What was found
LOST USE OF FLAP SYSTEM DUE TO BROKEN SHAFT OR BAD CLUTCH IN POWER DRIVE UNIT. UNIT FAILED DUE TO ACTUATORS BINDING UP BY FREEZING TEMP AT ALTITUDE. UNITS WERE TESTED PER S.I.L. 1125-27-082 PRIOR TO INSTALLING. CHANGED NR 3 RT ACTUATOR, OK FOR 26 HRS, THEN, FAILED AGAIN. TESTED AGAIN UNDER REVISED SIL 1125-27-082. FOUND ACTUATOR PER S.I.L. IN QUESTION. CHANGED 3 EACH ACTUATORS, RETURNED TO SERVICE.