The US National Transportation Safety Board (NTSB) says that the Alaska Airlines aircraft involved in an explosive depressurisation accident earlier this week is structurally sound, but critical safety questions have come to light on the first day of the investigation.
According to evidence and testimony the team has gathered so far, the cockpit door flew open when it should not have, the cockpit voice recorder (CVR) was overwritten before investigators could analyse it, and the airframe’s pressurisation “fail light” illuminated at least three times in the days and weeks leading up to the accident on 5 January.
“There was a lot of damage to [the aircraft’s] panelling, to trim, to the windows, the internal portion of the window, the plastic portion, but the seals in the windows were still intact, insulation was pulled out in some areas,” NTSB chair Jennifer Homendy says during her second briefing on the accident in 24h. “Those are all not critical to the structure of the aircraft.”
Damage was documented inside the aircraft in twelve rows, extending from the very front to the very rear of the cabin. While the cosmetic damage is substantial, NTSB’s experts “looked at the exterior of the aircraft and verified that there is no structural damage to the aircraft,” she adds.
The aircraft, registered N704AL, was operating flight 1282 from Portland, Oregon to Ontario, Canada when the depressurisation occured. The aircraft’s pressurisation systems had experienced issues in recent weeks.
Homendy says a pressurisation “fail light” had illuminated on three previous occasions – on 7 December, on 3 January and on 4 January. Pilots reported those events, and each time the light was tested by maintenance technicians and reset. Additional maintenance was requested ”but that had not been completed at the time of this event”.
She says these incidents were “described as benign”, but, “they are concerning”.
The cause could simply be a faulty light, and may not “have anything to do with this depressurisation”, she adds.
“We don’t know that there was any correlation, it could be entirely separate,” she says.
As a result of the illuminations, however, Alaska Airlines had pulled the aircraft out of its rotation over large bodies of water, for example on flights to Hawaii.
The NTSB team, which arrived in Portland on 6 January, is in its fact-finding phase, Homendy says, which could take months. She adds that no conclusions will be drawn before all information has been gathered and all evidence documented. For this purpose, the experts have divided into four teams: structures, systems, operations and survival factors.
NTSB investigators have so far interviewed the flight deck crew as well as two of the four flight attendants on board. The have yet to speak with passengers.
COMMUNICATION ISSUES
The pilots told the NTSB that when the emergency exit door plug on the left-hand side of the aircraft blew out at around 17:11 local time just after the aircraft had departed Portland, “the cockpit door flew open immediately,” Homendy says. A flight attendant nearby attempted to close it, but needed three attempts.
“[Pilots] heard a bang, they immediately put on their oxygen masks,” she adds. “The flight attendant reports she saw the first officer jolt forward, [she] lost her headset and … the captain had a portion of his headset pulled off.”
“Communication was a serious issue,” Homendy continues. “The flight attendants reported that it was difficult to get information from the flight deck, and the flight deck was having trouble also communicating.”
“The actions of the flight crew were really incredible,” she says. “The flight crew did an excellent job.”
That said, investigators discovered that the cockpit voice recorder (CVR) contained no useful information, leaving them with no flight deck documentation of the moments before the event.
“The cockpit voice recorder was completely overwritten,” Homendy says. “There is nothing on the cockpit voice recorder.”
Currently, the FAA requires cockpit voice recorders to store the last two hours of information, after which the device overwrites the oldest data to maintain a rolling 2h recording. The NTSB has repeatedly recommended the requirement be extended to 25h – consistent with other regions’ requirements, including Europe. The FAA is in the process of evaluating that requirement for new aircraft.
The FAA on 6 January issued an emergency airworthiness directive (EAD) for 171 examples of the Max 9 following the incident. Operators await final instructions for those inspections. Both Alaska and United Airlines - the world’s biggest operator of the type with 79 in its fleet - have grounded all of their Max 9s. Copa Airlines and Aeromexico have also grounded all or portions of their Max 9 fleets.
Late on 7 January, local Oregon media had reported that a homeowner had found the missing door plug in his backyard. Earlier in the day, two cell phones from the aircraft were also found, Homendy says.
