A B737-800 left fuel tank contained 2;000 pounds less than the right tank at takeoff. The fuel imbal...

Narrative:

We did not notice until airborne that we took off with a 2;000 pound main tank fuel imbalance. While hand flying the departure as the pilot flying; I made a comment about the aircraft requiring a lot of left trim. The pilot not flying looked down to see an amber fuel imbalance indication and the left fuel tank showing 2;000 pounds less than the right. Tot: 20.0 left: 6.5 right: 8.5 center: 5.0. All fuel pumps verified on. Crossfeed verified closed. I engaged the autopilot and we ran the QRH fuel imbalance checklist. Imbalance corrected.when checking fuel quantity on the ground; double check each fuel tank; not just the total fuel on board which agreed with our required fuel. The amber light does not illuminate until airborne; so we can't rely on it to detect a main tank imbalance on the ground.

Original NASA ASRS Text

Title: A B737-800 Left Fuel tank contained 2;000 LBS less than the Right Tank at takeoff. The FUEL IMBALANCE annunciator does not illuminate unless the aircraft is airborne; the crew missed the imbalance during preflight.

Narrative: We did not notice until airborne that we took off with a 2;000 LB main tank fuel imbalance. While hand flying the departure as the pilot flying; I made a comment about the aircraft requiring a lot of left trim. The pilot not flying looked down to see an amber FUEL IMBALANCE indication and the left fuel tank showing 2;000 LBS less than the right. TOT: 20.0 LEFT: 6.5 RIGHT: 8.5 CTR: 5.0. All fuel pumps verified on. Crossfeed verified closed. I engaged the autopilot and we ran the QRH fuel imbalance checklist. Imbalance corrected.When checking fuel quantity on the ground; double check each fuel tank; not just the total fuel on board which agreed with our required fuel. The amber light does NOT illuminate until airborne; so we can't rely on it to detect a main tank imbalance on the ground.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1116863
Time
Date	201309
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Plan	IFR
Component
Aircraft Component	Fuel System
Person 1
Function	Pilot Flying
Events
Anomaly	Deviation - Procedural FAR Deviation - Procedural Published Material / Policy

A B737-800 left fuel tank contained 2;000 pounds less than the right tank at takeoff. The fuel imbalance annunciator does not illuminate unless the aircraft is airborne; the crew missed the imbalance during preflight.