Korean Air 801, Guam, 6 August 1997
229 of 254 aboard died when a 747-300 struck Nimitz Hill on approach to Guam. The glideslope was out of service and the terrain warning had been modified.
On 6 August 1997, Korean Air Flight 801 struck high ground on Nimitz Hill while approaching Guam. 229 of the 254 people aboard died; 25 survived.
The aircraft was HL7468, a Boeing 747-3B5.
What happened
The glideslope for runway 6L — the part of an ILS that gives vertical guidance — was out of service. That turned an ordinary precision approach into a non-precision approach, which is flown by stepping down through published altitudes rather than following a beam.
The NTSB found that the captain failed to adequately brief and execute that non-precision approach, and that crew communication broke down as the aircraft descended. Captain fatigue and shortcomings in Korean Air’s training were contributing factors. The captain appears to have believed the glideslope was working and followed a spurious signal.
Two things that might have caught the error did not:
- The crew’s own cross-checking of altitude against distance, which is the whole discipline a non-precision approach demands.
- The Minimum Safe Altitude Warning system on the ground, which had been deliberately modified to reduce nuisance alarms and no longer covered the area where the aircraft descended into terrain.
Why it is instructive
This is a textbook controlled flight into terrain accident: nothing was wrong with the aeroplane. It was flying normally, under control, right up to the impact.
The pattern behind it — a precision approach downgraded to a non-precision one, at night, into unfamiliar terrain, with a tired crew and a steep authority gradient on the flight deck — is precisely what crew resource management was invented to break, and it showed that CRM had not yet taken hold everywhere.
Terrain awareness technology moved on sharply afterwards. Enhanced Ground Proximity Warning Systems, which compare position against a terrain database rather than only looking down, became standard and have made this category of accident far rarer.
What changed on the ground
The accident also exposed how badly airlines could handle the aftermath. The Foreign Air Carrier Family Support Act of 1997 followed directly, requiring international carriers serving the United States to file family-assistance plans meeting the same standards as domestic airlines.
Korean Air suspended its Guam service for more than four years.
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Pan Am 103, Lockerbie, 21 December 1988
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El Al 1862, Amsterdam, 4 October 1992
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