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Engineers' Laurel and Hardy moment caused British Airways 787 to take an accidental knee

A tale of two holes and two mechanics of two different heights

A British Airways Boeing 787's landing gear collapsed during a botched test after a short mechanic asked a taller co-worker to insert a lock-out pin into a hole he couldn't reach – only for the second mechanic to put it in the wrong place.

The Laurel and Hardy-style failure was detailed in a bulletin from Britain's Air Accidents Investigation Branch (AAIB), explaining why the 787's nose landing gear (NLG) was accidentally retracted during maintenance at Heathrow Airport in June.

"To prevent the landing gear from retracting, the procedure required pins to be inserted in the nose and main landing gear downlocks. However, the NLG downlock pin was installed in the NLG downlock apex pin bore which was adjacent to the correct location to install the downlock pin," said the AAIB in its report.

British Airways Boeing 787 G-ZBJB after the nose landing gear retraction accident. Crown Copyright/AAIB

British Airways Boeing 787 G-ZBJB after the nose landing gear retraction accident (Crown Copyright/AAIB/licensed under OGL)

The 787, G-ZBJB, was scheduled to operate a cargo flight on 18 June. When its pilots arrived early that morning they found ground engineers already working on the aircraft, pushing back its scheduled departure by 40 minutes.

Engineers were trying to clear error messages in the 787's onboard fault recording system about one of the NLG's door-closed solenoid valves. Clearing the message involved fitting lock-out pins to the airliner's undercarriage to prevent it from moving, starting the hydraulic pumps and cycling the gear lever in the cockpit up and down. Without the pins, the landing gear would retract.

Unfortunately for British Airways, a Laurel and Hardy moment resulted in a very expensive blunder when the NLG unexpectedly retracted during the procedure. Two mechanics were sent to fit the downlock pins to the landing gear before confirming to a colleague in the cockpit that the gear was ready.

"As [Mechanic] 1 was not tall enough to reach the NLG locking pin hole without steps, he pointed to the location of the hole and [Mechanic] 2 fitted the NLG locking pin," recounted the AAIB. Yet Mechanic 2 had fitted the pin to a very similar hole (the NLG downlock apex bore) next to the correct location.

Boeing 787 nose landing gear lockout pin location. Crown Copyright/AAIB

Boeing 787 nose landing gear lockout pin location (Crown Copyright/AAIB/licensed under OGL)

An obvious human factors issue, the risk of fitting the downlock pin into the wrong hole had been identified years before after a similar incident [PDF] – yet aviation safety authorities gave airlines a three-year deadline from December 2019 (January 2020 in the UK, then under the EU Aviation Safety Agency) to fit a sleeve to the wrong hole, preventing the downlock pin from being inserted.

Predictably, the modification hadn't been carried out on G-ZBJB and the results of the gear retraction were bad.

"The aircraft sustained damage to the lower forward fuselage, NLG doors and both engine cowlings, which had also struck the ground. Door 2L had been severely damaged by contact with the stairs positioned at the door aperture as the aircraft sank onto its nose," said the AAIB.

Some of the people aboard the airliner suffered "minor" injuries as the nose crashed to the ground.

BA's 787s have had fairly uneventful service lives, although in April an in-flight fire was caused aboard one by a Club Class passenger dropping her iPhone XR into her power-operated lie-flat seat. ®

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