Incident Overview
On August 20, 1978, a Piper PA 28 R-200 "Arrow" with registration HB-OKW departed Altenrhein airfield at 10:08 local time. The aircraft was operated by a private pilot carrying two passengers for a VFR flight to Zurich. The purpose of the trip was to have the aircraft's VHF radio repaired before continuing to Salzburg.
Flight Progression and Fuel Management
At takeoff, the right fuel tank contained 38 liters of AVGAS 100 LL, while the left tank held approximately 15 liters. The pilot initially selected the right tank for the climb and cruise phase. Over Arbon, the selector was switched to the left tank to deplete its contents. During the approach checks near Winterthur, the pilot stated he switched back to the right tank, believing it to be fuller. However, post-accident analysis suggests the selector may have remained on or inadvertently moved to the empty left tank.
Engine Failure and Crash Sequence
While in the vicinity of Bassersdorf, northwest of Kloten, the engine began to sputter. The pilot reported that full throttle temporarily restored normal operation. At 10:35, after being cleared to land on Runway 28, the engine failed completely during the turn to final approach. The aircraft struck several obstacles, including a wildlife fence and lighting mast, before coming to rest on the N1b motorway, approximately 650 meters from the runway threshold.
Investigation Findings
The investigation determined that no mechanical defects existed in the engine or fuel systems; bench tests showed the engine started immediately and ran normally. The left tank was found empty, while the right tank still contained 27 liters of fuel. The fuel selector valve was found in the "Right Tank" position after the crash. Tests indicated that switching from an empty tank to a full one takes approximately 20 seconds for fuel flow to resume. The probable cause was identified as fuel exhaustion due to insufficient control of fuel supply and a likely error in manipulating the fuel selector valve.