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What: American Airlines Boeing 757-200 from Miami,FL to Boston,MA
Where: Miami
When: Oct 26th 2010
Who: 154 passengers and 6 crew
Why: A half hour after takeoff, the plane developed rapid decompression at 31,000 feet requiring oxygen masks, an emergency descent and a return to Miami.

Maintenance found a one by two foot hole in the hull.

George’s Point of View

Maintenance, Maintenance, Maintenance!

Even with AD Directives issued, this was still missed. Was there telltale evidence prior to this event that could have prevented endangering 154 passengers and six crew?

The hole in the hull is not unprecedented. Sixteen months prior to flight AA-1640, Southwest Airlines (SWA) flight 2294, (another Boeing suffering a hole in the hull in July 13, 2009), the FAA has already issued Airworthiness Directive 2010-01-09 mandating inspection requirements. At that time, they ascribed the hull failure to a design fault: Fuselage skin failure due to preexisting fatigue at a chemically milled step.

It’s an easy enough thing to visualize-picture slightly squeezing an empty cola can, then blowing into it; and repeating the process, over and over. In a soda can, it would not take the 20 years this plane has been flying for the stressed areas to develop a crease, and eventually crack.

Not that a soda can is expected to sustain the significant pressures at 10,000+ feet, nor does it have the design flaw of chemical milling, nor is its skin made of single and double bonded layers. If it were, one could theoretically presume and anticipate metal fatigue to occur at the weakest location–the edges of where the metal is double-bonded.

In the Southwest Airlines event, it was observed that the progression of metal fatigue tends to be higher at the borders between chemically milled and non-chemically milled bays.

The inspection requirements in SB 737-53A1301 require inspections to detect cracks in the vulnerable areas (the chem-mill step) to avoid sudden fracture and failure of the fuselage skin panels.

Did this plane undergo “repetitive external non-destructive inspections to detect cracks in the fuselage skin“?

Carriers out there, when there are directives which indicate potential problems, pay attention!

If not for the stellar performance of this flight crew, this plane would have been a statistic.

Thank you, John D King for sending the links.