Federal authorities and independent aviation experts are assuring travellers that last week’s emergency aboard Southwest Airlines Flight 812 was an isolated event, which can be addressed with newly ordered inspections of some Boeing 737s.
I have serious doubts about that.
My doubts are strong enough that, for now, I intend to book away from Southwest and onto other carriers wherever possible. This is not a trivial issue for me. I book a lot of flights for myself, my family and my employees, and Southwest is one of my “go-to” airlines. On many routes it offers an unbeatable combination of schedule, convenience and price.
Last month I put my daughter on Southwest for a round trip between Chicago and Fort Lauderdale. I sent my mother on Southwest from Florida to Hartford, Conn. I was planning to book Southwest for myself for a trip next month that will take me from California to Chicago and then to Florida. Now, I won’t.
A five-foot-by-one-foot hole opened in the fuselage just as Flight 812 was reaching cruise altitude on a flight from Phoenix to Sacramento last Friday. The cabin quickly depressurized, giving the crew only 10 to 20 seconds of what experts call “useful consciousness” to don their oxygen masks. The well-trained pilots reacted correctly. After putting on their masks, they quickly brought the plane down from 34,000 feet to below 10,000 feet, where the air has enough oxygen to make masks unnecessary. The pilots then made an emergency landing in Yuma, Ariz.
Nobody was injured. Although a couple of people in the cabin may have fainted or come close to it, passengers generally put on their masks and remained calm.
As soon as word spread about the mishap, every aviator immediately knew what had happened – because it has happened before. Boeing 737s have a history of developing cracks in and near the aircraft skin, especially at the top or “crown” of the fuselage, where Flight 812’s hole appeared. The cracks are usually harmless, and periodic inspections generally catch them. But occasionally, they can cause a section of the skin to rip away.
An Aloha Airlines flight attendant was sucked out of the cabin and died in 1988, when a larger hole opened at the crown of another 737 during a flight in Hawaii. Less than two years ago, a Southwest 737 had to make an emergency landing in West Virginia when another hole opened in its fuselage, also causing the cabin to decompress.
In each instance, the aircraft skin ruptured because of metal fatigue. Every time a commercial jetliner reaches cruise altitude and then returns to earth, it goes through a cycle of pressuring and depressurizing the cabin so passengers and crew can breathe without supplemental oxygen. Each cycle creates stress on the aircraft frame and skin, especially in the crown and around openings such as windows and rivet holes. (Aircraft windows are rounded rather than square to reduce such stresses.) Eventually, the stress causes metal fatigue, which can lead to cracks. If the cracks accumulate in the wrong place, the aircraft can fail catastrophically in flight.
The Boeing 737 is not unique in suffering such stresses, but the way it is used – especially by Southwest – can make it more prone to failure. The 737 is one of the smallest “full-sized” jets, just a step above the larger “regional jets” that have become popular in recent years. It is often used on short-haul flights, so it can make many up-and-down cycles in a day. The 15-year-old aircraft involved in the Flight 812 incident had completed more than 39,000 flight cycles, The New York Times reported – an average of more than seven per day since it went into service. A long-haul jetliner will often average less than one cycle per day, considering the time it is out of service for maintenance.
These short hauls are how Southwest provides the level of cost-efficient service that frequent travellers like me have grown to appreciate. Not too long ago, for example, I needed to fly from Spokane, Wash., to Ontario, Calif. To my surprise, Southwest offered me a convenient flight that would let me do it without changing planes.
My early-morning flight originated in Boise, Idaho. It stopped in Spokane, where I boarded. Then it flew to Seattle, then Oakland, Calif., and on to Ontario, which is a suburb of Los Angeles. From Ontario the flight continued to its final stop in Phoenix. That single journey added five cycles to the aircraft’s history. It arrived in Phoenix early enough in the day to make a similar voyage later in the afternoon or evening, though I do not know how that particular aircraft was scheduled.
The Federal Aviation Administration tightened inspection requirements for 737s after the Aloha Airlines tragedy. Just four months before the 2009 incident in West Virginia, Southwest agreed to pay $7.5 million in fines for failing to properly inspect its aircraft for metal fatigue in 2007.
The FAA’s immediate response to the latest episode was to order a new round of inspections for all 737s that have completed 30,000 takeoff and landing cycles. The inspections are designed to find cracks in out-of-the-way places that would not be visible during routine maintenance checks. The question for travellers is: Are inspections enough?
Most travellers are not aeronautical engineers. We accept on faith that the industry and the government have procedures that are at least reasonably well-targeted to address known problems. In this case, the premise is that if the Flight 812 aircraft had been inspected recently enough – its last inspection was about a year ago – the latest failure could have been prevented.
Does this make sense? To know, we need to know the interval between when a crack first develops and when it can first threaten the integrity of the aircraft. If that span is, say, longer than a year, than thorough annual inspections can do the trick. If it is six months, however, then there is a risk that a plane may be perfect when it is inspected, but still might develop dangerous metal fatigue before it is next due to be checked. In that case, each flight is a game of Russian roulette.
Can detailed inspections be performed often enough to assure that cracks cannot develop to the point that they jeopardize an aircraft? I have not read or heard anything that assures me this is the case.
If not, the answer is not more inspections. It is more preventive maintenance – replacing the components of an aircraft’s skin and frame after a certain number of cycles that is set well below the number that should produce enough metal fatigue to create dangerous cracks.
This will mean taking aircraft out of service more often. Fewer aircraft in service means fewer seats and higher prices. More maintenance means more cost and, again, higher prices. Nobody likes higher prices. But we have to do something that works, because nobody wants aircraft to develop holes at high altitudes, either.
Southwest is not the only airline that flies 737s, and the 737 is not the only aircraft that can suffer failure from metal fatigue. An American Airlines Boeing 757 suffered a failure on a flight last year, which also led to decompression. (Additional inspections were ordered after that incident, as well.) But Southwest’s all-737 fleet, together with its highly efficient, if stressful, use of its aircraft, makes it the U.S. airline that probably is most vulnerable to these failures.
That is why I am booking away from Southwest. I will gladly come back, when someone tells me that the new safety procedures really are well-targeted toward the problem. The government’s demand for more inspections is the easy and obvious answer to the problem, but that does not make it the right one.
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