An SF340 returned to the departure airport due to fluctuating prop RPM on the right engine.

Attributes
ACN	867037
Time
Date	201001
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	SF 340B
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Engine
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 22 Flight Crew Total 6500 Flight Crew Type 5000
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Commercial
Experience	Flight Crew Last 90 Days 22 Flight Crew Total 3300 Flight Crew Type 300
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

During climb to 17;000 feet the first officer noticed subtle propeller fluctuations. Continued to monitor engine instruments. Initially thought it was a gauge problem. Approximately 5-10 minutes later; prop RPM fluctuation was more pronounced. Propeller rpms fluctuated below 1040 causing a surge in torque. Completed the emergency non normal checklist for erratic/uncommanded engine. Torque motor was locked out which caused the power surges to subside. Maintenance and dispatch were notified. It was decided to return to our departure airport for a normal landing. No emergency declared. Torque motor was locked out on other engine prior to landing as suggested in the checklist.

Original NASA ASRS Text

Title: An SF340 returned to the departure airport due to fluctuating prop RPM on the right engine.

Narrative: During climb to 17;000 feet the First Officer noticed subtle propeller fluctuations. Continued to monitor engine instruments. Initially thought it was a gauge problem. Approximately 5-10 minutes later; prop RPM fluctuation was more pronounced. Propeller RPMs fluctuated below 1040 causing a surge in torque. Completed the Emergency Non Normal checklist for erratic/uncommanded engine. Torque motor was locked out which caused the power surges to subside. Maintenance and Dispatch were notified. It was decided to return to our departure airport for a normal landing. No emergency declared. Torque motor was locked out on other engine prior to landing as suggested in the checklist.

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.