Narrative:

Pilot's write-up in log book: 'on approach for runway, left propeller np transitioned 120% after retarding power lever to stops. Airspeed was 250 pushed power levers up slightly and it returned to normal right propeller ok.' upon trying to evaluate what maintenance action to take several questions came to mind: 1) was there any other aircraft in the landing zone? 2) how fast was the power levers retarded to the stops? 3) were the left and right power levers retarded at the same time? 4) did the left power lever miss the stop and attempt to go into reverse? 5) did the aircraft yaw or go into an unusual attitude to indicate to the pilot that a problem existed? 6) how long was the transit np encountered? 7) were there any other abnormal indications or any other gauges? After researching all available material for maintenance corrective action, a certified mechanic ground ran the aircraft. All checks in the aircraft maintenance manual concerning np limits was performed. Maximum np was to mfr's specifications. Aircraft was approved for return to service. Further investigation revealed np above 110% for any period of time requires a more detailed inspection of components. Aircraft is now grounded pending further investigation. Supplemental information from acn 110542: after a careful visibility inspection of the left propeller, I row the left engine propeller through several tests to try and duplicate an overspd condition. Those tests included: 1) np governing range operational check. 2) minimum governing np operational check. 3) maximum np operational check. All tests were performed as per MM 61-00-00, pages 501-504. 4) overspd governor operational check was also performed as per md #9. All np and torque valves, for these tests, were within mfr's limitations. Inspection of the propeller control system as per sb 120-061-0009 was also done. The system successfully passed this inspection procedure also. Tests 1-4 were performed 3 times to the left engine propeller each time indicating normal operation. I then performed tests 1-4 on the right engine as to compare results. Everything appeared normal. No excessive vibrations or abnormal indications were observed throughout testing. With the manuals I had I felt that I had thoroughly tested the system and signed the log book as such.

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Original NASA ASRS Text

Title: MAINTENANCE PERSONNEL REPORT ON WHAT WAS DONE TO CORRECT A LOG BOOK WRITE-UP OF OVERSPEEDING PROPELLER ON TURBO PROPELLER ENGINE.

Narrative: PLT'S WRITE-UP IN LOG BOOK: 'ON APCH FOR RWY, LEFT PROP NP TRANSITIONED 120% AFTER RETARDING PWR LEVER TO STOPS. AIRSPD WAS 250 PUSHED PWR LEVERS UP SLIGHTLY AND IT RETURNED TO NORMAL RIGHT PROP OK.' UPON TRYING TO EVALUATE WHAT MAINT ACTION TO TAKE SEVERAL QUESTIONS CAME TO MIND: 1) WAS THERE ANY OTHER ACFT IN THE LNDG ZONE? 2) HOW FAST WAS THE PWR LEVERS RETARDED TO THE STOPS? 3) WERE THE LEFT AND RIGHT PWR LEVERS RETARDED AT THE SAME TIME? 4) DID THE LEFT PWR LEVER MISS THE STOP AND ATTEMPT TO GO INTO REVERSE? 5) DID THE ACFT YAW OR GO INTO AN UNUSUAL ATTITUDE TO INDICATE TO THE PLT THAT A PROB EXISTED? 6) HOW LONG WAS THE TRANSIT NP ENCOUNTERED? 7) WERE THERE ANY OTHER ABNORMAL INDICATIONS OR ANY OTHER GAUGES? AFTER RESEARCHING ALL AVAILABLE MATERIAL FOR MAINT CORRECTIVE ACTION, A CERTIFIED MECH GND RAN THE ACFT. ALL CHKS IN THE ACFT MAINT MANUAL CONCERNING NP LIMITS WAS PERFORMED. MAX NP WAS TO MFR'S SPECS. ACFT WAS APPROVED FOR RETURN TO SVC. FURTHER INVESTIGATION REVEALED NP ABOVE 110% FOR ANY PERIOD OF TIME REQUIRES A MORE DETAILED INSPECTION OF COMPONENTS. ACFT IS NOW GNDED PENDING FURTHER INVESTIGATION. SUPPLEMENTAL INFO FROM ACN 110542: AFTER A CAREFUL VIS INSPECTION OF THE LEFT PROP, I ROW THE LEFT ENG PROP THROUGH SEVERAL TESTS TO TRY AND DUPLICATE AN OVERSPD CONDITION. THOSE TESTS INCLUDED: 1) NP GOVERNING RANGE OPERATIONAL CHK. 2) MINIMUM GOVERNING NP OPERATIONAL CHK. 3) MAX NP OPERATIONAL CHK. ALL TESTS WERE PERFORMED AS PER MM 61-00-00, PAGES 501-504. 4) OVERSPD GOVERNOR OPERATIONAL CHK WAS ALSO PERFORMED AS PER MD #9. ALL NP AND TORQUE VALVES, FOR THESE TESTS, WERE WITHIN MFR'S LIMITATIONS. INSPECTION OF THE PROP CTL SYS AS PER SB 120-061-0009 WAS ALSO DONE. THE SYS SUCCESSFULLY PASSED THIS INSPECTION PROC ALSO. TESTS 1-4 WERE PERFORMED 3 TIMES TO THE LEFT ENG PROP EACH TIME INDICATING NORMAL OPERATION. I THEN PERFORMED TESTS 1-4 ON THE RIGHT ENG AS TO COMPARE RESULTS. EVERYTHING APPEARED NORMAL. NO EXCESSIVE VIBRATIONS OR ABNORMAL INDICATIONS WERE OBSERVED THROUGHOUT TESTING. WITH THE MANUALS I HAD I FELT THAT I HAD THOROUGHLY TESTED THE SYS AND SIGNED THE LOG BOOK AS SUCH.

Data retrieved from NASA's ASRS site as of August 2007 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.