Accident
On Saturday, 11 March 1978, at 1301 local time, a Piper Arrow PA-28 R 200 (registration HB-PAH) crashed during a forced landing on a snow-covered slope near Evolène in the canton of Valais, Switzerland. The aircraft was destroyed, and the four occupants sustained injuries: one passenger suffered a spinal injury, and the other three were lightly injured.
Flight Details
The pilot, a private pilot born in 1945, departed Sion Airport at 1250 hours with three passengers for a private alpine flight. The planned route was through the Val d'Hérens, Val des Dix, and over several peaks before descending via Saas or Tourtemagne. Earlier that morning, the pilot had completed four check flights totaling 34 minutes with an instructor. The pilot had 352 total flight hours, including 69 hours on the Arrow type.
Engine Failure and Landing
About 10 minutes after departure, while climbing near the Merdesson valley at an altitude of approximately 2400 m (about 8000 ft), the engine suddenly lost power. The pilot attempted to troubleshoot by adjusting throttle and other controls but did not activate the electric fuel pump or adjust the mixture. As the aircraft descended into the valley, the pilot determined that a return to the Rhône valley or an approach to Evolène was not feasible. He decided to execute a forced landing using mountain landing techniques on a north-facing snowy slope with an incline of about 30 degrees. The landing resulted in severe damage: the nose wheel leg bent backward, the main landing gear broke, and the left wheel was torn off. The propeller, rotating due to relative wind, was not damaged.
Investigation Findings
- The pilot held a valid private pilot license and had good experience on the type. No evidence indicated any health issues at the time of the accident.
- The aircraft, built in 1975, had a valid airworthiness certificate and was properly maintained. Its weight was 88 kg below the maximum limit, and center of gravity was within limits.
- Engine: Lycoming IO-360-C1C of 200 hp. The mixture control was found in the LEAN position, which the pilot stated he set after landing.
- Weather at the time: excellent visibility, light to moderate winds, temperature +4°C, humidity 40-45%, with 1/8 altocumulus and some cirrus. No icing was likely.
- Fuel analysis of a sample from the tanks (about 140 liters removed) met specifications for 100 LL aviation gasoline.
- The engine was removed and bench-tested: it started immediately, ran normally with normal compression. Complete disassembly revealed no faults.
- The electrical fuel pump was not used, and the pilot did not attempt to adjust the mixture during the failure.
- The Emergency Locator Transmitter (ELT) activated but was not heard due to the aircraft's location. VHF calls for help were unsuccessful.
- An analysis indicated that the climb rate from Sion to the accident site was about 600 ft/min, likely aided by upslope winds. After power loss, the descent rate was approximately 5 m/s, giving the pilot less than one minute to react.
The accident occurred in an area unsuitable for forced landings. The pilot's decision to land on the snowy slope was considered the best option given the circumstances.
Cause
The accident was due to an engine power loss occurring over terrain unsuitable for a forced landing. The cause of the power loss could not be determined.