Speaking late Monday about the fuselage explosion on Alaska Airlines Flight 1282, National Transportation Safety Board Chair Jennifer Homendy ruled out the possibility of negligence on the part of the airline.
Instead, the NTSB’s initial findings focused squarely on the manufacture and installation of the door stop that fell out 737 Max 9 aircraft, leaving a large gap in the passenger cabin wall and causing the aircraft to rapidly depressurize at 16,000 feet.
That leaves supplier Spirit AeroSystems in Wichita, Kan., on the hook to install the door plug and Boeing in Renton to perform a final inspection of the component before it is sealed behind the insulation and sidewall.
Hope that this incident was a one-time aberration was dashed Monday when both Alaska and United found loose bolts on door seals during inspections of other MAX 9 planes. This now looks more like a serious factory quality control issue for Boeing.
The plug is a plate used to close the fuselage opening of the optional emergency exit door that is only used by a few airlines with high density seating. Most airlines, including Alaska and United in the US, don’t have a door there, instead installing a plug that appears to passengers inside as just another window.
The focus of discussion at Monday’s news conference, after investigators examined both the plane and the fallen door seal — which was found Sunday in a Portland teacher’s backyard — were four missing screws that should have kept the door seal in place. .
“We don’t know if there were screws in there, or if they were missing and left when the door plug came loose…during the violent explosive decompression,” Homendy said.
A statement issued by the Federal Aviation Administration on Tuesday indicated that it may take some time for the Max 9 to return to the skies.
The FAA confirmed that Boeing on Monday sent initial inspection instructions to airlines that were inadequate. Those instructions would have to be reviewed by Boeing and approved by the FAA.
“The safety of the public, not speed, will determine the timeline for returning the Boeing 737-9 MAX to service,” the FAA said.
Alaska Airlines said Tuesday it is still awaiting final approved inspection and maintenance instructions for its fleet of 65 MAX 9 aircraft.
“Until then, the Boeing 737-9 MAX fleet will remain grounded,” Alaska said.
Sad Boeing rally
On Tuesday, as Boeing tried to assess the impact of the accident, top executives gathered in Renton for an employee safety meeting.
CEO Dave Calhoun, new Chief Operating Officer Stephanie Pope, Chief Safety Officer Mike Delaney, and Stan Deal, CEO of the Commercial Aircraft Division, spoke at noon to about 500 employees at the plant where the MAX planes are assembled. The meeting was broadcast online to all Boeing employees.
A 5-minute video posted by Boeing of Calhoun’s somber remarks at the meeting shows him pausing and appearing on the verge of choking as he talked about seeing images of the hole in the fuselage with passengers nearby.
“I have children, I have grandchildren, and so do you,” Calhoun told employees. “These things are important. Every detail is important.”
He said Friday’s explosion “shocked me to the bone.”
He described the incident as a “reminder of the seriousness with which we have to take our business” and said it created a “very anxious moment” for Boeing’s airline customers.
He said Boeing would try to restore airlines’ trust through “our willingness to work directly and transparently with them, and make sure they understand that every plane with Boeing’s name in the sky is in fact safe.”
NTSB preliminary findings
At the NTSB’s press conference Monday evening, Homendy provided more details about how terrifying the incident was for those aboard Flight 1282.
She said emotional interviews with flight attendants showed they had suffered “a lot of trauma.”
The flight attendants told investigators that they were unable to communicate with each other and understand what was happening because of the noise. Those who were in the back of the plane near the hole that opened up couldn’t even see it from their positions.
“It was very terrifying” for the cabin crew, Homendy said, and she appealed to the media to give them space and time to recover.
The NTSB’s first conclusion, after examining the plane and the 63-pound door plug, was that the four screws that were supposed to prevent the plug from moving outward must have been either missing, installed incorrectly, or broken.
On board, six small brackets on either side of the door frame — 12 in all, called “stop fittings” — line up with 12 similar stop pads on the door seal.
When the passenger compartment is pressurized, the stop pads firmly press the stop fittings and lock the door plug tightly against the fuselage.
To service a door plug, it is opened by moving the plug up so that the pads on the door plug rise above the stop fittings on the door frame, which then allows the plug to move out.
There are pins, similar to the screws in the pictures, that slot through the center of the stop fittings. But these are only to help with door plug alignment; They are not structurally strong.
What prevents the door plug from blowing into the air are four screws, two at the top and two at the bottom that are attached to locking wires, which prevent it from moving upwards.
The top screws pass through the guide tracks on both sides of the door plug to prevent the swivel screws on the fuselage frame from sliding out of the guides.
The bottom bolts go through two posts at the bottom of the door which prevents the springs below from pushing the door plug up.
With these screws in place, the plug cannot move up and the 12 stop fittings press against the stop pads to secure it.
“Testing today showed that the door had in fact moved to the top,” said Clint Cruickshanks, a structural specialist at the NTSB. “All 12 terminals were disconnected allowing it to exit the fuselage.”
A break was found in both cylindrical tracks on the door seal. No bolts found.
“We have not yet recovered the four screws that restrict (the door plug) from its vertical movement,” Crookshanks said. “We have not yet determined whether they are there.”
Homendy added that microscopic examination of the door seal at the NTSB laboratory in Washington, D.C., will determine from scratch marks whether screws have been installed or not.
Alaska exempted from the decision to fly the plane
While those questions loom, Homendy explained why she wasn’t concerned with the many low-pressure incidents before Friday’s accident.
Intermittent warning lights indicating a brief drop in cabin pressure appeared during flights of the new MAX 9 jet on December 7 and then again on January 3 and 4, the two days before the accident.
As a result, Alaska decided not to fly the plane on long-range flights over water. So it can fly from Portland to California, but not to Hawaii.
Many were shocked to read about this decision in press reports and expressed their anger on social media.
But Homendy said she believes those three incidents are likely unrelated to the blown door plug and that Alaska’s decision makes sense.
She explained that the MAX cabin pressure system is a redundant triple system, with primary and secondary computer controllers supported by a manual option for pilots.
In the previous three incidents when the warning lights came on, the main control unit had failed but the secondary system had started working, without any major effect.
Investigators will continue to examine pressure logs, but “at this time, we have absolutely no indications that this is in any way related to the door seal expelling and rapid decompression,” Homendy said.
She said Alaska’s decision to restrict the aircraft from long-haul routes over water was not required by regulations but was a precaution taken voluntarily by the airline to provide an additional margin of safety when any critical systems showed any sign of a recurring problem.
The logic is that if a plane had any trouble flying from Portland to California, it could easily find a place to land. If something goes wrong in the middle of the ocean, it’s even more serious.
The MAX is certified to fly on routes that take more than three hours from the nearest airport.
The policy of prohibiting it from doing so at any sign of a problem with the system is “an additional step taken by Alaska Airlines,” Homendy said.