What was found
WHILE PERFORMING POST MAINTENANCE ENGINE RUN FOR AN UNRELATED ACTION, THE LEFT ENGINE FAILED TO RESPOND TO THROTTLE MOVEMENT. UPON FURTHER INVESTIGATION THE LEFT ENGINE TORSION TUBE ASSY (P/N MY20571-53810) WAS FOUND BROKEN APPART INSIDE THE ENGINE PYLON BETWEEN FUSELAGE STATION FR31 AND FR32. THE BREAK WAS LOCATED AT THE INBOARD SECTION OF THE TORSION TUBE IDENTIFIED AS A "SEAL" AS SHOWN IN FALCON 20 IPC CHAP, 76-10-20, PAGE 50-0, ITEM 50, P/N UAE651. INTEGRATED INTO THIS PART IS A METAL "UNIVERSAL-JOINT TYPE CONFIGURATION WHICH HAD CRACKED COMPLETELY THROUGH.