What was found
(CAN) A/C CAME IN TO THE MAINT HANGER DUE TO HAVING A CHIP LIGHT COME ON IN THE COCKPIT. INSP FROM MAINT NOTICED THAT THERE WAS METAL ON THE CHIP DETECTOR OF ENGINE P-54121. AT THAT TIME THE ENGINE WAS FORWARDED TO THE ENGINE SHOP FOR FURTHER INSP. THE ENGINE WAS DISMANTLED TO FIND THAT THE HIGH SPEED PINION NUT (HSP) PN 893737-3, WAS STARTING TO BACK OFF FROM ITS OVERHAULED TORQUE SPECIFICATIONS. THE HSP WAS OVERHAULED ON THE 22 JULY 05. THE NUT WHEN TORQUED IS SUPPOSED TO HAVE A PIN PN S815N4-0-200 STAKED BESIDE THE NUT TO PREVENT IT FROM BACKING OFF. UPON FURTHER INSPECTION OF THE PIN AREA IT DOES NOT LOOK LIKE THERE WAS EVER A PIN INSTALLED AT THE TIME OF INSP, WITH THE NUT BACKING OFF OF THE HSP THIS COULD HAVE CAUSED A CATASTROPHIC FAILURE OF THE ENGINE IF THE NUT DROPPED INTO THE PLANETARY GEARS. (TC NR 20080124005)