Description

On 12 May 2022, an Airbus A319 (B-6425) operated by Tibet Airlines on a scheduled domestic passenger flight from Chongqing to Nyingchi as TV9833 rejected its takeoff from runway 03 when an unintended rudder input occurred just before V1. As a result, the aircraft then veered off the left side of the runway and passed over two elevated manhole covers and a runway 03 rapid exit taxiway (RET) with an elevated edge before crossing an open ditch. Both engines and both main landing gear assemblies were detached. As the aircraft subsequently came to a stop, a fire started but an emergency evacuation of the 122 occupants was accomplished with only minor impact and/or burn injuries to four passengers and two crew members. The extensive damage to the airframe resulted in a hull loss. 

The aircraft after completion of the emergency evacuation. [Reproduced from an unidentified contemporary source]

Investigation

An Accident Investigation was carried out by the Aviation Committee of the Southwest Region of the Civil Aviation Administration of China (CAAC-SW).The cockpit voice recorder (CVR), flight data recorder (FDR), and digital recorder (DAR) were removed from the aircraft and their relevant data were downloaded and confirmed valid. Relevant recordings from the airport surveillance video system were also available.

The training captain in command joined the airline in 2015 and was occupying the left pilot seat as pilot monitoring (PM) with a total of 16,296 hours flying experience, of which 15,939 hours were on type. The pilot flying (PF) first officer had joined the airline in 2019 and had a total of 2,205 hours flying experience, of which 686 hours were on type. An observer captain with total of 10,202 hours flying experience, of which 9,567 hours were on type was occupying a supernumerary crew seat in the flight deck and under applicable procedures was responsible for “monitoring the performance of the operating flight crew and calling out any deviations from standard operating procedures (SOPs) and any missed radio calls."    

What Happened

The takeoff had proceeded normally with the first officer using rudder as required to maintain directional control as the speed increased so that the aircraft remained on the centreline of the 60 metre-wide runway. Directional control by the first officer had kept the aircraft on the runway centreline, but as the 145 KIAS V1 was approached, the first officer detected a sudden left rudder pedal movement and the aircraft veered to the left. Without speaking and with the aircraft now heading towards the left hand runway edge and the rudder deflection to the left increasing through 13°, the captain took over control and rejected the takeoff after a ground run of around 1,500 metres.

Both thrust levers were moved to flight idle, the speed brakes were raised, and autobraking took effect but left rudder deflection increased and the aircraft continued to turn to the left. Two seconds later, the recorded groundspeed reached a maximum of 148 knots with the left rudder input still increasing and approaching maximum travel. The autobrake disconnected and symmetrical dual reverse thrust was selected to maximum.  

After a further two seconds with the groundspeed now beginning to reduce, the nose landing gear departed the left hand runway edge with full left rudder deflection still being applied. The left rudder input then began to reduce as did the ground speed. As the open ditch was crossed, rearward deflection of the nose landing gear and impact detachment of both engines and both main gear assemblies resulted in a 7° nose down attitude. Shortly after this, all data recording ceased.

Twelve seconds after leaving the runway, the aircraft came to a stop on taxiway ‘J’ at its intersection with an earlier runway 20 RET and an access road, with the aircraft nose aligned 65° to the left of the runway 03 centreline. This position was 192 metres laterally from the runway 03 centreline and the track to that point after departing the runway was 415 metres.

The first rescue and firefighting services (RFFS) vehicle reached the scene just after two minutes. The fuselage and under fuselage fire was then extinguished in a recorded time of just under a minute. The emergency evacuation which, in the absence of electrical power, was initiated by the senior cabin crew member (SCCM), calling “evacuation” three times, was recorded as having been completed in 109 seconds using only door L2 where the slide deployed normally.

Editors Note: The Official Report does not contain any pictorial or diagrammatic illustrations.

Impact and fire damage to the aircraft was extensive and included the following:

• The two engines detached by transit across the open ditch were internally damaged 
• Both the nose and main landing assemblies were damaged beyond repair
• The right wing sustained major damage, the left wing less so. 
• The flames from the fire which began in the left engine upper pylon area spread towards the nose of the aircraft and affected the 1L door and its slide as well as the fuselage skin between frames 9 and 31. 

No damage to or malfunction of any part of the airframe or aircraft systems that could have contributed to the directional control deviation which occurred was found.

Discussion

The operating captain said that just as V1 was approached, unspecified items placed “on the side console” had fallen onto his left leg and that on looking down to find the sliding object, he concluded that he had “unconsciously touched the left rudder pedal” and on looking up again saw that the direction of the aircraft had deviated but without immediately recognising the cause. He accepted that the placing of loose items on the side console was contrary to SOPs. He also accepted he had not made the mandatory call required to take control from the first officer which had left the latter “unclear as to their intentions."

It was also noted by the investigation that the seating position of the observer captain immediately behind the operating captain was not conducive to effective monitoring, and that a much more suitably located crew seat had been available. It was concluded that the observer had “failed to perform his observer duties." However, the adaptability of the cabin crew in effectively organising the evacuation was commended.

Having noted the extent of the damage caused to the aircraft by its passage across the open drainage ditch and found that it was only 90 metres away from the edge of runway 03/21, it was confirmed that this ditch was permitted as located in accordance with the applicable regulatory requirements at the time.

Conclusion

Based on the injuries sustained during the emergency evacuation and the extensive damage caused to the aircraft, it was concluded that the event “constituted an accident caused by the flight crew” and therefore classifiable as a "general aviation accident caused by errors."

Seven Safety Recommendations were made based on the Findings of the Investigation as follows:

• that Tibet Airlines implement the main responsibility of safety management, comprehensively sort out the closed-loop situation of the bureau's inspection and the company's self-inspection problem rectification, effectively improve the effectiveness of the safety management system, and ensure that there are no blind spots in risk control. [SWSW_AAR_2022_01-001]
• that Tibet Airlines improve their training system, use data as a driver to identify technical weaknesses, implement targeted training, strictly enforce inspection standards, and enhance their ability to handle special situations in emergencies. [SWSW_AAR_2022_01-002]
• that Tibet Airlines Crew Resource Management (CRM) Training for crew members should follow the relevant requirements of the "Guidelines for Flight Crew Members" (AC-121-FS-41R1) in order to effectively implement CRM training and enhance CRM competence. [SWSW_AAR_2022_01-003]
• that Tibet Airlines, in accordance with the requirements of the "Guiding Opinions on the Construction of Work Style of Civil Aviation Safety Practitioners" and the "Guidelines for the Construction of a Long-term Mechanism for the Work Style of Civil Aviation Safety Practitioners," refine their assessment standards, enrich their assessment methods and means, and improve the long-term mechanism for work style construction. [SWSW_AAR_2022_01-004]
• that Tibet Airlines strengthen manual training and safety for flight crews cultural education and refine supervision and management measures during operation. [SWSW_AAR_2022_01-005]
• that Chongqing Airport conduct a comprehensive special assessment of the levels of all runways and eliminate vertical surfaces of structures within the Runway End Safety Area (and) if it is found that elimination measures need to be taken, timely rectification should be carried out. [SWSW_AAR_2022_01-006]
• that the Civil Aviation Administration refine the regulations in respect of relevant requirements for flight deck cleanliness, standardising of items permitted there and their placement, fixation and use so as to avoid affecting flight control and operational safety. [SWSW_AAR_2022_01-007]

The Final Report of the Investigation was published in Chinese only and released on 6 June 2024. This Summary is based on an unofficial translation.

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