What was found
DURING COUPLED ILS APPROACH YELLOW ELV LIGHT ON EADI FOLLOWED BY YOKE VIBRATION AND A STRONG RATTLING SOUNDED UNDER CAPT'S FLOORBOARD. PERFORMED OPERATIONAL CHECK OF A/P SYSTEM. ABLE TO DUPLICATE YOKE VIBRATION WHEN SIMULATING APPROACH. SERVO RATTLES UNDER FLOORBOARD (CLUTCH IS RATTLING). CHECKED ALL FLIGHT CONTROLS FOR SMOOTH OPERATION AND TRIM SWITCHES. OPS CHECKS GOOD. DETERMINED PROBLEM TO BE INDUCED WITH A/P ENGAGED. DEFERRED A/P.