What happened
On a scheduled service from Taipei to Hong Kong, a Thai Airways International Boeing 747 (implied by context of large passenger service) was conducting an instrument approach to runway 31 under conditions of heavy rain and significantly reduced visibility. The flight crew, consisting of a captain, a co-pilot flying manually from the right seat, and a third pilot acting as system operator, was cleared for an ILSB approach. While the aircraft initially remained within the safety parameters of the localizer and glide slope, the crew began making series of corrective turns in response to radar advisories.
As the aircraft approached the 1-mile marker, heavy rainfall caused interference with the precision approach radar. During this period, the aircraft drifted left of the centerline, prompting the captain to instruct the co-pilot to move back to the right. Shortly thereafter, the captain observed the sea surface through the side window at an altitude of approximately 100 feet. Despite an immediate attempt to climb, the aircraft struck the water roughly 3,925 feet before the ILS reference point. The impact caused the starboard wing and landing gear to detach, tearing the fuselage and leading to a rapid sinking.
The accident resulted in 24 fatalities, including passengers who drowned inside the cabin or were lost at sea, while others were rescued by nearby vessels and helicopters.
Findings
Investigations into the crash identified several critical failures in flight management. The crew failed to follow established company procedures for a 'Captain monitored' approach during periods of low visibility. Specifically, the captain did not provide adequate oversight of the manual flight path being executed by the co-pilot. Furthermore, the co-pilot mishandled the aircraft's controls following a descent below the minimum altitude, an error that may have been exacerbated by localized downdrafts.