What happened
On February 16, 1961, a Piper J 3 C, registration HB-OCW, was engaged in a recreational flight from Grenchen to Sisseln. After a brief stop in Grenchen, the pilot departed at 16:38 UTC. While navigating the Aare valley toward Solothurn, the pilot encountered thick fog obscuring the Rhine valley.
In an attempt to find better conditions, the pilot altered course toward the north to reach the Rhine, but visibility continued to deteriorate as the aircraft approached Arlesheim. Believing that the destination of Sisslan was unreachable due to the worsening weather, the pilot attempted to divert to the Basel-Mulhouse Airport. However, the airport was also obscured by fog, and after several unsuccessful circuits, the pilot decided to perform an emergency landing in a field near Attenschwiller, France.
During the landing maneuver on the uneven terrain, the aircraft's right wing struck a row of fruit trees. The impact was severe enough to cause the aircraft to pivot 180 degrees. The pilot emerged from the wreckage without injury, but the aircraft suffered significant structural damage.
The investigation
The investigation examined the rapid deterioration of meteorological conditions in the Basel region. Records indicated that visibility dropped from 3 km to as low as 300 meters within an hour. Investigators also reviewed the pilot's flight path and the decision-making process regarding the diversion to Basel-Mulhouse. The investigation noted that while the pilot's intended destination, Sisseln, remained clear of fog for a longer period, the pilot's decision to fly north toward the Rhine led the aircraft directly into the heart of the fog bank.
Findings
- The primary cause of the accident was a rapidly decreasing visibility that forced an unplanned emergency landing.
- The pilot's decision to fly north to rejoin the Rhine placed the aircraft in a region where the fog was most intense.
- The lack of visibility during the field landing likely prevented the pilot from identifying the tree line in time to avoid the collision.
- The aircraft sustained heavy damage, including a broken main spar and torn fabric on the right wing.