What was found
DURING TAKE OFF LEFT ENGINE N3 WENT TO OVER SPEED AND SHOWED DIFFERENCE BETWEEN ENGINE PARAMETERS, LH ENGINE HIGHER THAN THE RT, THE ENGINE DIDN’T SHUT DOWN, THE CREW PROCEEDED TO RETURN TO EDR. CORRECTIVE ACTION: PERFORMED BITE TO BVCU, FOUND ALTITUDE SWITCH FAIL CODE; THE ALTITUDE SWITCH S1042 WAS REPLACED IAW AMM 75-32-07 ADDITIONALLY, SWAPPED THE FUEL FLOW GOVERNOR IAW AMM 76-11-000 PAGE 532 ALSO PERFORMED RIGGING TO FUEL FLOW SYSTEM IAW AMM 71-11-00, LH ENGINE RUN UP PERFORMED IAW AMM 71-00-00, WITH SATISFACTORY RESULTS.