Boeing 737-900 MAX loses its cool
Well, 2024 sure has arrived with a bang. It’s a little too soon to draw firm conclusions about the MAX 9 incident, but let’s see what we’ve got so far.
On the 5th of January, a Boeing 737-900 MAX registered in the US as N704AL was operating Alaska Airlines flight 1282, a scheduled passenger flight from Portland, Oregon in the US to Ontario International Airport in California. There were 171 on board.
Shortly after departure, after climbing through 14,000 feet, the cabin experienced a rapid decompression. Flightradar24 shows the maximum altitude as 16,325 feet above mean sea level.
The flight crew quickly reacted, entering a descent and declaring an emergency. The flight returned to Portland safely. The aircraft was airborne for 20 minutes.
You can hear the ATC audio on this video by REAL ATC on YouTube:
The Boeing was just a few months old, with its first flight on the 15th October 2023 and delivery to Alaskan Airlines on the 31st.
It had operated 134 cycles (a cycle is a single take-off and landing) by the end of the year, thus there should not yet be any risk of fatigue.
Passengers heard a loud bang as a door-sized hole suddenly appeared in the middle of the cabin. The oxygen masks dropped.
This video from TikTok was taken by a passenger seated a few rows back:
@strawberr.vy Girls’ trip turned into emergency landing trip… alaska alaskaair ♬ original sound – vy 🍓
The cabin crew, still in their jumpseats, were very unsure as to what was happening as they had difficulty seeing into the cabin. At the same time, the flight crew were taken by surprise by the cockpit door opening. This apparently automatically happens on a rapid decompression; however, this was not documented in the flight crew procedures.
Thankfully, the two passenger seats next to the breach were not occupied. Passengers were still seated with seatbelts on and the fuselage part — now known to be a door plug — did not strike any other part of the aircraft as it detached.
The 63-pound door plug (28.5 kilos) was in place to seal an unused emergency exit. The mid-cabin exits in the 737-900 are optional and for most operators, they are deactivated. If deactivated, the exit is blocked with a door plug, a door-sized piece of fuselage with a window. Inside the cabin is a standard interior sidewall.
The NTSB made press statements every day from Portland for the first three days after the incident.
On the first briefing, they asked for help in retrieving the door plug.
School teacher Bob Sauer saw the news but didn’t realise that he was in the drop zone until late on Sunday evening. OregonLive reported on the find:
It was dark and raining out. As he stepped around the corner of his house, he shined his light along a bank of cedar trees that he and his children had planted about 20 years ago to separate his property from his neighbor.
Suddenly, he noticed something white gleaming in the beam of his flashlight. He stepped a little closer, and there was the “missing piece from the airplane,” he said.
Sauer was interviewed during the beginning of his Monday morning astronomy class. Reporters were treated to an unexpected physics discussion as he explained how the door plug slowed down as it fell through the trees.
He said that the 50-foot cedar trees in his yard had acted on the same scientific principle as an airbag, disrupting the door plug’s fall — in an act known in physics as impulse.
“Impulse is what you do to change the momentum of something,” Mr. Sauer said. “You can do it with a big force over a short time, or a smaller force over a longer time.”
He said an even more relevant lesson, beyond the sheer physics of the drop, was that amazing things can happen.
Meanwhile, Boeing’s CEO released a statement saying that Boeing must acknowledge their mistake and did not argue the grounding of MAX 9 aircraft in the US. The Guardian published details of the internal meeting at Boeing.
“We’re going to approach this – number one – acknowledging our mistake,” Dave Calhoun told Boeing employees at an all-hands meeting at its factory in Renton, Washington, where 737s are assembled, on Tuesday. “We’re going to approach it with 100% and complete transparency every step of the way.”
The US government’s Federal Aviation Administration (FAA) stated that they were conducting a separate investigation, saying, “This incident should have never happened and it cannot happen again.” They published the letter notifying Boeing of the investigation on Wednesday.
The above-described circumstances indicate that Boeing may have failed to ensure its completed products conformed to its approved design and were in a condition for safe operation in accordance with quality system inspection and test procedures.
This is a striking contrast to the Boeing and FAA response after the first crash of the MAX 8, Lion Air flight 610.
Jon Ostrower and Will Guisbond, writing for The Air Current, heard from unnamed insiders that the aircraft in question had pressurisation alerts the day before.
The first intermittent warning light appeared during taxi-in following a previous flight, which prompted the airline to remove the aircraft from extended range operations (ETOPS)per maintenance rules. The light appeared again later the same day in flight, the people said.
If you’ll allow me a bit of gallows humour in an incident with a happy ending for everyone but the aircraft and no injuries, I was sent this image which made me laugh out loud.
The focus at the moment seems to be on four stop bolts which prevent the door plug from moving upwards and disengaging the 12 stop pads. All 12 stops were disengaged; however, the four bolts have not been recovered. The NTSB stated in the Tuesday briefing: “We have not yet determined if they existed.”
Meanwhile, in the United States, all 171 Boeing MAX 9 aircraft (operated by Alaska Airlines and United Airlines) are grounded until they can be inspected, a process which takes about 8 hours per aircraft. There are another forty-four MAX 9 jets in service outside of the US. Airlines in Brazil, Mexico, Indonesia and Panama have suspended operations of the affected MAX 9 aircraft pending an inspection. Chinese airlines have not accepted any Boeing MAX aircraft since they initially grounded the model in 2019.
There are no known MAX 9 aircraft with door plugs for the mid-cabin exit operating in Europe or the UK, so please, don’t panic if you realise that you are flying in the window seat of a 737-9 this weekend.
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