The likely cause of Alaska Air 737 engine incident was maintenance error
For an airline passenger looking out the window of a jet, it’s alarming to see the metal cover in the midsection of the engine pod flapping open, shredding like thin paper, then ripping off and sending debris backward to ricochet into the wing and fuselage.
That was the troubling view out the windows Monday for passengers aboard an Alaska Airlines Boeing 737. As the San Diego-bound flight lifted off from Seattle-Tacoma International Airport, the covers on both sides of the left engine pod — called a nacelle — came loose.
When the pilots promptly turned back to Seattle, the covers ripped off completely on landing and pieces hit the fuselage.
The jet landed safely and none of the 182 passengers and crew onboard was injured. The passengers were rebooked on another flight.
Dozens of such accidents have happened over the past 30 years, much more often on the Airbus A320 than on the Boeing 737. Though a couple of those incidents turned more serious, none resulted in injuries.
This type of failure is very different from the rarer, but much more dangerous, accidents when an engine fan blade breaks off, causing catastrophic damage to the engine and sending heavy metal shrapnel into the airframe. Those are often caused by undetected long-term metal fatigue in the fan blades.
In contrast, in almost every case of the engine covers’ flapping open and disintegrating, the cause has been traced to a preflight maintenance mechanic error and the subsequent missing of that error during preflight checks.
The Alaska incident was the second such failure on a Boeing 737 in the U.S. this month. On a Southwest Airlines flight from Orlando, Florida, on Aug. 12, the same covers ripped off as the jet landed in St. Louis. Again, no one was injured.
Airbus was forced to modify its A320 design after a series of such incidents.