NTSB Chair Jennifer Homendy has briefed the media in Portland, Oregon on the NTSB investigation involving Alaska Airlines Flight 1282 on a Boeing 737-9 MAX.
The first full day of the investigation has seen the NTSB carry out the inspection of insitu structure and fittings on board the aircraft.
Aft-cabin door plug assembly
The investigation centers around the hinged door plug assembly which detached from the fuselage during flight. The assembly in question has dimensions of 26 x 48” and weighs approximately 63 pounds.
It bolts to the fuselage recess via a set of stop fittings on each side of the plug panel. The assembly is hinged at two points at the bottom and opens approximately 15 degrees outwards to permit inspections.
Previous Warning Light Indications
It was noted that the Auto Pressurisation Fail Light had illuminated on the flight deck on three separate occasions prior to the depressurisation incident. Flight crew noted the activation of the warning light during a flight on December 7, and then on two subsequent flights on January 3 and 4.
In each of those three instances, flight crew carried out procedural checks to confirm the issue. In each of these cases, the situation was described by the NTSB as “benign”, with no apparent problems arising.
At this stage in the investigation, the NTSB could not confirm whether there was any correlation between the three warning light indications and the depressurisation incident caused by the separation of the door plug in flight on January 5.
It was noted that the operator had subsequently put into place an ETOPS (Extended-range Twin-engine Operations Performance Standards) restriction, preventing the aircraft in question from operating the overwater flights as a precautionary measure.
Interior Non-structural Damage
The investigation noted damage to non-critical interior cabin trim at seat rows 33,32, 31, 27, 26, 25, 12, 11, 4, 3, 2 and 1. Seat damage was also noted at rows 26 and 25.
The investigation team further observed that there was no structural damage to the exterior of the Boeing 737 MAX 9 aircraft whatsoever.
The 178 seats available in the aircraft, 171 were occupied. There were no occupants assigned to seats 26a and 20b, which were immediately adjacent to the left-hand side aft-cabin door plug assembly.
Jennifer Homendy commended the subsequent actions of the Alaska Airlines cabin crew, noting in particular the attention and care given by crew members to four unaccompanied minors who were aboard the aircraft at the time of the incident.
The exclusive decompression which occurred when the door plug assembly separated from the fuselage was described as ‘very violent’. The ferocity of the depressurisation event caused the flight deck security door to fly open immediately.
A forward cabin crew member managed to close the flight deck door after making three attempts.
Difficulties with communications between the flight deck and the passenger cabin were reported. The decompression event ripped the headset off the First Officer and partially removed the Captain’s headset.
Location of 737 MAX Missing Door Plug
The missing aft fuselage door plug assembly was subsequently located today after a man in Portland reported finding the component in his garden.
Two cell phones which belonged to passengers on board the flight were also subsequently recovered.
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