KOREAN AIR FLIGHT 801 CRASH: A CASE STUDY

1
KOREAN AIR FLIGHT 801 CRASH A CASE STUDY

• Vidyadhar Rangojoo

2
The Incident.

• Korean Airlines Flight 801 crashes 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
4
Wreckage of Flight 801
The Crash site
5
Wreckage of Flight 801CONTD
KAL 801 after the crash
6
Wreckage of Flight 801
Ariel view
7
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.

8
Reasons for the crash (CONTD)

• FAA changed a safety critical system without
  reexamining the scenario the system addressed.
• FAA allowed Guam to operate normally despite
  having two safety-critical systems out of
  service.

9
MSAW General Monitoring
Minimum Safe Altitude (MSA)
Terrain Clearance Altitude
10
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 and 55nm 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.

11
The Guam MSAW Inhibition zone
MSAW Service Area Boundary (55 nm)
Inhibit Zone (54 nm)
Guam
Pacific Ocean
12
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 bye
  flight crew mistaken for nuisance messages over
  Guam.
• Poor illumination surrounding Nimitz Hill.

13
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.

14
Lessons learnt.

• Configuration management.
• Human error.

15
Related Incidents

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

16
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