Narrative:

During climb out we experienced two loud and hard compressor stalls on the #2 engine. The preflight; taxi and takeoff were all normal. Passing through FL220 we experienced the first compressor stall; it sounded and felt like something had fallen in the main cargo deck; but we knew the cargo holds were empty. As we passed through FL250 we experienced the second compressor stall; this one was much louder and harder. On this second compressor stall; we were paying close attention to the eids [engine instruments display system] and noticed corresponding spikes in both N1 and egt for the #2 engine. As this had been the main cause for the original maintenance delay; we were quite sure that the problem still existed. We contacted ATC and requested to stop our climb at FL260. We followed the check list and discovered that the engine was no longer compressor stalling at a lower power setting (i.e.; a recoverable stall) and then contacted maintenance control who asked that we return to our departure airport for further engine evaluation. I advised dispatch we would be returning and then relayed our request to ATC. The descent; approach; landing and taxi in were all normal. Then engine performed normally through all of the last phases of flight although we never needed to use more than cruise/descent power. All normal and abnormal checklists were followed throughout the flight and for our uneventful return. While we had not declared an emergency with ATC they did have the equipment standing by for our landing but; after our normal landing and roll out; they returned to the station.

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Original NASA ASRS Text

Title: A B747-200 flight crew; after collaboration with Maintenance Control and Dispatch; elected to return to their departure airport after experiencing two 'loud and hard' compressor stalls on the number two engine during climb out.

Narrative: During climb out we experienced two loud and hard compressor stalls on the #2 engine. The preflight; taxi and takeoff were all normal. Passing through FL220 we experienced the first compressor stall; it sounded and felt like something had fallen in the main cargo deck; but we knew the cargo holds were empty. As we passed through FL250 we experienced the second compressor stall; this one was much louder and harder. On this second compressor stall; we were paying close attention to the EIDS [Engine Instruments Display System] and noticed corresponding spikes in both N1 and EGT for the #2 engine. As this had been the main cause for the original maintenance delay; we were quite sure that the problem still existed. We contacted ATC and requested to stop our climb at FL260. We followed the check list and discovered that the engine was no longer compressor stalling at a lower power setting (i.e.; a recoverable stall) and then contacted Maintenance Control who asked that we return to our departure airport for further engine evaluation. I advised Dispatch we would be returning and then relayed our request to ATC. The descent; approach; landing and taxi in were all normal. Then engine performed normally through all of the last phases of flight although we never needed to use more than cruise/descent power. All normal and abnormal checklists were followed throughout the flight and for our uneventful return. While we had NOT declared an emergency with ATC they did have the equipment standing by for our landing but; after our normal landing and roll out; they returned to the station.

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.