Korean Air 8509, Stansted, 22 December 1999

On 22 December 1999, Korean Air Cargo Flight 8509 — a Boeing 747-2B5F, registration HL7451 — rolled into the ground shortly after taking off from London Stansted. All four crew died.

The instrument

The captain’s attitude director indicator was being fed faulty roll information by a failed inertial navigation unit. It showed the aircraft wings level while it was in fact banking steeply left.

Taking off into darkness, with no outside horizon to check against, the captain flew the instrument. The aircraft rolled past 90 degrees and struck the ground.

This is the same trap that destroyed Air India 855 in 1978, in almost exactly the same way: a failed attitude reference, a dark departure with no visual horizon, and a captain flying an instrument that was lying to him.

The repair that did not fix it

The fault had already been reported on the inbound sector.

At Stansted, maintenance staff did not have the correct manual. They tested the ADI itself, saw it respond, and concluded the problem was resolved. But the test button they used checked only the ADI, not the inertial navigation unit feeding it — and the INU was the actual fault.

The aircraft was released with the defect intact.

The flight deck

Two other people knew something was wrong.

The first officer’s own ADI was working correctly and showed the true bank angle. He did not intervene.

The flight engineer repeatedly called out that the instruments disagreed. He was not heeded.

What changed

The AAIB’s recommendations went to crew resource management. It urged Korean Air to update its training and flight quality assurance programmes, and — pointedly — to adapt imported Western CRM training so that it worked within Korean cultural norms rather than against them, because a steep authority gradient on the flight deck had again stopped junior crew from being effective.

That is the same conclusion reached after Korean Air 801 two years earlier. Korean Air subsequently undertook a widely studied safety overhaul, and its record since is entirely different.

Related

• Air India 855 — the same instrument failure
• Korean Air 801
• Tenerife — where CRM came from