Narrative:

Climbing out night VFR after cleanup (approx. 7000 feet) we heard loud bangs coming from the aircraft. No obvious signs of engine issues; but we had just turned the air driven pump (adp) off as per procedure with auto mode inoperative. I reduced engine power slightly and captain returned pump to on position. Banging stopped and we and returned to the departure airport. Engines operated normally for return and landing. After inspection by airport rescue and fire fighting (arff) we taxied to gate.looking back on it now; there's not a whole lot I would have done differently. I didn't go crazy pulling throttles and turning things off since there were no obvious signs where the problem was coming from. Very calmly slightly reduced power on both engines but slightly more on the left since that was my guess as to where the banging was coming from. Total reduction was probably no more than 10 percent N1 when banging stopped. The only mistake I made was probably unrelated to the whole incident. On climb out after clean and 250 I selected climb 2 since we were only cleared to 14;000 feet and were climbing at 4800 FPM at such a light weight. Later on; I realized this procedure only applies to our 757 fleet and not the 767. Since I've been flying the 757 much more I guess it was just a habit. I will go back and review my 767 procedural differences more often and do a better job with confirming with the other pilot what I'm doing. Also; [there have been recent changes in procedures]. I've been on the airplane for about 10 years now and procedures have been in a constant state of change as long as I can remember. Hopefully that will all get resolved soon as well.overall it went well. Approach and arff were excellent and helped us out the entire time. Very professional and well done!

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Original NASA ASRS Text

Title: During climbout; a B767 developed a loud banging sound which the crew could not positively identify; but suspected an engine because a power reduction stopped the noise.

Narrative: Climbing out night VFR after cleanup (approx. 7000 feet) we heard loud bangs coming from the aircraft. No obvious signs of engine issues; but we had just turned the Air Driven Pump (ADP) off as per procedure with auto mode inoperative. I reduced engine power slightly and Captain returned pump to on position. Banging stopped and we and returned to the departure airport. Engines operated normally for return and landing. After inspection by Airport Rescue and Fire Fighting (ARFF) we taxied to gate.Looking back on it now; there's not a whole lot I would have done differently. I didn't go crazy pulling throttles and turning things off since there were no obvious signs where the problem was coming from. Very calmly slightly reduced power on both engines but slightly more on the left since that was my guess as to where the banging was coming from. Total reduction was probably no more than 10 percent N1 when banging stopped. The only mistake I made was probably unrelated to the whole incident. On climb out after clean and 250 I selected Climb 2 since we were only cleared to 14;000 feet and were climbing at 4800 FPM at such a light weight. Later on; I realized this procedure only applies to our 757 fleet and not the 767. Since I've been flying the 757 much more I guess it was just a habit. I will go back and review my 767 procedural differences more often and do a better job with confirming with the other pilot what I'm doing. Also; [there have been recent changes in procedures]. I've been on the airplane for about 10 years now and procedures have been in a constant state of change as long as I can remember. Hopefully that will all get resolved soon as well.Overall it went well. Approach and ARFF were excellent and helped us out the entire time. Very professional and well done!

Data retrieved from NASA's ASRS site 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.