When Alaska Airlines flight 1282 took off around 5 PM Friday, Jan. 5 from Portland, Oregon, few if any of the 171 passengers suspected that anything unusual was going to happen. But at 5:11 PM, as the Boeing 737 Max 9 was climbing through 16,000 feet, passengers heard a loud bang followed by a roaring wind noise that made conversation impossible. Where a normal porthole window had once been, a gaping two-by-four-foot hole had appeared next to a row of seats on the left side of the plane. One passenger, Kelly Bartlett, didn't realize what had happened until a teenage boy moved into an empty seat next to her. He was sitting in the row next to the hole, two empty seats away from the window, and the blast sucked the shirt off his back. If he hadn't been wearing his seatbelt, he might have gone with it.
Oxygen masks deployed all over the plane, and the passengers remained calm amid the chaotic noise. The pilot immediately returned to Portland and landed the plane safely. No one other than the boy next to the hole was injured.
The Boeing 737 Max 9 can be configured for various numbers of seats, and for more than 200, an emergency exit is required in the location where the hole appeared. But for smaller capacities, the emergency exit is replaced by a panel, basically a plug the shape of the exit door, that blocks the exit opening. From inside the plane, the window and trim make this plug almost invisible. But all that was holding it against the differential pressure of over a ton as the plane rose through 16,000 feet were four bolts, at least if the plug had been installed correctly. This particular Max 9 was delivered to Alaska Airlines only last October, so the problem may have existed since it was built.
A Portland high-school teacher found the door intact in his back yard, so investigators are looking at it closely to determine the cause of the failure.
In the meantime, the U. S. Federal Aviation Administration (FAA) has grounded all Boeing 737 Max 9 planes, which affects some 171 aircraft. It has ordered inspections of the bolts and other structures around the door plugs, and United Airlines has already found that some bolts on its door plugs are loose.
Only last week, we described in this space how all passengers on a commercial flight involved in a runway collision in Japan survived with only minor injuries, and we can fortunately say the same about this accident in Portland. But things could have been much worse. In similar incidents involving sudden holes in fuselages, passengers or flight attendants have been sucked out bodily. If the boy sitting next to the hole hadn't been wearing his seatbelt, that probably would have been his fate. And if the plug had waited to fail at a higher altitude, the pressure differential would have been greater, possibly tearing a seat off its mounts.
Although we can rejoice that nobody was seriously injured, the big question now is why the plug blew out. The fact that at least one other plane has been found with loose bolts holding the plug says that this may not have been an isolated incident. That is why the FAA has wisely grounded the Max 9s until a thorough investigation shows exactly what the problem was.
We can only speculate at this point, but already some things are fairly clear. The fact that the plane suffering the accident was so new points to a possible manufacturing problem. Nuts on airframes must be torqued to a specific tension, because the proper amount of torque represents a compromise between not enough tension on the bolt, which might leave it subject to vibration loosening or fatigue in some cases, and too much tension, which could lead to bolt failure. Many bolts on aircraft have locking cables, cotter pins, or other means by which the nut on the bolt is prevented from turning. It's not clear whether the four bolts that hold the door plug in place had such provisions, but even locking devices can fail, or be improperly installed.
Another 737 Max series, the Max 8, was the subject of an extensive and expensive investigation involving defective software that intentionally crashed the plane when it received faulty data from attitude sensors. This problem cost Boeing billions of dollars and lost prestige, and the last thing the company needs right now is another expensive and embarrassing safety problem.
In a statement to employees that was also released to the public, Boeing CEO Dave Calhoun promised "100% and complete transparency every step of the way" during the investigation. He can hardly promise less, because Boeing's reputation is on the line with every accident that points to a manufacturing cause.
As airlines which own 737 Max 9s wait impatiently to begin using their millions of dollars of investment again, both the FAA and Boeing have big incentives to figure out why the plug blew out and how to make sure it doesn't happen again. The recovery of the intact door will be very helpful in the investigation, and I expect we will know something definite within 60 to 90 days.
In the meantime, air flight remains a safe mode of travel for the vast majority of passengers. The incredible number of things that all have to work flawlessly for a typical flight to be completed goes completely unnoticed by most passengers, but it is the product of the efforts of thousands of engineers, technicians, service people, pilots, crew members, air traffic controllers, and others who do their jobs without public recognition.
We are fortunate that the last two attention-grabbing commercial aircraft accidents have resulted in relatively few casualties. But grounding the Max 9s was the right thing to do, and everyone looks forward to the time when we can know what happened, why it happened, and how to keep it from happening again.
Sources: I referred to the FAA website at https://www.faa.gov/newsroom/updates-grounding-boeing-737-max-9-aircraft and the following news reports: https://abcnews.go.com/US/alaska-airlines-emergency-fittings-top-door-plug-fractured/story?id=106218951, https://www.npr.org/2024/01/08/1223517098/door-plug-boeing-737-max-portland-ntsb-faa. and https://abc7ny.com/alaska-airlines-flight-emergency-boeing-door-plug/14298712/.
No comments:
Post a Comment