Narrative:

Maintenance met us at the aircraft and we discovered the aircraft had an open write-up for low prop RPM and fluctuation during takeoff/climbout. It was noted that once the condition levers were brought back to 1050; the fluctuation stopped. Maintenance performed the beta lockout deactivation procedure; and we then started the engines and cooperated with maintenance to perform the warning horn operational verification as outlined in the MEL. Once this was completed; maintenance signed off the aircraft; we boarded and departed the gate. Upon taking the runway; the captain (pilot flying) held the brakes and advanced the power levers then commenced the takeoff roll. Throughout the takeoff roll; the #1 prop RPM was reading approximately 1186 while #2 was around 1208. Both torque indications were steady and within limits. After rotation; the #1 torque began to fluctuate between 74% and 90%. #1 prop RPM remained steady; but lower than usual around 1170. We noticed the aircraft yawing slightly back and forth due to differential power. Once we raised the flaps and brought the condition levers back to 1050 for climbout; the torque fluctuation ceased and everything returned to normal. We decided to return as a precaution; since we would not have maximum power available on the #1 engine. I contacted operations; advised them of our decision to return; and made a PA. We were vectored for a visual approach and landed uneventfully. We deplaned at the gate; and the captain made another writeup. The maintenance action taken to troubleshoot the problem was ineffective.

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Original NASA ASRS Text

Title: Dash 8 Flight Crew is dispatched with the Beta Lockout deactivated due to a log book write up for fluctuating torque on the number 1 engine. Problem reoccurs after takeoff and flight returns to departure airport.

Narrative: Maintenance met us at the aircraft and we discovered the aircraft had an open write-up for low prop RPM and fluctuation during takeoff/climbout. It was noted that once the condition levers were brought back to 1050; the fluctuation stopped. Maintenance performed the Beta Lockout Deactivation Procedure; and we then started the engines and cooperated with maintenance to perform the Warning Horn Operational Verification as outlined in the MEL. Once this was completed; maintenance signed off the aircraft; we boarded and departed the gate. Upon taking the runway; the Captain (pilot flying) held the brakes and advanced the power levers then commenced the takeoff roll. Throughout the takeoff roll; the #1 prop RPM was reading approximately 1186 while #2 was around 1208. Both torque indications were steady and within limits. After rotation; the #1 torque began to fluctuate between 74% and 90%. #1 prop RPM remained steady; but lower than usual around 1170. We noticed the aircraft yawing slightly back and forth due to differential power. Once we raised the flaps and brought the condition levers back to 1050 for climbout; the torque fluctuation ceased and everything returned to normal. We decided to return as a precaution; since we would not have maximum power available on the #1 engine. I contacted Operations; advised them of our decision to return; and made a PA. We were vectored for a visual approach and landed uneventfully. We deplaned at the gate; and the Captain made another writeup. The maintenance action taken to troubleshoot the problem was ineffective.

Data retrieved from NASA's ASRS site as of April 2012 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.