Narrative:

Aircraft X came in for an 8 block 'C' check. I was assigned a job to stop drill or rout out a crack; on the #1 engine outboard pylon. As I was working in that area; I noticed a hi-lock had a missing collar. This missing collar was on a repair that was done on the pylon. I brought it to my lead's attention. My lead idented the problem and added on my non routine write-up to install missing collar. I then got a hi-lock collar and tried to put it on and noticed the threads on the hi-lock bolt was completely stripped. Working on this particular job already had very limited access. I then decided to replace the stripped hi-lock bolt -- in my opinion would be the right fix. Working with very limited access; I tried several methods of pulling out the stripped hi-lock bolt; but was not successful as the hi-lock bolt was really jammed in there and was being very stubborn. My last option was drilling the hi-lock bolt through the shank; because I did not have much access from drilling through the head of the hi-lock. Once again having limited access; I cautiously tried drilling it out slowly by slowly and tried knocking out the hi-lock; but once again not successful. I continued drilling the shank of the hi-lock bolt. Because of the limited access; my drill but was not perfectly centered with the hi-lock shank and was drilling crooked and caused a snowman type hole. I then informed the lead about the struggle of pulling out the hi-lock bolt and the damage that was done to the pylon. My lead then decided to help me in taking out this stubborn hi-lock and he too wasn't successful. Then my lead decided to get the machine shop tech over. The machine shop technician created a special tool and took off the hi-lock and opens up the damaged hole -- I believe to a 7/16. In this case; the leads and engineering had to notify boeing to see if they could put a freeze plug or a fastener in that hole; or possible repair to the pylon. My supervisor did mention when we came on shift that the 'C' check position was completed; but the airplane was held OTS till they received an engineering acceptance from boeing which was expected at XA30 this morning and comply with the engineering acceptance before releasing the airplane to the airline. Doing the job right the first time and not having a stripped hi-lock which caused the collar to come off.

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Original NASA ASRS Text

Title: A MECHANIC DESCRIBES THE EFFORTS AND FRUSTRATIONS OF REMOVING A HI-LOCK FASTENER WITH A MISSING COLLAR AND STRIPPED THREADS OF A PREVIOUS REPAIR AT THE #1 ENGINE PYLON OF A B757-200.

Narrative: ACFT X CAME IN FOR AN 8 BLOCK 'C' CHK. I WAS ASSIGNED A JOB TO STOP DRILL OR ROUT OUT A CRACK; ON THE #1 ENG OUTBOARD PYLON. AS I WAS WORKING IN THAT AREA; I NOTICED A HI-LOCK HAD A MISSING COLLAR. THIS MISSING COLLAR WAS ON A REPAIR THAT WAS DONE ON THE PYLON. I BROUGHT IT TO MY LEAD'S ATTN. MY LEAD IDENTED THE PROB AND ADDED ON MY NON ROUTINE WRITE-UP TO INSTALL MISSING COLLAR. I THEN GOT A HI-LOCK COLLAR AND TRIED TO PUT IT ON AND NOTICED THE THREADS ON THE HI-LOCK BOLT WAS COMPLETELY STRIPPED. WORKING ON THIS PARTICULAR JOB ALREADY HAD VERY LIMITED ACCESS. I THEN DECIDED TO REPLACE THE STRIPPED HI-LOCK BOLT -- IN MY OPINION WOULD BE THE RIGHT FIX. WORKING WITH VERY LIMITED ACCESS; I TRIED SEVERAL METHODS OF PULLING OUT THE STRIPPED HI-LOCK BOLT; BUT WAS NOT SUCCESSFUL AS THE HI-LOCK BOLT WAS REALLY JAMMED IN THERE AND WAS BEING VERY STUBBORN. MY LAST OPTION WAS DRILLING THE HI-LOCK BOLT THROUGH THE SHANK; BECAUSE I DID NOT HAVE MUCH ACCESS FROM DRILLING THROUGH THE HEAD OF THE HI-LOCK. ONCE AGAIN HAVING LIMITED ACCESS; I CAUTIOUSLY TRIED DRILLING IT OUT SLOWLY BY SLOWLY AND TRIED KNOCKING OUT THE HI-LOCK; BUT ONCE AGAIN NOT SUCCESSFUL. I CONTINUED DRILLING THE SHANK OF THE HI-LOCK BOLT. BECAUSE OF THE LIMITED ACCESS; MY DRILL BUT WAS NOT PERFECTLY CTRED WITH THE HI-LOCK SHANK AND WAS DRILLING CROOKED AND CAUSED A SNOWMAN TYPE HOLE. I THEN INFORMED THE LEAD ABOUT THE STRUGGLE OF PULLING OUT THE HI-LOCK BOLT AND THE DAMAGE THAT WAS DONE TO THE PYLON. MY LEAD THEN DECIDED TO HELP ME IN TAKING OUT THIS STUBBORN HI-LOCK AND HE TOO WASN'T SUCCESSFUL. THEN MY LEAD DECIDED TO GET THE MACHINE SHOP TECH OVER. THE MACHINE SHOP TECHNICIAN CREATED A SPECIAL TOOL AND TOOK OFF THE HI-LOCK AND OPENS UP THE DAMAGED HOLE -- I BELIEVE TO A 7/16. IN THIS CASE; THE LEADS AND ENGINEERING HAD TO NOTIFY BOEING TO SEE IF THEY COULD PUT A FREEZE PLUG OR A FASTENER IN THAT HOLE; OR POSSIBLE REPAIR TO THE PYLON. MY SUPVR DID MENTION WHEN WE CAME ON SHIFT THAT THE 'C' CHK POSITION WAS COMPLETED; BUT THE AIRPLANE WAS HELD OTS TILL THEY RECEIVED AN ENGINEERING ACCEPTANCE FROM BOEING WHICH WAS EXPECTED AT XA30 THIS MORNING AND COMPLY WITH THE ENGINEERING ACCEPTANCE BEFORE RELEASING THE AIRPLANE TO THE AIRLINE. DOING THE JOB RIGHT THE FIRST TIME AND NOT HAVING A STRIPPED HI-LOCK WHICH CAUSED THE COLLAR TO COME OFF.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.