What happened
On 16 April 2009, a Boeing 747-400F cargo aircraft, registration B2440, operated by Jade Cargo International Company Ltd., experienced a runway excursion during its landing roll at Incheon International Airport. The aircraft, which had arrived from Frankfurt, landed normally on runway 33R.
Following touchdown, the captain attempted to deploy the reverse thrust systems. While the reverse thrust for engines 1, 2, and 3 functioned as intended, the reverse thrust for the number 4 engine failed to engage. During this process, the forward thrust lever for the number 4 engine moved from the closed position to an intermediate position, and subsequently surged to the maximum thrust position. This sudden increase in power created a severe asymmetric thrust condition, causing the aircraft to veer sharply to the left. Despite attempts by the crew to regain directional control using brakes and right rudder, the aircraft exited the runway, striking a distance marker sign and a runway edge light before coming to a stop in the grass approximately 2,170 meters from the runway threshold. There were no injuries to the four crew members on board, though the aircraft sustained minor damage to the engines and tires.
The investigation
The ARAIB investigation focused on the mechanical behavior of the thrust levers and the flight crew's performance. Investigators examined the autothrottle system, the central maintenance computer, and the flight data and cockpit voice recorders. The investigation confirmed that the thrust levers were functioning normally during pre-flight inspections and that no faults were recorded in the autothrottle or central maintenance computers.
Technical analysis revealed that the number 4 reverse thrust lever could not be raised because the corresponding forward thrust lever was not in the fully closed position. The investigation also noted that the captain continued to use reverse thrust on engines 1, 2, and 3 even after the aircraft had left the runway, which exacerbated the turning motion. The crew's performance was evaluated, specifically regarding situational awareness and the monitoring of engine thrust settings during the landing roll.
Findings
- The primary cause of the excursion was the unrecognized movement of the number 4 engine's forward thrust lever from the closed position to the maximum thrust position, which generated significant asymmetric thrust.
- The captain experienced a temporary loss of situational awareness, failing to recognize the thrust lever movement or the failure of the number 4 reverser.
- The captain failed to immediately terminate the use of reverse thrust on the remaining engines once the aircraft began to veer off the runway.
- The first officer did not adequately monitor the operational status of the thrust reversers during the landing roll.
- The number 4 reverse thrust lever was prevented from operating because the forward thrust lever was not properly retarded to the closed position.