Narrative:

After a normal takeoff; at approximately 1;000 feet; the first officer and I noticed a slight vibration. At 1;500 feet when we set climb power to 1;050 RPM the vibration increased. At that point we decided to try 900 RPM to see if that would reduce the vibration; but the vibration seemed to increase. We determined that this was not a normal vibration and that it was continuing to worsen. We told ATC that we would need to return for landing. As we turned for a right downwind the vibration increased so much that the control yoke was actually shaking in my hands. The first officer called the flight attendant and cabin to notify them of our return. We lowered the landing gear and flaps. As we turned base the vibration had increased to the point that we decided to declare an emergency. We could not determine which engine was causing the vibration but noticed the number one engine torque did fluctuate about 10%. All other engine indications were normal. The landing was normal with no control problems. We taxied to the gate and safely deplaned the passengers. After maintenance inspected the aircraft they determined that the number 3 prop blade bearing race on the number one engine was bad; causing the extreme prop vibration.

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Original NASA ASRS Text

Title: Dash 8 Captain reported significant vibration after takeoff so the flight returned to departure airport; where a bad propeller blade bearing race was found.

Narrative: After a normal takeoff; at approximately 1;000 feet; the First Officer and I noticed a slight vibration. At 1;500 feet when we set climb power to 1;050 RPM the vibration increased. At that point we decided to try 900 RPM to see if that would reduce the vibration; but the vibration seemed to increase. We determined that this was not a normal vibration and that it was continuing to worsen. We told ATC that we would need to return for landing. As we turned for a right downwind the vibration increased so much that the control yoke was actually shaking in my hands. The First Officer called the Flight Attendant and cabin to notify them of our return. We lowered the landing gear and flaps. As we turned base the vibration had increased to the point that we decided to declare an emergency. We could not determine which engine was causing the vibration but noticed the number one engine torque did fluctuate about 10%. All other engine indications were normal. The landing was normal with no control problems. We taxied to the gate and safely deplaned the passengers. After Maintenance inspected the aircraft they determined that the Number 3 prop blade bearing race on the Number one engine was bad; causing the extreme prop vibration.

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.