GN 012.6 - Gouge, Scratch, Dent & Stain in Pressurised Aircraft Aluminium Alloy Fuselage
- Details
- Category: Use & In-Service Inspection
| APEK - AICIP GUIDANCE NOTE |
SIGNS OR INDICATIONS IN IN-SERVICE GOUGE, SCRATCH, DENT & STAIN IN PRESSURISED AIRCRAFT ALUMINIUM ALLOY FUSELAGE |
APEK GN 012.6 Rev 1 |
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1 Figure |
 
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2 PE involved |
Boeing 747-200 passenger aircraft at P = 60 kPa; T = -50 to 30°C |
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3 Sign(s) |
Initially – axial gouges in hull with probable shallow flat (dent). |
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4 Location of Signs |
In bottom and rear outside of pressure hull (fuselage) at x above. |
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5 When & Where occurred |
In 3 major stages: Initial damage:- “tail strike” on right landing or at rapid rise take-off, in 1982 when aircraft 2 years old. Temporary repair with patch added. Final explosion May 2002 on reaching nearly 35000 ft over South China Sea. Age: 23 years. |
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6 Detection & Investigation |
Initially – VT. Final accident investigation showed brown stains to be nicotine:- based from early cigarette smoke in cabin leaking through crack in fuselage and patch. |
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7 Failure mode(s) (damage mechanisms) |
Fatigue with about 10,000 pressure cycles. Pressure hull sheets mechanically gouged, scratched and dented along the outside and slight deformation; fatigue crack growth; and finally ductile overload rupture. |
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8 Most probable causes |
“Tail-strike” and damage temporary repaired. Fatigue crack from longitudinal gouges reached critical size and between 3 circular ribs?; after nearly 15,000 pressure cycles. |
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9 Outcome |
Aircraft burst into 4 main parts. All 225 people killed. Fines, compensation, and reputation, financial loss. Improved knowledge, maintenance and inspection.
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10 Most Possible Prevention |
Improved landing/take-off; proper and timely repairs (follow rules and check done); take heed of unusual signs, (stain or leakage); good communication and management. |
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11 Comment |
This disastrous failure shows the need to: .1 reassess “temporary repairs” (not possible to see condition of pressure hull sheets under patches). .2 consider properly all signs – brown stain was possibly noted early and well before final explosion but not followed up. If noted, contamination from external service may have been assumed. .3 replace temporary repairs before becoming unsafe .4 not ignore unusual signs – may be a warning – investigate if consequences are very high and find most probable cause. .5 Note that pressure vessels with axial gouges or cracks in dents are highly hazardous as pressure opens up the gouge any fatigue will extend crack as above. A derailed LPG rail tank car with similar defects exploded in USA in 1970s killing 12 people, and causing multi-million $ damage. This was due to morning sun heating LPG, raising its pressure and so reverse the dent and rupture the shell. See Case A15. .6 Consider knock-on effects - an additional outcome in 2009 was $10 million fine for a US airline for not inspecting on time. |
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12 References |
Air Crash Investigation. Channel 7. Sydney 23/12/2009 http://www.youtube.com/watch?v=DAQO2JBXnwg&list=PLtKoPr63_39us6R-9SceIDJ4FOxAIwuiS |
