Boeing Never Expected Southwest Airlines 737 Skin Rupture!

[Guest fountainhall]

Here’s one to think about. Following the rupture in the fuselage of one of Southwest Airlines older 737s and the grounding of a portion of its fleet, the New York Times has analysed the average ages of fleets in the US.

 

Did you know, for example, that the core of American Airlines fleet, its MD80s, have been in the air for 21.04 years, or its Airbus A300s for 22? If that sounds long, how about Delta Airlines 32 DC9s still in service? Once the workhorse of several fleets in the US, would you believe they are on average 38.61 years old? Compare that to their A330s, mere tots at 5.97. US Airways Boeing 767s are 22, as are their 737s, three years older than those in Southwest’s fleet. United Airlines 757s are 19.22 and their Boeing 747s 16.07

 

http://intransit.blogs.nytimes.com/2011/04/06/how-old-is-your-plane/

 

All six 5-star airlines - according to the Skytrax polls - are in Asia. Of these, Cathay Pacific’s fleet averages 11.1 years, with its 747s being 15.2 years but 777s just 6.5 years. Singapore Airlines’ fleet averages 6.4 years, Asiana’s 8.2 years, whilst Qatar, a much younger airline, is just 4.6 years.

 

Yet, back to the Southwest 737 incident. An article in the Business Section of yesterday’s Bangkok Post (7th) headed “Boeing Cracks Came Too Soon” quotes a Boeing executive as saying the company never expected failures in the riveted skin joints running along the top of the 737-300, 737-400 and 737-500 models until these aircraft were much older. ‘Much older’ was defined as around 60,000 take-off and landing cycles. The Southwest 737-300 had completed only about 39,000 cycles.

 

Well, now they know! Apparently, whilst much of the fleet was grounded, similar cracks were found in another 5 of Southwest’s 737s. Long haul aircraft like the 747, 777, Airbus A330, A340 and A380 go through far fewer cycles and so should not be subject to the same sort of skin failures. Even though much of an older aircraft is replaced during its regular maintenance schedule so that it becomes almost new, I’m not sure I’ll want to fly on one of those Delta DC9s!

[Guest]

I never expected Boeing to admit they expected this.

Of course, if they expected failure at only 50% more cycles, then this would correspond to only small error in the loading they used for the fatigue analysis -maybe 10% give or take a few percent.

 

These 737s are frequently used by low cost airlines with rapid turnarounds of the planes & therefore many take off & land cycles. Perhaps their depreciation costs will now have an unwelcome increase.

[Guest GaySacGuy]

I think that the probable reason that Southwest had the problem first is like z909 said..the number of turnarounds. SW flies a lot of short hauls, and keeps their fleet in the air. But every take off and landing is another pressurization of the aircraft, and this has to add stress..so the early failure.

[Guest fountainhall]

As I understand it, the maintenance schedules for short-haul aircraft should account for these constant and frequent pressure changes by means of a complete replacement of the outer skin over time. I thought Boeing and the airlines would have been ultra careful about this following the Aloha Airlines incident in 1988 when a whole chunk of the forward passenger section of the aircraft just exploded away. The ostensible cause was metal fatigue due to corrosion from the salt sea air. Yet that particular aircraft had flown an extraordinary 89,000 cycles in its 19 year history, at that time the second highest of any aircraft in the world and well beyond the 75,000 it was then designed to sustain. Seems experts sometimes just do not connect the dots.

[Jason1988]

Southwest Airlines has been in trouble before for not following government mandated maintenance schedules for their planes. Just another example why low cost airlines are not always the best choice when flying in the USA.