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A line mechanic reports he misread a depth dial indicator measurement of a B757-200 external fuselage lightning strike damage that allowed the aircraft to continue in service for another 50 hours or 25 cycles. A later reinspection of the damaged area determined the depth to be twice what he originally noted.
| Attributes | |
| ACN | 843667 |
| Time | |
| Date | 200907 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Parked |
| Component | |
| Aircraft Component | Longeron/Stringer |
| Person 1 | |
| Function | Technician |
| Qualification | Maintenance Airframe Maintenance Powerplant |
| Experience | Maintenance Lead Technician 10 Maintenance Technician 11 |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Deviation - Procedural Maintenance Deviation - Procedural FAR Deviation - Procedural Published Material / Policy |
Narrative:
A B757-200 aircraft arrived in ZZZ in july 2009; with a pilot report of a lightning strike. Numerous strikes were detected along the left side of the fuselage and one strike found on the upper fuselage. Time limited repairs were accomplished in several locations. The damage at sta 822 S-4L was removed and needed to be measured for depth in the skin. I used a depth dial indicator for this measurement. I misread the graduations on the dial indicator and recorded a depth of .024. This amount of damage in the skin allowed the aircraft to continue on for 50 hours or 25 cycles. The aircraft was released for flight. Upon re inspection of the damage; the depth of the damage was measured to be .050. This is twice the depth of what I measured. I looked at the dial indicator that I used and discovered my mistake. I counted the graduation on the scale incorrectly and came up with the wrong measurement.
Original NASA ASRS Text
Title: A Line Mechanic reports he misread a Depth Dial Indicator measurement of a B757-200 external fuselage lightning strike damage that allowed the aircraft to continue in service for another 50 hours or 25 cycles. A later reinspection of the damaged area determined the depth to be twice what he originally noted.
Narrative: A B757-200 aircraft arrived in ZZZ in July 2009; with a Pilot report of a lightning strike. Numerous strikes were detected along the left side of the fuselage and one strike found on the upper fuselage. Time Limited repairs were accomplished in several locations. The damage at STA 822 S-4L was removed and needed to be measured for depth in the skin. I used a Depth Dial Indicator for this measurement. I misread the graduations on the Dial Indicator and recorded a depth of .024. This amount of damage in the skin allowed the aircraft to continue on for 50 hours or 25 cycles. The aircraft was released for flight. Upon re inspection of the damage; the depth of the damage was measured to be .050. This is twice the depth of what I measured. I looked at the Dial Indicator that I used and discovered my mistake. I counted the graduation on the scale incorrectly and came up with the wrong measurement.
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.