What happened
On April 1, 2016, a private Robin HR100-210D, registration HB-EUM, departed Basel-Mulhouse airport for Saint-Dié-des-Vosges. During the initial stages of the flight, the pilot experienced several identification errors from ground controllers, who incorrectly recorded the aircraft registration.
As the flight progressed, the pilot encountered a thickening cloud layer. To avoid flying into the clouds, the pilot climbed to approximately 4,200 ft to fly "on-top" of the cloud layer. However, as the terrain rose toward the Vosges mountains, the pilot descended back below the cloud base to maintain visual contact with the ground. While flying at a low altitude through a valley, the aircraft disappeared from radar at 19:26. The wreckage was later discovered in a wooded area on a hillside, where the impact and subsequent fire destroyed the aircraft. The pilot was killed in the accident.
The investigation
The BEA examined the wreckage, which showed no evidence of mechanical failure prior to impact. The propeller damage indicated that the engine was producing power at the moment of collision. Investigators also reviewed radar tracks, radio communications, and meteorological data.
Witness testimony from a person working in a nearby field indicated that the aircraft was flying very low, following the valley floor just beneath the cloud base. Meteorological analysis confirmed that a weather front was moving through the region, bringing high humidity and low ceilings that were unfavorable for VFR flight. The investigation also noted that the initial error in recording the aircraft's registration by air traffic controllers contributed to delays in identifying the correct aircraft during the search and rescue phase.