What happened
On September 7, 2010, a Boeing 737-400, registration TC-TLE, operated by Tailwind Airline, was performing a regular international flight arriving at Lyon Saint-Exupéry Airport. The crew was conducting a non-precision approach to runway 36R using the localizer, as the glide slope was out of service.
While being radar-guided by air traffic control, the aircraft intercepted the localizer. During the descent, the crew began their final approach descent before reaching the published final approach fix (FAF) for their current altitude. Consequently, the aircraft's descent profile remained below the established theoretical approach path. As the aircraft continued this low profile, the Minimum Safe Altitude Warning (MSAW) system in the control tower was triggered. The air traffic controller issued three commands for a go-around, which the crew executed at 17:10 UTC. There were no fatalities or injuries during the incident.
The investigation
The BEA investigation focused on the flight path and the procedures used during the approach. Investigators examined the aircraft's flight parameters via the Quick Access Recorder (QAR) and analyzed the aeronautical publications in effect at the time. The investigation also reviewed the radar guidance practices used by the air traffic controller and the specific approach charts that featured multiple possible final approach fixes (FAF) depending on controller instructions.
Findings
- The crew failed to correctly identify the appropriate descent fix for the approach.
- The crew maintained an inadequate descent profile during the final approach.
- The publication of approach charts containing multiple FAFs, including one that is only used upon specific controller instruction, contributed to the confusion.
- There was a lack of clear communication to the crew regarding the exact identification of the final approach procedure to be used.
- The use of radar guidance at an altitude lower than the published intermediate segment altitude was a contributing factor.