FLC OF A B767 WERE FORCED TO DSND FROM ASSIGNED ALT AFTER L ENG STARTED SURGING AND HAVING COMPRESSOR STALLS DURING CLB TO A HIGHER CRUISE ALT.

Narrative

CLRED INTO BLOCK FL390-FL410; CLBING THROUGH FL400 AND JUST TOPPING A TSTM; THE L ENG BEGAN A SURGE FOLLOWED BY ABOUT 2-3 MINS OF COMPLETE LOSS OF PWR WITH DRAMATIC COMPRESSOR STALLS. I INSTRUCTED FO TO INFORM ATC OF OUR PROB AND THAT WE NEEDED A LOWER ALT IMMEDIATELY. ATC CLRED US TO FL390. I ATTEMPTED TO SLOW THE DSCNT WITH THE HOPE THAT I COULD GET THE ENG BACK BY FL390. THE DSCNT WAS ARRESTED AT FL387 BUT THE AIRSPD BEGAN TO DECAY AS THE ENG SLOWLY BEGAN TO RECOVER PWR. WHEN THE AIRSPD DECAYED TO 220 KIAS AT FL387; I RE-ESTABLISHED THE DSCNT. THE ENG STABILIZED TO NORMAL OP AND WE WERE ABLE TO MAINTAIN FL370. THE ABOVE EVENTS OCCURRED INSIDE THE TSTM WITH LIGHTNING; PRECIP; AND SEVERE TURB. THIS AIRPLANE HAD THE L ENG CHANGED 3 DAYS PRIOR TO OUR FLT AND THEN HAD AN UNSCHEDULED LNDG BECAUSE OF SURGE. ADJUSTMENTS WERE MADE AND OP OF THE PLANE WAS UNEVENTFUL UNTIL OUR EXPERIENCE. I WAS BUSY WITH THE PROB AND I LATER BECAME AWARE THAT MY FO MAY HAVE NOT COMMUNICATED THE SERIOUSNESS OF OUR PROB TO ATC IN A FORCEFUL MANNER.