What was found
AT TOP OF DESCENT, THE NR 4 ENGINE EXPERIENCED A MILD COMPRESSOR STALL. AS EGT STARTED TO CLIMB TO APPROXIMATELY 850 DEGREES, CREW FOLLOWED COM PROCEDURE, SHUT DOWN THE ENGINE AND ACCOMPLISHED A SUCCESSFUL RESTART AT FL240. FLIGHT CONTINUED TO NRT WITHOUT FURTHER INCIDENT. BORESCOPE INSPECTION OF 8TH, 9TH AND 15 STAGES OF HPC REVEALED NO DISCREPANCIES. MAINTENANCE CHANGED THE PRBC, CONVERTER VALVE, AND PS4 RESTRICTOR.