Accident Overview
On 17 August 1987 at 1440 local time, a Piper PA-28-236 (registration HB-PEZ) experienced an engine failure shortly after takeoff from Fribourg-Ecuvillens airfield. The aircraft was being operated by the Section vaudoise de l'AéCS and was engaged in a private pleasure flight. The pilot, a Swiss citizen born in 1943, held a valid private pilot license and had accumulated 323 total flight hours, including 46 hours on the accident type in the preceding 90 days. One passenger was on board.
Flight History
The flight originated at Lausanne airfield earlier that day, around 1230 local time. The pilot had filled one fuel tank prior to departure. After a flight over the Alps with a stop at Ecuvillens, the pilot conducted pre-flight checks using only the electric fuel gauges, which he considered pessimistic based on experience. After a stop of over an hour, the pilot prepared for the return flight to Lausanne. At 1430, the aircraft departed from runway 28.
Shortly after takeoff, while initiating a left turn, the engine lost power and experienced misfiring. The pilot reactivated the electric fuel pump and turned back toward the airfield, announcing the emergency via radio and intending to land on runway 10, opposite the departure direction. The aircraft touched down at a heading of approximately 130 degrees, 30 degrees off the runway centerline, with the nose gear collapsing first. The aircraft came to rest on the grass between the taxiway and the runway.
Investigation Findings
Post-accident examination revealed that the right fuel tank contained 25 US gallons (approximately 95 liters), while the left tank held about 1.1 US gallons (4 liters). The fuel selector was positioned to the left tank. The aircraft's flight manual specified a total fuel capacity of 77 US gallons (291 liters) with 72 US gallons (273 liters) usable. A difference of about 20 liters is not accessible to the engine in all flight attitudes.
Weather conditions were excellent with 6/8 cloud cover, wind from 200 degrees at 4 knots, and visibility between 20 and 50 kilometers. The pilot held a valid license, and the aircraft had valid airworthiness and registration certificates.
Analysis
The engine power loss resulted from fuel starvation caused by the fuel selector being on the left tank, which was nearly empty at the time of takeoff. A fuel reserve of less than 10 liters does not guarantee reliable engine operation in all flight attitudes. The pilot likely made an error during pre-flight checks, possibly due to the design of the fuel selector, which was mounted vertically on the left fuselage wall, outside the pilot's normal field of view, making the selected position unclear. Electric fuel gauges provide imprecise readings, and the aircraft's parking position on a slope may have shown an optimistic reading, failing to alert the pilot to the low fuel level in the left tank. A visual check through the filler opening would have revealed the actual fuel quantity.
The low altitude at the time of the failure left little time for corrective actions. Engaging the electric fuel pump was a reasonable first step, but the selector's location hindered easy verification or switching. The pilot's decision to return to the airfield was understandable given the unfavorable terrain below. The approach conditions—low altitude turn, reduced speed, and pilot stress—likely contributed to the missed landing.