Incident Overview
On April 11, 2018, at approximately 23:52 JST, a Boeing 747-400 registered HS-TGX, operating as Thai Airways International Public Co., Ltd. scheduled flight 660 from Suvarnabhumi International Airport to Tokyo International Airport, executed an emergency go-around to avoid impact with the ground. The aircraft was on approach to Runway 16L at Tokyo International Airport when the event occurred. Following the go-around, the flight crew requested and received clearance for an approach to Runway 22, landing safely at around 00:04 on April 12. There were 384 persons on board, including the pilot in command, 18 other crew members, and 365 passengers. No injuries were reported, and the aircraft sustained no damage.
Flight History
The flight departed Suvarnabhumi International Airport at 18:44 JST with the autopilot engaged. At 23:31, the aircraft contacted Tokyo Approach, receiving information that landing was expected on Runway 16L via a VOR A approach. The aircraft was instructed to descend to 4,000 ft via the DARKS arrival. At 23:45, the crew was cleared for the VOR A approach. Passing over DARKS at 23:47, the landing gear was lowered, and flaps were set to 30. At 23:49, the aircraft was handed off to Tokyo Tower, which cleared it to land on Runway 16L.
Beginning at 23:49:56, the aircraft commenced a circling approach, entering a downwind leg approximately 3.6 nm wide. Descent began at 23:50:12 from 1,100 ft. During the base turn, at 23:51:24, Tokyo Tower advised the crew that their altitude was too low and asked if they had the runway in sight. The crew responded negatively. At 23:51:35, the Enhanced Ground Proximity Warning System (EGPWS) issued a "TOO LOW TERRAIN" caution at an altitude of 304 ft. The crew initiated a go-around at 23:51:38, with the lowest recorded altitude reaching 282 ft.
Probable Causes
The Japan Transport Safety Board determined that the serious incident likely occurred because the aircraft was maneuvered to avoid a ground impact after coming close to the ground surface during the approach. This proximity to the ground was caused by the pilot in command concentrating on modifying the lateral flight path and continuing the descent without adequately monitoring the descent path, while the first officer was focused on monitoring the lateral flight path and did not notice the excessively low descent path.
Investigation Details
The investigation was conducted by the Japan Transport Safety Board under Japanese law and Annex 13 to the Convention on International Civil Aviation. An accredited representative from Thailand participated as the state of operator and registry. Data from the Quick Access Recorder, EGPWS, air traffic control communications, and flight crew statements were analyzed.