What was found
NR 1 IN FLIGHT SHUTDOWN OF RT PACK DUE TO EXCESSIVE VIB AND NOISE. INSPECTED NOSE AND PAC SECTION OF ACFT. SUSPECT PACK WAS RUNNING WHEN NR 4 ENG WAS ALSO MALFUNCTIONING, SYS LEAK AND OP CHECKS GOOD. TOP OF DESCENT NR 1 ENG WENT BELOW MIN FLIGHT IDLE TO 32 PERCENT N1. REPLACED 51-68 OLEO SWITCH, SYS OP CHECK GOOD ON ENGINE RUN BY MAINTENANCE TEAM. TOP OF DESCENT NR 4 ENG WENT BELOW MIN FLIGHT IDLE TO 30 PERCENT N1. REPLACED R2-44 RIGHT GROUND RELAY AND 51-69 NOSE OLEO SWITCH, SYS OP CHECK GOOD ON ENGINE RUN BY MAINTENANCE TEAM.