A dhc-8-200 on a test flight developed a fuel imbalance which the mechanic on board could not balanc...

Narrative:

During the maintenance check flight [we] noticed a fuel imbalance on the left tank of 200 pounds less than the one indicated on the right tank on the initial climb out. The flight crew decided to turn back and land at the airport. The unbalance increased to 400 pounds during cruise flight. We; the flight crew; decided to transfer fuel from the right to the left tank for balance purposes. The transfer process was stopped during the descent and [we] continued to monitor the fuel gauges. The fuel unbalance was stabilized at the same 400 pounds during the initial descent all the way down until the landing. We; the crew; nor the mechanic on board who was assigned to monitor the left tank during the flight noticed any leak. While on the approach tower was advised by another aircraft on the ground that while our aircraft was on short final [they] noticed something hanging or coming out from our left wing. The maintenance flight was completed unsatisfactory and the aircraft was written up for fuel unbalanced during flight.

Original NASA ASRS Text

Title: A DHC-8-200 on a test flight developed a fuel imbalance which the Mechanic on board could not balance and so on return to the airport a ground observer commented that something was hang from or coming from the left wing.

Narrative: During the Maintenance Check Flight [we] noticed a fuel imbalance on the left tank of 200 pounds less than the one indicated on the right tank on the initial climb out. The flight crew decided to turn back and land at the airport. The unbalance increased to 400 pounds during cruise flight. We; the flight crew; decided to transfer fuel from the right to the left tank for balance purposes. The transfer process was stopped during the descent and [we] continued to monitor the fuel gauges. The fuel unbalance was stabilized at the same 400 pounds during the initial descent all the way down until the landing. We; the crew; nor the Mechanic on board who was assigned to monitor the left tank during the flight noticed any leak. While on the approach Tower was advised by another aircraft on the ground that while our aircraft was on short final [they] noticed something hanging or coming out from our left wing. The maintenance flight was completed unsatisfactory and the aircraft was written up for fuel unbalanced during flight.

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	1057274
Time
Date	201212
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Dash 8-200
Operating Under FAR Part	Part 91
Flight Phase	Climb Landing Initial Climb
Flight Plan	IFR
Component
Aircraft Component	Fuel Tank
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical

A dhc-8-200 on a test flight developed a fuel imbalance which the mechanic on board could not balance and so on return to the airport a ground observer commented that something was hang from or coming from the left wing.