What was found
DURING CRUISE FLIGHT, STRAIGHT AND LEVEL, ACFT SHUTTERED BRIEFLY THEN IN PILOTS HEADSETS HEARD AN AUDIBLE ENGINE OVER-TEMP ALARM. NG AND ENGINE OIL PRESSURE ON THE NR 1 ENGINE WERE AT ZERO AND PILOTS CONDUCTED SINGLE ENG FAILURE PROCEDURE. AFTER DEALING WITH THE ENG FAILURE & WE WERE ESTABLISHED IN SINGLE ENG FLT WE ATTEMPTED AN IN AIR RESTART OF THE NR 1 ENG. WERE UNSUCCESSFUL 3 TIMES TO RESTART DUE TO THERE BEING NO NG INDS. SECURED THE NR 1 ENG AND CONTINUED SINGLE ENG FLT BACK TO ZAMBOANGA. PILOTS DISCUSSED WHAT COULD HAVE FAILED AND CAME UP WITH THE ASSUMPTION THAT THE RADIAL DRIVESHAFT FROM THE COMPRESSOR HAD FAILED AND THE ACCESSORY DRIVE GEARBOX WAS NO LONGER BEING POWERED. WE HAD NOTICED THAT WHEN ATTEMPTING TO RESTART THE ENGINE, TIT WOULD DROP BECAUSE COLD AIR WAS BEING DRAWN IN, SO THE COMPRESSOR WAS ROTATING BUT WE RECEIVED NO NG OR ENGINE OIL INDICATIONS.