Accident Summary
On 24 June 1979, at approximately 0945 local time, a Piper PA-38-112 Tomahawk, registration HB-PCP, crashed on the Schwändialp, about 4 km south of Schwarzenberg in the canton of Lucerne, Switzerland. The aircraft was destroyed, and both occupants sustained minor injuries.
Aircraft and Crew Information
The aircraft was owned by Gribair SA of Bern. It had been imported new from the United States in late October 1978 and had accumulated about 88 operating hours by the day of the accident. The pilot, a Swiss citizen born in 1955, held a valid private pilot license. He had logged 97 total flight hours, with 50 hours in the previous 90 days, and 3 hours on the accident type in the last 90 days. The passenger was the pilot’s uncle.
Accident Sequence
The flight departed Beromünster airfield at 0924 local time on a VFR flight to the Schwarzenberg area at the northern foot of Mount Pilatus. The passenger intended to take aerial photographs of his cheese dairy. The pilot had conducted a reconnaissance flight with his sister the previous day. After about 10 minutes, the aircraft reached Schwarzenberg (840 m above sea level) and flew over at low altitude. Continuing south along the Giessbachtälchen valley, the pilot flew at low altitude to allow the passenger to photograph additional properties. As the aircraft entered the narrowing valley, the pilot noticed it was no longer climbing sufficiently and extended the flaps to increase lift. Approximately 1.5 km further, the aircraft crashed from about 20 m height onto swampy alpine ground after the left wing struck a treetop. No fire ensued.
Investigation Findings
The investigation found that the aircraft was airworthy and had no pre-existing defects. Weight and center of gravity were within limits with two occupants and about 75 kg of fuel. According to the flight manual, climb performance at 3300 ft pressure altitude, full power, 15°C, with flaps retracted and 70 KIAS was about 500 ft/min. Stall speeds at full power were 48 KIAS with flaps up and 46 KIAS with flaps down. At the accident site, the flaps were fully extended and locked, the throttle was at full, the mixture rich, and the primer pushed and locked. The carburetor heat setting could not be determined. Weather conditions included 5-7/8 Sc clouds with base around 2000 m, visibility 15 km or more, temperature 15°C, dew point 13°C, and QNH 1013 mbar.
Cause
The investigation determined the cause to be erroneous behavior in hilly terrain and distraction by the passenger.