Global Fastener News

While the National Transportation Safety Board works to establish whether the door plug that blew out in midair on a January 5 Alaska Airlines flight was outfitted with the four bolts that prevent it from vertical movement, it’s becoming clear where the responsibility lies.

“The door plug that blew off the Max 9 was removed for repair then reinstalled improperly by Boeing mechanics at the Renton assembly plant,” reports Dominic Gates for the Seattle Times. “That leaves Boeing primarily at fault for the accident rather than its supplier Spirit AeroSystems.”

Boeing issued a bulletin to its suppliers to ensure bolts are properly torqued after multiple airlines reported loose fasteners during inspections of the grounded 737 Max 9, according to a January 17 memo.

The aerospace manufacturer said that it is “imperative” that suppliers meet quality requirements, according to the memo, which was issued weeks after an accident when a panel ripped off of a 737 Max 9 jet in mid-air. The Federal Aviation Administration grounded 171 Max 9 planes with the door panel configuration.

“Ensure that work instructions are mistake-proof and quality is continuously monitored – particularly torquing requirements,” the memo states.

The bulletin suggests suppliers document torque requirements on work instructions, require mechanics to record how much torque is applied when fastening components, and ensure tools are properly calibrated so bolts are properly tightened.

This week, Alaska Airlines CEO Ben Minicucci said the airline found “some loose bolts on many” Max 9s during inspections. Other airlines reported similar findings.

The National Transportation Safety Board (NTSB) is conducting destructive testing of the door plug.

While investigators have been unable to establish whether the door plug was outfitted with the four bolts that prevent it from vertical movement, it is too early to say whether the root cause was missing or wrongly installed bolts, according to NTSB chair Jennifer Homendy.

“We’re also looking at the seal. We’re looking at, was there any sort of structural flexing of the aircraft?” Homendy stated. “It may not be bolts.”

Homendy’s comments comes days after the Federal Aviation Administration announced that it will increase oversight of Boeing and audit production of the 737 Max 9 jetliner. The FAA will determine whether Boeing and its suppliers followed approved quality procedures.

The FAA also said it’s reconsidering its longstanding practice of relying on aircraft manufacturer employees to perform some safety analysis of planes.

The catastrophic failure occurred when a door plug blew off a new Alaska Airlines Boeing 737 Max 9 at 16,000 feet, imperiling 171 passengers and 6 crew members.

Four “stop” bolts should have prevented the door plug from moving upward and coming off the plane, according to National Transportation Safety Board chair Jennifer Homendy.

But the bolts were not on the recovered door plug, and investigators are trying to determine whether they were there to begin with.

“We don’t know if they were there or if, again, they came out during the violent explosive decompression event,” Homendy stated.