What was found
FLT NR 288 - EWR - TAKEOFF WAS ABORTED AT 60 KNOTS AFTER THE NR 1 ENGINE N1 DROPPED AND THE EGT ROSE TO 950 DEGREES. MAINTENANCE FOUND THE NR 1 ENGINE 14TH STAGE DUCT BLOWN. THE 14TH STAGE DUCT WAS REMOVED AND REPLACED. THE NR 1 ENGINE WAS RUN AT HIGH POWER WITH ALL PARAMETERS AND INDICATIONS CHECKING NORMAL. S/D - THE FAILURE WAS DUE TO HIGH VIBRATORY STRESSES IN THE 14TH STAGE CDP AIR TUBE RESULTING FROM THE 14TH STAGE AIR BLEED TUBE. THE CF6-50 FLEET HAS BEEN MODIFIED BY REMOVING THE 14TH STAGE AIR BLEED TUBE PER GE SERVICE BULLETIN 75-071. (M)