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A mechanic was unsatisfied with the position of a right forward cone bolt he installed into a #2 engine vibration isolator; during an engine installation on a B737-500. He later discovered that any cocking (twisting) would cause the cone bolt eye to hit the attach mount.
| Attributes | |
| ACN | 842744 |
| Time | |
| Date | 200906 |
| Local Time Of Day | 0001-0600 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B737-500 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Parked |
| Component | |
| Aircraft Component | Powerplant Mounting |
| Person 1 | |
| Function | Technician |
| Qualification | Maintenance Airframe Maintenance Powerplant |
| Experience | Maintenance Technician 14 |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Deviation - Procedural Maintenance Deviation - Procedural Published Material / Policy |
Narrative:
June 2009; our crew started installing the #2 engine on a B737-500 aircraft. I was working the right hand forward position. While installing the engine up to the cone bolt into vibration isolator mount; everything normal until torquing the right forward cone bolt nut reached correct torque and attempted to remove the alignment fork for the cone bolt and it was stuck. Eventually removed fork and wondered why it was so hard to remove; found that the cone bolt had cocked. So I was concerned and backed the attach nut off the cone bolt until I could realign the cone bolt and reinstall the fork and retorque. After retorque found that removal of the fork was easier but slightly stuck. Then looked at the alignment of the cone bolt to engine mount was better but still slightly cocked. So I thought to myself; well I got the torque with the alignment tool installed and inspection witnessed that I would be alright. So moved on with the rest of the installation not thinking much else about it; until july 2009; when I had brought up the issue I had with the mount and if they had ever encountered it before; they said no; so I thought that there might be a problem.going back to the amm again to the torquing procedure and realized that the cocking that was mentioned in the amm; was a twisting motion of the cone bolt and not an angle cocking of the cone bolt. So I went over to our engine shop and looked at the cone bolt of a spare engine and realized that any small amount of cocking (twisting) of the cone bolt would cause the cone bolt eye area to hit the attach mount; so being concerned I alerted my supervisor about the possible problem. I did not have much experience doing engine changes. Then he and I went directly to the shift supervisor to alert him of the situation.
Original NASA ASRS Text
Title: A Mechanic was unsatisfied with the position of a right forward cone bolt he installed into a #2 engine vibration isolator; during an engine installation on a B737-500. He later discovered that any cocking (twisting) would cause the cone bolt eye to hit the attach mount.
Narrative: June 2009; our crew started installing the #2 engine on a B737-500 aircraft. I was working the right hand forward position. While installing the engine up to the cone bolt into vibration isolator mount; everything normal until torquing the right forward cone bolt nut reached correct torque and attempted to remove the alignment fork for the cone bolt and it was stuck. Eventually removed fork and wondered why it was so hard to remove; found that the cone bolt had cocked. So I was concerned and backed the attach nut off the cone bolt until I could realign the cone bolt and reinstall the fork and retorque. After retorque found that removal of the fork was easier but slightly stuck. Then looked at the alignment of the cone bolt to engine mount was better but still slightly cocked. So I thought to myself; well I got the torque with the alignment tool installed and Inspection witnessed that I would be alright. So moved on with the rest of the installation not thinking much else about it; until July 2009; when I had brought up the issue I had with the mount and if they had ever encountered it before; they said no; so I thought that there might be a problem.Going back to the AMM again to the torquing procedure and realized that the cocking that was mentioned in the AMM; was a twisting motion of the cone bolt and not an angle cocking of the cone bolt. So I went over to our engine shop and looked at the cone bolt of a spare engine and realized that any small amount of cocking (twisting) of the cone bolt would cause the cone bolt eye area to hit the attach mount; so being concerned I alerted my Supervisor about the possible problem. I did not have much experience doing engine changes. Then he and I went directly to the Shift Supervisor to alert him of the situation.
Data retrieved from NASA's ASRS site as of April 2012 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.