What was found
RUDDER SERVO FAILED 4.4 HOURS AFTER INSTALL. RUDDER WENT HARD OVER TO THE LT AND JAMMED IN PLACE. ONCE POWER WAS REMOVED THE PILOTS COULD AT LEAST MOVE THE RUDDER EVEN THOUGHT THE CLUTCH WAS STILL ENGAGED. UPON TEARDOWN FOUND CLUTCH HUB SCREWS HAD BACKED OUT CAUSING CLUTCH ENGAGEMENT WITH NO POWER APPLIED. APPARENT MECHANICAL FAILURE DUE TO HUB RETAINING SCREWS BACKING OUT; MOST LIKELY FROM VIBRATION DURING CLUTCH OPERATION. REPAIRED UNIT AND INCORPORATED SB 7002260-22-A0013.