Narrative:

On takeoff/climb from ZZZ1 to ZZZ2, we got an ECAM message for a faulty bleed valve on our #1 (left) engine. We followed air carrier procedures and closed the bleed valve switch. This may or may not have an effect on the following situation. Everything continued normally at our cruise altitude of FL390 for about 1 1/2 hours. Over abc while in light turbulence we noticed a very noticeable vibration and the #1 (left) engine rolled back to 40% N1 and was unresponsive to any thrust lever movement. We started to lose airspeed, declared an emergency and started a descent. At that time the #1 engine spiked toward yellow/red line, and the thrust lever was moved to idle. We leveled off at 11000 ft and found the #1 engine was running properly and continued on to ZZZ3 and made an uneventful landing.

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Original NASA ASRS Text

Title: AN A320 EXPERIENCED A PWR LOSS AT FL390. CONDUCTED AN EMER DSCNT TO 11000 FT WHERE THE ENG OPERATED NORMALLY. THE CREW LANDED AT THE NEAREST SUITABLE ARPT.

Narrative: ON TKOF/CLB FROM ZZZ1 TO ZZZ2, WE GOT AN ECAM MESSAGE FOR A FAULTY BLEED VALVE ON OUR #1 (L) ENG. WE FOLLOWED ACR PROCS AND CLOSED THE BLEED VALVE SWITCH. THIS MAY OR MAY NOT HAVE AN EFFECT ON THE FOLLOWING SIT. EVERYTHING CONTINUED NORMALLY AT OUR CRUISE ALT OF FL390 FOR ABOUT 1 1/2 HRS. OVER ABC WHILE IN LIGHT TURB WE NOTICED A VERY NOTICEABLE VIBRATION AND THE #1 (L) ENG ROLLED BACK TO 40% N1 AND WAS UNRESPONSIVE TO ANY THRUST LEVER MOVEMENT. WE STARTED TO LOSE AIRSPD, DECLARED AN EMER AND STARTED A DSCNT. AT THAT TIME THE #1 ENG SPIKED TOWARD YELLOW/RED LINE, AND THE THRUST LEVER WAS MOVED TO IDLE. WE LEVELED OFF AT 11000 FT AND FOUND THE #1 ENG WAS RUNNING PROPERLY AND CONTINUED ON TO ZZZ3 AND MADE AN UNEVENTFUL LNDG.

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.