What was found
DURING DESCENT THE AIRCRAFT HAD A PRONOUNCED VIBRATION IN THE CONTROL YOKE, FLAPS AT 22 DEGREES, SPEED BETWEEN 140 AND 180, NO CHANGE, GEARS DOWN, NO CHANGE. ONCE FLAPS SET TO 45 DEGREES VIBRATION WENT AWAY. MAINTENANCE INSPECTED AND PERFORMED A FLAP LATERAL BACKLASH CHECK, PERFORMED A GVI OF THE ELEVATORS, AILERONS, RUDDER AND FLAPS. COULD NOT FIND A DEFINITIVE FAULT. RELEASED AIRCRAFT FOR A TEST FLIGHT. FLEW A TEST FLIGHT NO DEFECTS FOUND AND AIRCRAFT WAS RELEASED FROM TEST FLIGHT.