KOREAN AIR FLIGHT 801 CRASH: A CASE STUDY

1
KOREAN AIR FLIGHT 801 CRASH A CASE STUDY

• Vidyadhar Rangojoo

2
On August 6, 1997 142 AM.

• Korean Airlines Flight 801 crashed into terrain
  on approach to Won Pat Intl airport, Guam. The
  impact site lies at 658ft on Nimitz Hill.
• Death toll 237. Survivals 28.
• Classified as a Controlled-flight-into-terrain
  (CFIT) accident.

3
Wreckage of Flight 801
Ariel view of the location of crash
Crash site
4
Wreckage of Flight 801CONTD
KAL 801 after the crash
Ariel view
5
Reasons for the crash

• Complex combination of events
• Glide slope not operational.
• Pilot error.
• Inhibition of Minimum Safe Altitude Warning
• System
• Ground based controller.
• Alerts controllers visually/aurally when tracked
  flight descend below a predetermined min safe
  altitude.

• The horizontal needle represents the glideslope.

The horizontal needle represents the glide slope.
6
MSAW Alert
7
MSAW General Monitoring
Minimum Safe Altitude (MSA)
Terrain Clearance Altitude
8
MSAW System Overview

• 1990 System configured to monitor area within
  55-nm radius of the Guam radar.
• 1993 New system installed citing frequent
  nuisance warnings issued by system.
• This change reduced MSAW processing to a 1-nm
  ring b/w 54-nm and 55-nm from radar facility.
• New MSAW software installed at Guam to update
  terrain database includes the inhibition zone.
• Facility Inspection of this software failed to
  note MSAW inhibition entirely.

9
The Guam MSAW Inhibition zone
MSAW Service Area Boundary (55 nm)
Inhibit Zone (54 nm)
Guam
Pacific Ocean
10
Analysis

• The glideslope for runway 6L was out of service,
  captain lost awareness of flights position on
  final approach.
• Altitude callouts by onboard GPWS ignored by
  flight crew mistaken for nuisance messages over
  Guam.
• Poor illumination surrounding Nimitz Hill.

11
Effectiveness of MSAW.

• NTSB/FAA simulation indicated that, without the
  inhibition, MSAW would have generated an alert 64
  seconds before impact.
• NTSB This would have been sufficient for the
  controller to advise KA 801.
• NTSB concluded that FAAs quality assurance of
  MSAW was inadequate.

12
Lessons learnt.

• Configuration management.
• Human error.

13
Related Incidents

• Dulles International Airport,1994.
• Houston Intercontinental Airport,1998.

14
References..

• Paper titled What should aviation safety
  incidents teach us? by John C. Knight.
• Paper titled Framing analysis of software
  failure with safety cases .William S. Greenwell,
  John C. Knight .
• http//www.cnn.com/WORLD/9708/10/guam.crash/
• http//ns.gov.gu/guam/indexmain.html

15
QUESTIONS???