What happened
On the evening of January 16, 2006, an EADS SOCATA TB20 GT (registration N250AG) departed from Chambéry Aix Les Bains under IFR conditions. The flight was a private mission involving the pilot and three passengers. Shortly after takeoff from runway 36, the aircraft struck a mountain at an altitude of 2,100 feet, approximately 2.7 NM northwest of the aerodrome. The impact caused a post-crash fire that destroyed most of the airframe. All four fatalities occurred during the collision.
The investigation
The investigation focused on the flight path and the pilot' and the navigation setup during the initial climb. Investigators examined the aircraft's instrumentation, specifically the Horizontal Situation Indicator (HSI), and the published departure procedures (SID DANBO 2C). The investigation established that the engine was delivering power at the moment of impact and that the aircraft was within its authorized weight and balance limits.
Analysis of the navigation charts revealed a potential for confusion: the Jeppesen documentation for the departure procedure mentioned a magnetic course of 357° but did not explicitly state the orientation of the ILS localizer axis (177°). Furthermore, the investigation noted that the pilot was performing a specific maneuver—realigning with the localizer from a rearward position—which is a rare procedure in France and requires specific familiarity.
Findings
- The pilot likely made an incorrect HSI display setting while attempting to intercept the localizer axis during the DANBO 2C departure procedure.
- This error caused the pilot to interpret the HSI needle as anti-directional, leading to a left-hand correction that actually increased the deviation from the intended track.
- The aircraft drifted approximately 30 degrees left of the planned course before the collision.
- Reduced visibility due to snowfall and the lack of radar coverage below 2,800 feet prevented air traffic controllers from detecting the deviation.
- The passengers, while licensed pilots, did not hold instrument ratings and were unlikely to have identified the navigational error.