AN AIR CARRIER TURBOJET ON ROTATION TO 1400 FT DECLARED AN EMER AND DIVERTED DUE TO A FIRE WARNING IN #1 CAUSED BY A FAILED AFT ENG MOUNT.

Narrative

ACR AIRLINES B727 HAD #1 ENG FIRE LITE AND BELL SHORTLY AFTER ROTATION NO SECONDARIES. COMPLIED WITH PROCS; SHUT DOWN AFFECTED ENG. RETURNED TO ZZZ VIA ILS APCH. SAFE ROLLOUT TO GATE. FLT FROM ZZZ-XXX. SUPPLEMENTAL INFO FROM ACN 503081: DURING TKOF ON RWY 33L AT BOS I BECAME AWARE OF AN ACR Y SAAB 340 SLOWLY MOVING ON TXWY GOLF TOWARD RWY 33L; AT APPROX NINETY KNOTS IT BECAME APPARENT THE SAAB WAS PAST THE HOLD LINE AND ALMOST ONTO RWY. AT THIS POINT ATC ORDERED THE SAAB TO STOP; WHICH HE DID IMMEDIATELY. I DECIDED NOT TO ABORT THE TKOF; FEELING THAT I HAD THE SAAB BEAT THROUGH THE 33L/GOLF INTXN AND THAT DOING SO MAY HAVE CAUSED A COLLISION HAD THE SAAB NOT STOPPED. WE PASSED GOLF INTXN AT 110 KNOTS. V1 WAS 149 KNOTS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A B727-200 AND THE FIRE WARNING WAS NOT A FALSE WARNING. THE RPTR SAID WHEN ON THE GND AND INSPECTING THE ENG IT WAS DISCOVERED THE AFT ENG MOUNT HAD FAILED. THE RPTR SAID THE AFT SECTION OF THE ENG SEPARATED FROM THE STUB WING ALLOWING THE ENG TO SHIFT DOWNWARD AND OUTBOARD 12 TO 16 INCHES. THE RPTR SAID THIS CAUSED PNEUMATIC DUCTING FAILURE GIVING THE FIRE WARNING.