A preliminary investigation into last month’s deadly runway excursion at Hong Kong International Airport (HKIA) suggests an abrupt and unexpected surge in thrust from one engine caused a Boeing 747 freighter to fatally veer off the tarmac, killing two airport workers. Released late Tuesday by the Air Accident Investigation Authority (AAIA), the initial report details how the Turkish-operated ACT Airlines cargo flight, chartered by Emirates, lost directional control moments after landing, culminating in a catastrophic collision.
The October incident involved a Boeing 747 freighter operating a flight from Dubai to Hong Kong. While the landing phase initially proceeded normally, the aircraft was dispatched with an inoperable thrust reverser on engine No. 4—a condition permissible under standard aviation safety regulations.
Asymmetry Challenges Directional Control
According to AAIA findings, after the first officer executed the landing, and the autobrake system disengaged, the captain assumed control of the aircraft. Within seconds of this handover, engine No. 4, situated on the aircraft’s far-right wing, unexpectedly advanced its power setting. Investigators noted the engine spooled up rapidly, reaching approximately 90% thrust before surging further to between 106% and 107% over a crucial 12-second period.
As this sudden, massive surge developed on the right side, the flight crew deployed the thrust reversers on the remaining three functioning engines in an apparent attempt to slow the jet. However, the resulting asymmetric thrust—powerful forward force on one side countered by reverse braking on the other—made maintaining control virtually impossible. The aircraft departed the left side of the runway at high speed.
Deadliest HKIA Incident in Decades
The uncontrollable trajectory led the jumbo jet to collide forcefully with an airfield security vehicle operating near the runway’s edge. The impact forced the service vehicle into the sea, resulting in the fatal injuries of the two airport security personnel inside. Authorities have called the event the city’s deadliest aviation accident in more than a quarter-century.
While all four crew members aboard the freighter survived the accident, the massive impact destroyed the airframe. Photographs and structural assessments show the tail section of the 747 separating completely upon impact.
Aviation safety experts reviewing the preliminary data highlighted the highly irregular nature of the engine acceleration after landing. Experts noted that significant asymmetric thrust, especially at such high percentages relative to typical ground idle settings, rapidly compromises a pilot’s ability to maintain a straight line, despite the crew’s immediate action to utilize thrust reversers elsewhere.
Scrutiny Shifts to Systems and Maintenance
The AAIA stressed that this report is preliminary, and the root cause of the engine’s unexpected spool-up remains undetermined. The ongoing investigation is focused on gathering crucial technical evidence, including detailed systems data, engineering and maintenance records for both the engine and its control systems, and comprehensive information regarding crew qualifications and experience.
Boeing, the aircraft manufacturer, directed all inquiries regarding the preliminary findings to the AAIA. Neither Emirates nor ACT Airlines has issued public comments regarding the report’s content.
Hong Kong’s Transport and Logistics Bureau has committed to adhering to international aviation investigation standards, aiming to publish the comprehensive final report outlining the definitive factors contributing to the tragedy within one year. This final document will determine systemic failures, maintenance oversights, or operational errors that may have contributed to the catastrophic engine acceleration.