What happened
On June 21, 1983, a Piper Cherokee Six PA-32-300, registered as D-EHEM, departed Le Castellet in southern France on a private VFR flight bound for Strasbourg and Mannheim. The aircraft carried two pilots and one passenger. After departing, the crew navigated along the southern foothills of the Jura mountains toward Basel.
During the climb to 9,000 feet under CVFR guidance from Zurich Control, the engine experienced brief stuttering near Neuchâtel at approximately 4,500 feet. The crew activated the electric auxiliary fuel pump and switched tanks, which resolved the issue temporarily. Believing the problem was isolated to a specific tank selection, they continued the flight.
As the aircraft approached Basel, weather conditions deteriorated, prompting the crew to descend below the cloud base along the Rhine River. At approximately 2,500 feet above ground level, the engine began stuttering again. Despite activating the electric pump and switching between main tanks, the power loss persisted. With altitude rapidly depleting, the pilots initiated an emergency landing on a grassy field situated between a railway line and an autobahn near Eiken.
The touchdown occurred at the end of the usable runway area with flaps still retracted and speed relatively high. The aircraft rolled out for approximately 116 meters before striking a tree with its left wing, shearing it off. It then slid down a slope, coming to rest 170 meters from the initial impact point. All three occupants sustained serious injuries.
The investigation
The Swiss Transportation Safety Investigation Board (STSB) examined the wreckage and conducted tests on the fuel system components. A critical finding was that the mechanically driven fuel pump exhibited severe wear with a significant leak at the drive-side seal, indicating it had reached the end of its service life without prior detection.
Tests confirmed the ignition system and exhaust were functional. The investigation also reviewed maintenance logs, noting a previous similar incident two months earlier where intermittent stuttering occurred but resolved after cleaning filters and nozzles. The crew's decision to continue flying was influenced by this prior experience, leading them to believe the issue was minor fuel contamination rather than mechanical failure.
Findings
The primary cause of the accident was a failed emergency landing following an engine power loss due to intermittent interruptions in the fuel supply. The technical investigation identified a severely worn mechanical fuel pump as a likely contributing factor, which could no longer guarantee consistent fuel flow. Other potential causes considered but not confirmed included fuel contamination or carburetor icing, though the latter was deemed less likely given the resolution of previous symptoms via tank switching.
Safety action
The report highlighted the necessity of reviewing prescribed overhaul intervals for mechanically driven fuel pumps to prevent undetected wear from leading to in-flight failures.