NTSB focuses on jet assembly work by Boeing and supplier after Alaska Airlines blowout

SEATTLE — Speaking late Monday about the fuselage blowout on Alaska Airlines flight 1282, National Transportation Safety Board chair Jennifer Homendy discounted the likelihood of negligence by the airline.

Instead, the initial NTSB findings focused squarely on the manufacture and installation of the door plug that fell off the 737 MAX 9 aircraft, leaving a gaping hole in the passenger cabin wall and causing the plane to rapidly depressurize at 16,000 feet

That leaves supplier Spirit AeroSystems of Wichita, Kan., on the hook for installing the door plug and Boeing in Renton for final inspection of the component before sealing it behind insulation and sidewall.

The hope that this incident might be a one-off aberration was dashed Monday when both Alaska and United found loose bolts on door plugs while inspecting other MAX 9s.

The plug is a panel used to seal a fuselage cutout for an optional emergency exit door that is used only by a few airlines with high-density seating. Most airlines, inlcuding Alaska and United in the U.S. don’t have a door there, instead installing the plug, which appears to passengers inside as just another window.

The focus of the discussion in the Monday news conference, after investigators examined both the aircraft and the door plug that fell off — it was found Sunday in the backyard of a Portland teacher — was four missing bolts that should have kept the door plug in place.

“We don’t know if there were bolts there, or if they are just missing and departed when the door plug departed ... during the violent explosive decompression,” Homendy said.

On Tuesday a statement from the Federal Aviation Administration suggested the return of the MAX 9 to the skies may take a while.

The FAA confirmed that Boeing on Monday sent out initial inspection instructions to airlines that were inadequate. Boeing will have to revise those instructions and the FAA approve them.

“The safety of the flying public, not speed, will determine the timeline for returning the Boeing 737-9 Max to service,” the FAA said.

Alaska Airlines said Tuesday it still awaits those approved final inspection and maintenance instructions for its fleet of 65 MAX 9s.

“Until then, the Boeing 737-9 MAX fleet will remain grounded,” Alaska said.

A somber Boeing gathering

On Tuesday, as Boeing attempted to take stock of the impact of the accident, top executives gathered in Renton for an employee safety meeting.

CEO Dave Calhoun, the new Chief Operating Officer Stephanie Pope, Chief Safety Officer Mike Delaney and Stan Deal, CEO of the Commercial Airplane division, all spoke at noon before about 500 employees in the factory where the MAX is assembled. The meeting was webcast to all Boeing employees.

A 5-minute video Boeing posted of Calhoun’s somber remarks at the meeting show him pausing momentarily and appearing on the point of choking up as he talked about seeing photos of the hole in the fuselage with passengers nearby.

“I’ve got kids, I’ve got grandkids and so do you,” Calhoun told the employees. “This stuff matters. Every detail matters.”

Friday’s blowout “shook me to the bone,” he said.

[When Alaska Flight 1282 blew open, a mom went into ‘go mode’ to protect her son]

He called the accident “a reminder of the seriousness with which we have to approach our work” and said it has created “a very anxious moment” for Boeing’s airline customers.

He said Boeing will try to restore airline confidence by “our willingness to work directly and transparently with them, and to ensure they understand that every airplane that Boeing has its name on that’s in the sky is in fact safe.”

Initial NTSB findings

At Monday night’s NTSB news conference, Homendy provided more details on just how frightening the incident was for those on board flight 1282.

She said emotional interviews with the flight attendants showed they are working through “a lot of trauma.”

The flight attendants told investigators they were unable to communicate with one another and understand what was going on due to the noise. Those in the rear of the plane nearest the hole that opened up couldn’t even see it from their positions.

“It was pretty 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 inspection of the aircraft and of the 63 pound door plug is that four bolts that should have prevented the plug from moving outward must have either been missing, misinstalled or broken.

On the aircraft, 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 plug.

When the passenger cabin is pressurized, the stop pads press tightly against the stop fittings and seal the door plug tight against the fuselage.

For maintenance of the door plug, it’s opened up by moving the plug upward so that the pads on the door plug rise above the stop fittings on the door frame, which then allows the plug to move outward.

There are pins, which look like screws in the photos, that slot through the center of the stop fittings. But these are purely to help align the door plug; they aren’t structurally strong.

What prevents the door plug from blowing out in the air are four bolts, two at the top and two at the bottom secured with lock wires, that prevent it from moving upward.

The upper bolts go through guide tracks on either side of the door plug to prevent roller pins on the fuselage frame from slipping out of the guides.

The lower bolts go through two shafts at the bottom of the door that prevent springs below from pushing the door plug upward.

With those bolts in place, the plug cannot move upward and the 12 stop fittings press against the stop pads to hold it in.

“The exam today has shown that the door in fact did translate upward,” said NTSB structures specialist Clint Crookshanks. “All 12 stops became disengaged allowing it to blow out of the fuselage.”

Both roller tracks on the door plug were found to have fractured. The bolts have not been found.

“We have not yet recovered the four bolts that restrain (the door plug) from its vertical movement,” Crookshanks said. “And we have not yet determined if they existed there.”

Homendy added that microscopic examination of the door plug at the NTSB lab in Washington, D.C., will determine from scratch marks whether the bolts were installed or not.

Absolving Alaska’s decision to fly the plane

While those questions loom, Homendy explained why she is much less concerned about several depressurization incidents before Friday’s accident.

Intermittent warning lights indicating a brief reduction in cabin pressurization had occurred on flights of this new MAX 9 on Dec. 7 and then again on Jan. 3 and 4, the two days before the incident.

As a result, Alaska decided to not fly the jet on long-range trips over water. So it could fly from Portland to California, but not to Hawaii.

Many were shocked to read of that decision and expressed outrage on social media.

[Alaska Airlines’ decision not to ground Boeing jet despite warning signs comes under scrutiny]

But Homendy said she believes these three incidents are likely unrelated to the door plug blowout and that Alaska’s decision makes sense.

She explained that the MAX cabin pressurization is a triple redundant system, with primary and secondary computer controllers backed up by a manual option for the pilots.

On the three previous incidents when warning lights illuminated, the primary controller had gone down but the secondary system kicked in, with no significant impact.

Investigators will continue to examine the pressurization logs, Homendy said, but “at this time, we have no indications whatsoever that this correlated in any way to the expulsion of the door plug and the rapid decompression.”

And she said Alaska’s decision to restrict the jet from long-range routes over water was not required by regulations but was a precautionary measure the airline takes voluntarily to provide an additional safety margin when any important systems show any sign of a repetitive problem.

The logic is that if a plane gets into any trouble flying from Portland to California, it can easily find a place to land. If something goes wrong mid-ocean, that’s much more dangerous.

The MAX is certified to fly routes that take it more than three hours from the nearest airport.

Homendy said the policy to restrict it from doing so at any sign of a system issue is “an extra step that Alaska Airlines put in place.”