Investigation Summary
The flight was cleared for a VOR/DME approach to runway 11, a procedure requiring the aircraft to maintain 2,100 feet until reaching the Final Approach Fix (FAF) at 6 miles DME. However, the flight crew began their final descent prematurely at 6.8 miles DME. Throughout the descent, the crew failed to conduct a verbal approach briefing and did not make the required callout when passing 1,000 feet. The investigation highlighted that the aircraft was not equipped with an Enhanced Ground Proximity Warning System (EGPWS), which would have provided a 'Caution Terrain' alert 32 seconds before impact. Additionally, the airport's Minimum Safe Altitude Warning (MSAW) system did not cover the approach path for runway 11, leaving the controllers unable to warn the crew of their dangerously low altitude.
Final Conclusions
The BEA Tunisia concluded the accident was a Controlled Flight Into Terrain (CFIT) caused by the crew's failure to properly execute and control the final approach, specifically by failing to respect the approach fix altitudes. Contributing factors included adverse weather with reduced visibility, shortcomings in the pilots' training regarding conventional VOR/DME approaches, and the crew's relatively low experience levels on the Boeing 737-500 type.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
VOR/DME Approach
A non-precision approach using a Very High Frequency Omnidirectional Range station and Distance Measuring Equipment to determine position and distance from the airport.
EGPWS
An Enhanced Ground Proximity Warning System that uses GPS and a terrain database to provide alerts; this aircraft lacked the system, which could have provided a 32-second warning.
MSAW
Minimum Safe Altitude Warning is a ground-based safety tool for air traffic controllers that alerts them if an aircraft is too low; the Tunis system did not cover the specific approach path used.
Interesting Facts
- 01The aircraft broke into two halves upon impact, with a fire breaking out in the rear section.
- 02The weather at the time included fog, rain, and blowing sand, creating Instrument Meteorological Conditions (IMC).
- 03The Minimum Safe Altitude Warning (MSAW) system at the airport did not cover the runway 11 approach.
- 04The aircraft was not equipped with an Enhanced Ground Proximity Warning System (EGPWS).
- 05The investigation found the crew did not conduct a verbal approach briefing during the descent.
Safety Actions & Advisories
MSAW Coverage Review
The investigation recommended studying ways to improve the volume of sky covered by the Minimum Safe Altitude Warning device at Tunis-Carthage to include all runway approaches.