What happened
On the evening of September 28, 1974, a Cessna 182 G, registration HB-CTB, departed Bex for Lausanne under challenging meteorological conditions. The flight, conducted at dusk with a low cloud ceiling and rain, carried the pilot and three passengers. Shortly after takeoff, the aircraft began experiencing engine irregularities.
As the aircraft progressed toward Lausanne, witnesses observed the plane flying at extremely low altitudes, sometimes as low as 30 to 50 meters above the ground or lake. While the engine initially provided enough power to maintain altitude near Vevey, the engine eventually failed completely as the aircraft approached the Lausanne suburbs. In an attempt to maneuver, the pilot executed a sharp left turn at a very low altitude, which induced an aerodynamic stall. The aircraft subsequently struck a television antenna and a telephone pole before crashing into a garden in the Pully area. The impact was severe, resulting in two fatalities (the pilot and one passenger) and two serious injuries to the remaining occupants. The aircraft was destroyed.
The investigation
Investigators examined the wreckage and the aircraft's maintenance history, finding that the engine and airframe were well-maintained and within weight and balance limits. The investigation focused on the cause of the engine failure and the pilot's decision-making during the emergency.
Technical analysis of the fuel system revealed that the fuel filter contained water and impurities. While no mechanical defects were found in the engine itself, the presence of contaminants suggested that the engine's performance was compromised by poor fuel quality. Furthermore, the investigation noted that the pilot had not updated his flight log for the day's operations and had departed without notifying the airfield office at Bex.
Findings
- The primary cause of the accident was an aerodynamic stall during a steep turn at low altitude following an engine failure.
- The engine failure was likely caused by fuel exhaustion or the ingestion of water and impurities into the carburetor, as evidenced by the contaminated fuel filter.
- Adverse weather conditions, including heavy rain, low visibility, and a low cloud ceiling, prevented the pilot from following standard approach procedures and restricted his ability to maintain sufficient altitude.
- The pilot's decision to fly over densely populated areas while attempting to reach Lausanne increased the risk during the engine malfunction.