What was found
RIGHT ENGINE EXPERIENCED 2 INCIDENTS OF SURGE AS EVIDENCED BY POPPING NOISE AND RPM ROLLBACK FOLLOWED BY FULL RECOVERY. PARAMETERS ARE NORMAL. SURGE WAS NOT COMMENSURATE WITH THROTTLE MOVEMENT. ALL FIM TROUBLESHOOTING, INCLUDING EXTENSIVE BOROSCOPE INSPECTION (BSI), REVEALED NO CONDITION TO ACCOUNT FOR THE SURGE. NO FAULT FOUND. SUSPECT WAKE TURBULENCE ENCOUNTER. MM BLENDED SOME VERY MINOR HPC BLADE DAMAGE FOUND DURING BSI. THIS DAMAGE WAS NOT SUFFICIENT TO CAUSE ENGINE SURGE AND COULD HAVE CONTINUED IN SERVICE WITHOUT BLENDING. THE PROBLEM DID NOT REOCCUR.