What was found
CRACK IDENTIFIED IN THE 9-12 DRUM (LLP). ENGINE SN V18736 WAS INDUCTED FOR INVESTIGATION OF HIGH N2 VIBRATION AND PERFORMANCE LOSS. THIS IS A FIRST RUN ENGINE WITH NO PRIOR SHOP VISITS FROM NEW. DURING THE DISASSEMBLY AND INVESTIGATION OF THE HPC THE CHCEC HAS DISCOVERED A CRACK IN THE 9-12 DRUM AT THE MATING FLANGE TO THE HPC REAR SHAFT. THE CRACK IS RUNNING APPX 50% OF THE CIRCUMFERENCE OF THE DRUM AND CHCEC BELIEVES THIS IS THE CAUSE OF THE HIGH N2 VIBRATION.