Narrative:

The light transport aircraft type has an electrical engine control system which can cause engine surges if a failure of the system occurs, additionally, propeller overspds have been experienced by several operators of the light transport resulting in engine failures and specific procedures have been established for implementation in case of an overspd occurrence. On 12-90 flight was climbing through 4400' MSL when the left engine began surging and the propeller became unstable plus or minus 5 percent this could have resulted in an overspd and I reduced power immediately and increased pitch in order to slow the airplane down as per flight manual procedures. The engine control was turned off and the engine became stable, and propeller speed was normal. After a few mins of checking, it was determined that the propeller was ok and flight was continued, engine surges were reported to company maintenance. During the engine surges and overspd maneuver, altitude went from 5000' to 5200', since 5000' was the assigned altitude, ATC commented as to our assigned altitude. By then I had the engine problem corrected and was level at 5000'. The altitude deviation was a result of having to pitch up to slow the aircraft per approved procedures.

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Original NASA ASRS Text

Title: COMMUTER LTT ALT DEVIATION EXCURSION FROM CRUISE ALT TO REDUCE AIRSPEED. SPEED REDUCTION IS PART OF CHECKLIST PROC THAT WAS BEING USED TO CORRECT ENGINE SURGING THAT HAD RESULTED IN ENGINE OVERSPEEDING ON THIS TYPE ACFT.

Narrative: THE LTT ACFT TYPE HAS AN ELECTRICAL ENG CTL SYS WHICH CAN CAUSE ENG SURGES IF A FAILURE OF THE SYS OCCURS, ADDITIONALLY, PROP OVERSPDS HAVE BEEN EXPERIENCED BY SEVERAL OPERATORS OF THE LTT RESULTING IN ENG FAILURES AND SPECIFIC PROCS HAVE BEEN ESTABLISHED FOR IMPLEMENTATION IN CASE OF AN OVERSPD OCCURRENCE. ON 12-90 FLT WAS CLBING THROUGH 4400' MSL WHEN THE L ENG BEGAN SURGING AND THE PROP BECAME UNSTABLE PLUS OR MINUS 5 PERCENT THIS COULD HAVE RESULTED IN AN OVERSPD AND I REDUCED PWR IMMEDIATELY AND INCREASED PITCH IN ORDER TO SLOW THE AIRPLANE DOWN AS PER FLT MANUAL PROCS. THE ENG CTL WAS TURNED OFF AND THE ENG BECAME STABLE, AND PROP SPD WAS NORMAL. AFTER A FEW MINS OF CHKING, IT WAS DETERMINED THAT THE PROP WAS OK AND FLT WAS CONTINUED, ENG SURGES WERE RPTED TO COMPANY MAINT. DURING THE ENG SURGES AND OVERSPD MANEUVER, ALT WENT FROM 5000' TO 5200', SINCE 5000' WAS THE ASSIGNED ALT, ATC COMMENTED AS TO OUR ASSIGNED ALT. BY THEN I HAD THE ENG PROB CORRECTED AND WAS LEVEL AT 5000'. THE ALT DEV WAS A RESULT OF HAVING TO PITCH UP TO SLOW THE ACFT PER APPROVED PROCS.

Data retrieved from NASA's ASRS site as of July 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.