Airline Safety
8:01 am
Tue April 5, 2011

Boeing helps with Southwest Airlines investigation

Boeing says it’s providing technical assistance to federal aviation regulators and to Southwest Airlines in the wake of Friday’s mid-flight incident where a hole appeared in the skin of a 737 airliner at 34,000 feet.

The Seattle Times reports that the sudden rupture has experts concerned because the stress-related failure of the aircraft’s aluminum skin occurred mid-fuselage. That's a place that was not previously thought to be vulnerable to that kind of damage. 

The Seattle Times quotes John Hart-Smith, a world-renowned expert on metal-aircraft structures and a retired high-level Boeing engineer, as saying ...

It's a much thicker skin there. Typically, that area has never been susceptible to cracking at the lap splices.

The lap splices are the areas where sections of the aircraft's skin overlap and are riveted together.

The skin is vulnerable to tiny cracks over time from the repeated stress of taking off, flying at high altitude, then landing. Airline maintenance inspections routinely look for that kind of wear-and-tear on certain parts of the plane.  

Southwest, like most domestic airlines, flies a lot of short routes, so its planes often take off and land six or more times a day. 

The latest incident on Southwest flight 812 is prompting the Federal Aviation Authority to issue an emergency directive. It requires about 175 older 737-300, 400 and -500 models to be inspected with a type of electromagnetic process that detects stress cracks invisible to the eye.

Most of these aircraft belong to Southwest. The airline has been doing those inspections and has turned up three other 737s with similar weaknesses.

Boeing officials say they’re preparing a service bulletin that will recommend inspections of certain 737 models that will focus on the lap-joint area that failed on the Southwest flight last week.