21st of June 2021
A Boeing 787-9 was being prepared for a domestic flight from Sydney to Perth, Australia. At approximately 07.45 lt (local time) the aircraft was towed to the gate. Onboard the aircraft was a licensed engineer and an engineer under training When the aircraft arrived at the gate, chocks were replaced at the aircraft wheels, and the tow truck was disconnected.
Main Landing Gear Downlock Pin Locations (Source & © ATSB)
A ground crew member then proceeded to remove the nose landing gear downlock pin and subsequently one main landing gear downlock pin from the left-hand main landing gear while another ground crew member removed the main landing gear downlock pin from the right-hand main landing gear. The three landing gear downlock pins were then stowed in their storage location in the Electrical Equipment Centre (EEC), just aft of the nose landing gear. This was verbally confirmed to the licensed engineer in the fligthdeck.
When the licensed engineer and his colleague left the aircraft they walked toward the nose landing gear and verified the nose landing gear downlock pin was removed, looking towards the main gears he did not see any REMOVE BEFORE FLIGHT flags from the main landing downlock pins, he concluded they were removed. A subsequent tactile check (the steps used were tp small for a visual check) of the storage location for the landing gear downlock pins confirmed they were in their storage location.
The landing gear downlock pin storage location in the EEC (Source © ATSB)
When the crew (captain, co-pilot and relief pilot) arrived at the aircraft they checked the aircraft's technical log and observed that the removal of the landing gear downlock pins was recorded and certified in the technical log. The relief pilot performed the external inspection of the aircraft in accordance with the Flight Crew Operations Manual (FCOM) and did not find any anomalies. The rest of the pre-flight preparations were completed without further remarks. With all the passengers on board the aircraft, the aircraft was pushed back from the gate at 10.25 lt. The aircraft taxied to runway 16R and received its take-off clearance around 10.30lt after which the aircraft accelerated down the runway and lifted off. At 10.32 with a positive climb established the landing gear was selected up. 40 seconds later a GEAR DISAGREE caution was displayed on the Engine Indication and Crew Alerting System (EICAS) accompanied by an aural alert. Indicating there was disagreement between the landing gear selector position and the actual landing gear position.
A review of the gear indications revealed that the nose landing gear had retracted, but both main landing gears were indicating "In Transit". ATC was informed about the landing gear issue after which the aircraft received vectors away from the airport while they levelled off at 9000ft, to troubleshoot the issue.
The indication as seen by the crew After completing the relevant checklists (Source & © ATSB) the crew decided to return to Sydney.
The landing gear indicated all three gears were down and locked when selected down and therefore the crew declined the offer from ATC to have the emergency services on standby. An uneventful landing was made at 11.06 lt, and subsequently, the aircraft taxied to a parking stand. After arriving on the stand engineering staff carried out an inspection of the main landing gear, it then became apparent that two landing gear downlock pins were still installed, one in each main landing gear.
The landing gear downlock pins (gear pins) are used to prevent inadvertent gear retraction during maintenance or towing operations. The 787 has five gear pins, one for the nose gear and two for each main landing gear.
The incident was investigated by the Australian Transport Safety Bureau (ATSB), and on the 16th of November 2021, they issued their final report, which is available for your review by clicking here.
They concluded that two of the five landing gear pins were not removed as per the operator’s procedures, nor identified by engineering, flight crew or dispatch during pre-departure checks. This resulted in the aircraft departing without the functionality to retract the main landing gear,
Boeing 787 main landing gear extension and retraction test, not on the incident aircraft (Source Youtube.com / Vishnu Ettammalillath)