What happened
On October 14, 2007, a Reims Aviation F 172 M, registration F-GAGT, was conducting a flight from Bagnères to Auch. The flight was a passenger trip carrying the pilot and three passengers, including two children. Following the visual approach instructions, the pilot intended to follow the right flank of the Luchon valley heading north, eventually turning right and then left near the village of Cierp.
During the flight, a witness observed the aircraft climbing and turning right over the village of Gouaux-de-Luchon. The aircraft was then seen flying at a low altitude, following the north flank of a secondary valley that runs perpendicular to the main valley. Shortly thereafter, the aircraft struck heavily forested, steep terrain at an altitude of approximately 4,430 feet. The impact resulted in four serious injuries and the total destruction of the aircraft.
The investigation
The investigation examined the aircraft's wreckage, flight logs, and witness testimonies. Analysis of the wreckage and the flight path confirmed that the engine was functioning normally at the time of the accident and that the aircraft was flying at a relatively low speed upon impact. The flaps were found to be retracted.
The investigation also scrutinized the pilot's flight preparation. The pilot had prepared the return leg by simply reversing the distances and estimated times from his outbound navigation log. This method resulted in a significant error in the planned course; the pilot recorded a heading of 35 degrees, whereas the actual orientation of the valley was 10 degrees. Furthermore, the pilot failed to utilize visual landmarks, such as the railway line, to navigate the valley exit.
Findings
The primary cause of the accident was the insufficient consideration of terrain characteristics during the preparation of the return flight. The pilot's reliance on reversed outbound data led to a navigation error that placed the aircraft in a narrow secondary valley. Upon entering this valley, the pilot was unable to see the pass located to his left, and the aircraft's altitude was approximately 1,000 feet below the summit of that pass. By the time the pass became visible, the valley had narrowed to roughly 150 meters, making a turnaround impossible due to the aircraft's performance limitations.
Contributing factors included the pilot's lack of mountain flying training and a lack of familiarity with the specific terrain. The investigation also noted that in mountainous environments, the loss of a natural horizon can lead to spatial disorientation, potentially causing excessive bank angles or even a stall, though it could not be definitively determined if this occurred in this instance.