Flight History
On 24 March 2009, at 13:48 local time, a Piper PA-28-161 Warrior III, registered HB-PPG, departed Grenchen airfield for a training flight under visual flight rules. The aircraft was operated by the Segel- und Motorfluggruppe Grenchen. The crew consisted of a flight instructor and a student pilot; no injuries were reported. After completing four touch-and-go landings, the aircraft proceeded to the Biel area for simulated forced landing exercises. A second exercise was performed near Täuffelen. The crew then flew to Bellechasse airfield for a simulated forced landing onto runway 26. After a normal approach and go-around, approximately 20 to 30 seconds into the climb at about 400 feet above ground level, the engine suddenly lost power. The instructor reported a rough rumbling sound with vibrations, and throttle inputs had no effect. Following standard procedures, the instructor took control. Unable to land straight ahead due to unsuitable terrain and power lines, he attempted a tight left turn back toward the airfield. The aircraft touched down short of runway 08, collided with a fence, and came to a stop about 200 meters north of the airfield after approximately 400 meters of ground roll. The propeller was windmilling until touchdown and the engine stopped automatically.
Weather Conditions
At the time of the accident, meteorological reports from nearby Payerne and Grenchen airfields indicated a temperature of about 5°C and a dew point of -3°C. The wind was from 290° at 12 knots in Grenchen. The general weather pattern featured a cold, moist polar air mass flowing into the Alps, with scattered clouds and possible rain or snow showers. These conditions were conducive to carburetor icing.
Investigation Findings
The Swiss Accident Investigation Board (SAIB) examined the aircraft and the circumstances. During the pre-flight ground check, the carburetor preheat system had produced a 30–50 RPM drop, but functioned normally during the initial flight phases. After the power loss, the engine was unable to restart. Examination revealed that carburetor icing was likely, as the ambient temperature and dew point were within the range for ice formation. Additionally, the carburetor preheat system was found to be in a deficient technical condition, which reduced its effectiveness in preventing ice buildup.
Probable Cause
The accident was due to a collision with obstacles following a forced landing because of an engine power loss. The power loss was likely caused by carburetor icing. The deficient technical condition of the carburetor preheat contributed to the power loss.