomes wet again the FLSCU signals the related center tank fuel pump to stop. The difference between the full and the underfull level-sensors is equal to a fuel quantity of 500 kg (1100 lb).
 **ON A/C 301-399,
 C. Full and Underfull Level Sensing (Ref. Fig. 005A) The full level sensors, (23QJ, 27QJ), and the underfull level sensors, (24QJ, 25QJ and 26QJ), monitor the fuel transfer to the wing from the center-tank jet-pumps. When one of the full level and the related underfull level sensors become dry, the FLSCU signals the center-tank jet-pump control-valve to open. When the full-level sensor becomes wet again the FLSCU signals the control valve to close. The difference between the full and the underfull level-sensors is equal to a fuel quantity of 200kg (440 lb).
 1EFF : ALL 1 28-46-00Page 43 1 1 Aug 01/05 1 1 1CES 1 **ON A/C ALL

 D. Overflow Level Sensing

R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 401-499,
 (Ref. Fig. 004)
 **ON A/C 301-399,
 (Ref. Fig. 004A)
 **ON A/C ALL
 If fuel from the wing tank overflows into the vent surge tank, the FLSCUs signal the Engine Interface Unit (EIU) (Ref. 73-20-00) to close the fuel return-valve.
 **ON A/C 301-399,
 If an overflow sensor becomes wet, the FLSCUs will send a signal to:
 -
the annunciator light test and dimming system (Ref. 33-14-00). This system will signal the related CTR TK XFR pump pushbutton switch (5QL, 6QL) (Ref. 28-26-00) FAULT annunciator to come on

 -
the ECAM Engine/Warning Display (EWD) to show the warning FUEL - L(R) WING TK OVERFLOW

 -
the FADEC to close the FRV and thus stop the recirculation system (Ref. 28-16-00).

 **ON A/C ALL
 E. Temperature Sensing
R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 401-499,
 (Ref. Fig. 004)
 1EFF : ALL 1 28-46-00Page 44 1 1 Aug 01/05 1 1 1CES 1 **ON A/C 301-399,

 (Ref. Fig. 004A)
 **ON A/C ALL
 The system has temperature sensors, the electrical resistance of which changes with the temperature of the adjacent fuel. The FLSCU measures the value of the current from the sensor and compares it to a specified value.
R **ON A/C 001-049, 051-099, 101-149, 151-199, 201-299, 401-499,
 In flight, the FLSCU signals the EIU (Ref. 73-20-00) to close the FRV when:
 -
the temperature of the fuel in the wing tank inner cell is more than

 52.5 deg. C.

 -
the temperature of the fuel in the wing tank outer cell is more than 55 deg. C. This keeps the fuel temperature in limits.

 NOTE : On the ground, the signal from the FLSCU to close the FRV may be
____ overridden by the EIU (depending on engine type) . If the temperature of the fuel is high, the FWC (on the ECAM display) will show warnings (Ref. 28-40-00).
 **ON A/C 301-399,
 In flight, the FLSCU signals the EIU (Ref. 73-20-00) to close the FRV when the temperature of the fuel in the wing is more than 52.5 deg. C. This keeps the fuel temperature in limits.
 NOTE : On the ground, the signal from the FLSCU to close the FRV is
____ overridden by the EIU. If the temperature of the fuel is high, the FWC (on the ECAM display) will show warnings (Ref. 28-40-00).
　
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