What happened
On August 20, 1978, a Piper PA 28 R-200 Arrow, registration HB-OKW, departed Altenrhein for Zurich with two passengers on board. During the initial climb and cruise, the pilot utilized the right fuel tank before switching to the left tank to deplete its contents. While approaching Zurich, the pilot transitioned the fuel selector back to the right tank.
During the approach near Bassersdorf, the engine began to sputter. The pilot increased power, and the engine briefly returned to normal operation. However, while maneuvering to align with runway 28 at Zurich Airport, the engine sputtered again and eventually ceased running entirely. The pilot attempted an emergency landing, but the aircraft struck several obstacles before coming to a halt on the A1 motorway, approximately 650 meters short of the runway threshold. The impact caused two injuries and significant damage to the aircraft and roadside infrastructure.
The investigation
Investigators examined the aircraft's systems and fuel levels following the crash. Upon inspection, the left fuel tank was found to be empty, containing only a few drops of fuel, while the right tank still held approximately 27 liters. The fuel selector was found in the position for the right tank. Despite the engine failure, the engine started immediately during ground testing, and no mechanical defects were found in the engine or aircraft systems. Analysis of the fuel showed that while the vapor pressure was low, it was not a factor in the engine failure at the flight altitude.
Findings
- The engine failure was caused by a disruption in the fuel supply.
- The pilot failed to adequately monitor the fuel system during the approach.
- There was a likely error in the manipulation of the fuel selector, which likely caused the engine to run out of fuel from the left tank before the pilot switched back to the right tank.
Safety action
- The forced landing was mismanaged, leading to the impact with obstacles on the motorway.