What was found
ON 2 SEPERATE T/O ROLLS AT 60-70 KTS BOTH YD AND MACH TRIM CAME OFF. T.O.S WERE BOTH ABORTED . NOTE: PITOT HEAT INDICATED WORKING AND WAS LT ON FROM TAXI OUT TO T/O ROLL. (EST 20-25 MIN BY 2ND T.O. ATTEMPT) PLANE WAS SITTING IN HEAVY RAIN FOR SEVERAL HRS. PURGED PITOT/STATIC SYSTEMS AS REQUIRED. YAW DAMPER AND MACH TRIM SYSTEM FUNCTIONING NORMAL AT THIS TIME. ALL WORK DONE IAW 750 MM CHAPTERS 22, 30, 34 & 23.