What was found
DURING INITIAL DECENT FROM 350 NR 1 ENGINE BEGAN A THUMPING NOISE ALONG WITH DECAY IN N1 & RISING. EGT N2 WAS MATCHING NR 2 & 3 ENGINES. ENGINE SHUTDOWN, CHECKLIST ACCOMPLISHED, MANUAL SHUT DOWN NR 1 ENGINE FIRE BOTTLE DISCHARGED. REMOVED NR 1 ENGINE LOW PRESSURE BLEED CHECK VALVE IAW AMM 36-11-03-2. FOUND STOP TUBE INSIDE THE CHECK VALVE SHEARED & MISSING. NR 1 ENGINE STALL INSPECTION & CHECK CARRIED OUT IAW AMM 72-00-00-6-1. LOW PRESSURE CHECK VALVE R & R IAW AMM 36-11-03-2. NR 1 ENGINE IDLE RUN CARRIED OUT IAW JRH. ALL PARAMETERS & INDICATION NORMAL. ACFT OK FOR SERVICE.