On June 18th, a British Airways 787-8 (G-ZBJB) had collapsed at Heathrow when it was preparing for a cargo flight to Frankfurt. The UK’s Air Accidents Investigation Branch (AAIB) has issued a bulletin saying human error caused the incident.
The incident took place when crews were performing a “Dispatch Deviation Guide” (DDG) procedure, a procedure that permits the operation of an aircraft, under specific conditions with particular instruments or functions inoperative for a period of time, until recertification can be made.
This procedure required the cockpit landing gear selection lever to be cycled with hydraulic power applied to the aircraft. According to AAIB, “to prevent the landing gear from retracting, the procedure required pins to be inserted in the nose and main landing gear down locks. However, the NLG [nose landing gear] down lock pin was installed in the NLG down lock apex pin bore, which was adjacent to the correct location to install the downlock pin. When the landing gear selector was cycled, the NLG retracted.”
The mechanic who was tasked to handle the landing gear of the 787 was not tall enough to reach a pin needed to lock the landing gear. So, another taller mechanic stepped in. However, the second mechanic put the pin in the wrong recess. The error made the landing gear suddenly retract into a flying position. And the plane collapsed when the hydraulics were tested by an engineer
The incident happened while the plane was being loaded for a cargo flight to Frankfurt. The 787 Dreamliner had been used as a freighter aircraft for some time.
A similar incident has occurred once in the past. In 2018, a 787 had a similar issue, and the reason was once again, the NGL down lock pin was incorrectly inserted.
A service bulletin was provided by Boeing, which instructed the 787 operators to “install an insert into the NLG lock link apex pin bore”. This procedure was made compulsory by FAA in January 2020. Authorities gave 36 months. However, this change wasn’t made in the very 787 that got involved.
Image Credit: “AAIB”