Return to article

 
Model Message Fuel quantity condition (difference) Comments
737-600/
-700/-800/
-900
IMBAL
(Discrete amber light on round-dial quantity indicator)
1,000 lb (450 kg) or more between main tanks Illuminated amber at difference >1,000 lb (450 kg). Displayed below main tank with lower fuel quantity. Fuel quantity arc and digits on tank with lower fuel quantity turn amber. Inhibited when airplane on ground. Inhibited by fuel LOW indication when both indications exist. Displayed until imbalance decreases to 200 lb (90 kg).
747-400

FUEL IMBAL 1-4
(EICAS advisory message)

FUEL IMBAL 2-3
(EICAS advisory message)

3,000 lb (1,360 kg) or more between main tanks 1 and 4

6,000 lb (2,720 kg) or more between main tanks 2 and 3

Message no longer displayed at difference <1,000 lb (450 kg).


Message no longer displayed at difference <1,000 lb (450 kg). This condition has been observed to occur on long sectors when fuel is being supplied from main tanks 2 and 3 to all engines.

757 FUEL CONFIG
(EICAS advisory message)
Approximately 2,000 lb (900 kg) or more between main tanks Both center pumps switched off with usable fuel remaining in center tank (approximately 1,000 lb [450 kg]) or left and right fuel tank quantities differ by approximately 2,000 lb (900 kg). Inhibited by LOW FUEL indication.
767 FUEL CONFIG
(EICAS advisory message/light)
Approximately 2,000 lb (900 kg) or more between main tanks Both center pumps switched off with usable fuel remaining in center tank (approximately 1,000 lb [450 kg]) or left and right fuel tank quantities differ by approximately 2,000 lb (900 kg). Inhibited by LOW FUEL indication.
777 FUEL IMBALANCE (EICAS advisory message) Main tank quantities differ by a predetermined amount (see comments) Fuel imbalance will be set when difference between main tanks exceeds allowable quantity at >30 sec. Allowable quantity is 4,000 lb (1,800 kg) when total main tank fuel is 45,000 lb (20,450 kg) or less (50,000 lb [22,725 kg] or less for 777-200 Increased Gross Weight [IGW] and 777-300), with a linear reduction to 2,000 lb (900 kg) when total main tank fuel is 111,000 lb (50,450 kg) (114,000 lb [51,800 kg] for 777-200 IGW and 777-300). Message signal will remain set until imbalance decreases 200 lb (90 kg) below set quantity at >15 sec.
MD-11 LAT FUEL UNBAL
(Alert message)
4,000 lb (1,800 kg) or more between tanks 1 and 3  
MD-90 LAT FUEL UNBAL
(Alert message)
1,500 lb (675 kg) or more between right and left tanks Alert is a customer option on some airplanes.

Table 1. FUEL IMBALANCE INDICATIONS.

| Boeing Home | Boeing Commercial |
Aero Copyright © The Boeing Company. All rights reserved.