The Hong Kong Air Accident Investigation Authority (AAIA) has released its preliminary report on the airACT 747 freighter that veered off the runway on 20 October, striking a security vehicle and pushing it into the sea, killing both occupants.
The 747 also went through the airport perimeter fence into the sea. The aircraft’s crew of four were able to safely evacuate, while the aircraft was damaged beyond repair.
As with all preliminary accident investigation reports, the AAIB only provides factual information. The final report, usually available approximately 12 months after an accident, will detail what investigators believe to be the probable cause.
Notable findings
The preliminary report notes that the aircraft was dispatched per the Minimum equipment list with Engine number 4 thrust reverse inoperative. The first officer was the pilot flying, the captain was the pilot monitoring.
Upon landing the speed brake lever was extended “with the appropriate crew call.” Reverse thrust was deployed on engines 2 & 3 at approximately 95% of N1. Engine 1 was selected to idle reverse.
The crew received an AUTOBRAKES message on the Engine-indicating and crew-alerting system (EICAS) screen (exact time is not noted in the report), and the autobrake was disarmed, with the crew calling “manual braking.” The captain took control of the aircraft at this time.
The time stamps in the image above are taken from the preliminary report based on the aircraft’s Flight Data Recorder. We have collated those times to the ADS-B data sent from the aircraft’s transponder to provide a visual reference.
At 19:52:30 UTC (03:52:30 local time), Engine number 4 “accelerated to 90% N1 forward thrust.” The selected thrust reversers (ENG 2 & 3) were stowed at 19:52:35.
Engine number 4 continued to accelerate, achieving 106% of N1 at 19:52:36 and reaching 107% of N1 by 19:52:42.
Reverse thrust was applied on Engine number 2 at 19:52:41. Thrust reversers on Engines 1 & 3 were also deployed, but no specific time is noted on the deployment of these in the report.
Investigative next steps
The AAIA says it will continue collecting data with particular focus on aircraft systems and performance, maintenance records, flight crew qualifications and experience, human factors, and Safety Management Systems.
Specifically, investigators note a focus on “technical issues related to aircraft systems and performance, including the aircraft’s speed, system status and operational control at the time of the accident, as well as conditions and performance of the aircraft engines, the forward movement of the Number 4 engine thrust lever, the landing gears and the associated brake systems, etc.”
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