Nighttime Terrain Collision Near Clermont-Ferrand (F-BMCH)

Flight and Crash Circumstances During a night flight from Lyon to Clermont-Ferrand, the crew received a briefing regarding adverse weather conditions, including storm activity, turbulence, heavy rain, icing, and low ceilings. The aircraft was cleared to begin an ILS approach to Clermont-Ferrand and authorized to descend to 3,600 feet. While in clouds, the four-engine aircraft struck trees and crashed inverted on the Pic du Picot, a 1,100-meter peak in the Forez Mountain Range near Noirétable. The wreckage was located seven hours later in the Faye forest. Eight passengers were evacuated, while 60 other occupants were killed. ## Official Investigation Findings The investigating committee determined that the accident was the direct result of a collision with terrain at night in stormy conditions near a cold front. The aircraft was following what appeared to be a normal approach procedure but had deviated approximately 30 kilometers to the east. The committee identified two primary anomalies. First, the crew believed they were directly over Clermont-Ferrand, although the beacon was more than 30 kilometers away. This was attributed to a significant rotation of the radiocompass that the crew did not detect. Second, the crew announced they were over the beacon more than three minutes earlier than the estimated eight-minute interval. This discrepancy may have been overlooked due to reliance on the radiocompass, a failure to check the time, a reading error, or distraction from difficult steering in turbulence and the presence of an instructor. The committee ruled out a pirate transmitter. The erroneous radiocompass indication likely resulted from a fault in the on-board antenna system under certain electric field conditions, or more likely from very localized precipitation accompanying the cold front that acted as a transmitter of micro-discharges, overpowering the Clermont-Ferrand beacon signal. The interception of the ILS alignment plan and the possible visibility of the luminous halo of the city of Thiers may have reinforced the crew's mistaken position. Although the instructor pilot was known for emphasizing cross-checking positions, such as using the radial of Moulins, the crew did not perform these checks. The committee concluded that the accident was a consequence of a controlled flight into terrain.