What was found
(CAN) WHEN APU STARTED IT WOULD NOT ACCELERATE PAST 40 PERCENT. INVESTIGATION FOUND A LARGE BREACH OF PLENUM ASSY. NATURE OF FRACTURES APPEARS TO BE FATIGUE RELATED DUE TO VIBRATION. APU REMOVED AND FURTHER INVESTIGATION REVEALED A COMPLETELY DETACHED PIECE BROKEN BRACKET RESTING IN THE COMPRESSOR INLET DUCT. PIECE WAS IDENTIFIED AS A BROKEN FLANGE FROM THE INSIDE OF THE INLET DUCT. INSPECTION OF THE COMPRESSOR ROTOR SHOWED SIGNIFICANT DAMAGE FROM CONTACT WITH THE BRACKET. ELBOW TUBE ASSEMBLY P/N 3846007-1 ATTACHED TOTHE INLET PLENUM WAS ALSO FOUND TO BE LOOSE AND WORN FROM VIBRATION. WHEN THISAPU WAS INSTALLED IT WAS REPORTED TO HAVE A HIGH PITCH WHINE. THE CAUSE WAS NOT DETECTIBLE. IT OPERATED NORMALLY UNTIL