What happened
On April 16, 1979, a Piper PA-34-200, registration HB-LEP, was conducting a visual flight rules (VFR) flight from Cannes to Basel. After a stop in Marseille, the pilot received weather advice suggesting a route via Lyon and the Jura mountains to avoid thunderstorms and precipitation. Following the departure from Marseille at 16:40, the aircraft encountered deteriorating weather conditions north of Lyon.
As the flight progressed through the Mâcon region, the pilot performed several significant course changes to avoid convective activity. During this period, the pilot began flying partially by instruments, a technique for which they had limited training. This led to a complete loss of geographical orientation. The pilot attempted to use various navigation aids, including the Dôle NDB and several VOR stations, but was unable to identify their position.
While the pilot managed to contact Basel Tower to request assistance and a transponder code, they were unable to establish communication with Zürich Information as instructed due to incorrect radio frequency settings. After flying toward the Payerne area and circling, the pilot spotted a lit factory and decided to perform an emergency landing in a field near Dompierre, France. The aircraft was destroyed upon impact, but all four occupants survived without injury.
The investigation
SUST examined the flight preparations and the pilot's technical proficiency. The investigation established that the pilot had undergone a very brief transition training of only 5 hours and 35 minutes on the Piper PA-34-200 type, which was insufficient for full familiarity with the aircraft's systems.
Furthermore, the investigation found that flight preparations in Marseille were inadequate. The pilot did not create a new navigation plan, did not calculate fuel consumption for the revised route, and failed to update the charts. Additionally, the aircraft was not refueled in Marseille despite the pilot's knowledge of the worsening weather. The investigation also noted that the pilot's radio settings prevented the requested contact with Zürich Information, as the transmitter was only active on the emergency frequency (121.5 MHz).
Findings
- The pilot lost orientation because they continued a VFR flight under conditions that required instrument flight techniques.
- Inadequate flight preparation contributed to the loss of situational awareness.
- Minimal transition training and low experience with this specific aircraft model hindered the pilot's ability to manage the emergency.
- The pilot's failure to update navigation charts and fuel calculations left them unprepared for the increased complexity of the weather-avoidance maneuvers.