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Wednesday, October 4, 2023

Engineer Error Led To A British Airways Boeing 787 Nose-Gear Incident

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The Boeing 787 Dreamliner, carrying the registration G-ZBJB, was involved in an event that damaged the front lower side of the aircraft’s fuselage on June 18, 2021, according to the Air Accidents Investigation Branch (AAIB). The co-pilot and a member of the crew in charge of loading the cargo sustained minor injuries as a result.

What happened to the Dreamliner operated by British Airways?

The 9.4-year-old aircraft was scheduled to fly a cargo flight BA906 between London (LHR) and Frankfurt (FRA) in Germany when it was parked on a stand in Terminal 5 at the London Heathrow Airport.

The ground maintenance crew was attempting to resolve three problem warnings related to the Nose Landing Gear (NLG) doors as the pilots were preparing the aircraft for departure.

The licensed aircraft engineer (LAE) said that the maintenance procedures could be finished in about 40 minutes, at that time the captain was conducting the aircraft walk-around inspection and saw no anomalies, so the crew of loaders carried on loading the cargo onto the aircraft.

When the First Officer was completing the pre-departure checks, he had a minor interaction with the LAE regarding the same issue, shortly after the LAE raised the gear level to the ‘up’ position.

The pilot later recalled hearing the aircraft gear system actuated. It was at that moment that the plane’s nose hit the ground.

How does a down lock pin stop an airplane from retracting its landing gear?

A shock strut, an extension and retraction mechanism, two wheels, a torque link, and a nosewheel steering system are the components of the NLG on a Boeing 787-8 Dreamliner.

A hydraulic NLG lock actuator, part of the NLG extension and retraction mechanism, may lock and unlock a lock link assembly. When the landing gear is selected in an over-center position, this mechanism prevents the landing gear from retracting or extending.

Hydraulic pressure causes the lock link assembly to shift out of the over-center position when the NLG needs to be retracted. This unlocks the NLG and causes it to retract into the wheel bay.

The ground team typically installs a down lock pin to stop the lock link from sliding away from the over-center position when the NLG area requires maintenance.

“The pin is inserted in the down lock hole, aft of the lock link assembly apex pin borehole, to fix the lock link in position and prevent retraction of the NLG even with hydraulic power applied and the landing gear selected to UP,” the AAIB report explained.

The pin used on a Boeing 787 Dreamliner, however, differs significantly from those used on other Boeing aircraft.

“The down lock pin can be easily inserted into the apex pin borehole. […] When it was fitted in this position it made a ‘click’ noise similar to the noise made when fitted into the correct down lock pinhole,” the AAIB report continued.

What was the incident’s cause?

The NLG down lock pin had unintentionally been put in the incorrect location, according to investigators. The engineering team inserted it into the down lock link assembly apex pin bore as opposed to the down lock pin hole. The AAIB speculates that this may have occurred since the two holes are close to one another.

“There were powerful auditory and tactile cues that could easily mislead someone to believe the pin was correctly inserted even when it wasn’t and there were no strong visual indications to distinguish between the correct and incorrect placements,” the report continued.

A particular airworthiness directive (AD), which was made available to engineering teams in January 2020, provided instructions on how to install the down lock pin on a Dreamliner.

While each member of the ground maintenance team had confirmed they were familiar with the latest AD update, investigators found “there was no documented evidence” that the information had been fully considered.

Report findings

Both the First Officer, who was on the flight deck when the aircraft nose hit the ground, and a member of the cargo loading crew near the forward cargo door sustained minor injuries.

The lower front area of the plane also sustained “severe damage,” according to the report.

In reaction to the event, British Airways reportedly examined its procedures for evaluating ADs and safety advisories. In addition, British Airways reportedly made sure that ramp maintenance staff had access to technical information from Boeing via their supplied iPads.

Additionally, the airline has started a review of its incident response guide.

“The operator [British Airways] has introduced a new software application for tech news that has an improved interface including filtering and prioritization functions and requires each page of every article to be displayed before it can be signed,” the report concluded.

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