DAVID FULLBROOK / SINGAPORE AND DAVID LEARMOUNT / LONDON
Pilots thought to have mishandled aircraft after misunderstanding height clearance
Chinese accident investigators say the cause of a fatal Korean Air (KAL) Boeing MD-11 Freighter crash at Shanghai in April 1999 was a misunderstanding over air traffic control (ATC) instructions. The main factor appears to have been crew confusion because ATC gave the altitude clearance in metres, which are standard in China, whereas Korean aviators are more familiar with feet.
South Korea's Ministry of Construction and Transportation has revealed the findings of the crash probe while announcing a proposed ban on KAL's freight operation to Shanghai for two years.
The ministry's Aviation Safety division says Chinese crash investigators, with assistance from US and Korean teams, determined the probable cause was "the flight crew's loss of altitude situational awareness". They "overreacted with abrupt flight control inputs" while trying to comply with height clearances during a standard instrument departure from Shanghai.
ATC had initially cleared the aircraft to "climb to 1,000m" (3,000ft). But as the aircraft was identified on radar approaching that altitude, it was cleared to 1,500m. When ATC saw the aircraft passing through 1,400m they extended the clearance to 5,700m. The crew did not reply.
The ministry believes that the KAL pilots had begun to argue about whether the "1,500m" clearance was for 1,500ft. The fact that they had become confused about something was clear from a brief conversation recovered from the damaged cockpit voice recorder, and the fact they had put the aircraft into a steep dive. It hit the ground 2min after take off with wings level in a 45° nose-down attitude.
KAL disagrees with the findings, saying they are based on a snippet of conversation from the aircraft's voice recorder.
Investigators had little else to go on as the flight data recorder was almost totally destroyed when the aircraft ploughed into a construction site about 10km south of Shanghai's Hongqiao Airport. Five people on the ground and all three crew on board were killed.
Source: Flight International
