Air China 428 terrain alert at Hong Kong
Air China 428 makes a premature turn after takeoff, narrowly avoiding Lantau Island's mountainous terrain.
Summary
Shortly after departing Hong Kong International Airport, Air China 428 deviated from its departure procedure by turning left toward high terrain. The air traffic controller recognized the danger and issued urgent instructions for an immediate right turn and an expedited climb. The aircraft narrowly cleared the peaks of Lantau Island before continuing safely to its destination.
Analysis
On June 5, 2017, Air China flight 428, an Airbus A330-300, departed from Runway 25 Left at Hong Kong International Airport (VHHH) bound for Chengdu. Under the standard instrument departure (SID) procedures for that runway, aircraft are required to maintain a specific heading to avoid the rugged, mountainous terrain of Lantau Island, which features peaks reaching nearly 3,000 feet. Shortly after takeoff, the flight crew initiated a left turn significantly earlier than the procedure dictated, placing the heavy aircraft on a direct path toward the mountains.
The recording captures the Departure controller’s immediate recognition of the deviation. As the aircraft entered a zone that triggered a Minimum Safe Altitude Warning (MSAW), the controller's tone shifted from routine to urgent. The controller repeatedly commanded the pilot to "turn right immediately" and "expedite climb," specifically citing "Terrain ahead." This is a critical safety intervention, as the aircraft was flying at approximately 3,000 feet in an area where Lantau Peak stands at 3,064 feet.
For non-experts, it is important to understand that Hong Kong is one of the most challenging airports in the world due to its geography. Departure procedures are designed with "climb gradients" and specific turn points to ensure a "buffer" between the aircraft and the mountains. By turning early, the Air China crew bypassed these safety buffers, relying entirely on the controller's vigilance and the aircraft's own Terrain Awareness and Warning System (TAWS/EGPWS) to avoid a controlled flight into terrain (CFIT).
The incident was investigated by the Hong Kong Civil Aviation Department (CAD). It was determined that the aircraft had come within approximately 2,000 feet of the terrain horizontally, though it managed to stay above the peaks vertically due to the expedited climb. The event serves as a stark reminder of the importance of strict adherence to SIDs in mountainous regions and the vital role of ATC radar monitoring in preventing catastrophes.