Summary
The Swiss Bureau for Aircraft Accident Investigation (BFU) concluded its investigation into the accident of the FFA AS202/15-1 Bravo, registration HB-HFI, which occurred on 17 April 2007 near Ampferenboden, approximately 14 km southwest of Appenzell in the municipality of Urnäsch, Appenzell Ausserrhoden. The aircraft was engaged in a flight with a pilot and a flight instructor on board.
Aircraft Information
The aircraft involved was an FFA AS202/15-1 Bravo, a single-engine training aircraft. The registration was HB-HFI. The aircraft was equipped with cockpit instruments including an artificial horizon, airspeed indicator, variometer, accelerometer, hour meter, and engine parameter indicators. No pre-existing technical anomalies were identified.
Accident Details
The flight proceeded into a narrow valley that terminated in a mountain cirque. The aircraft was flying at too low an altitude to execute a turn or to climb over the lowest surrounding ridges. The flight instructor's intervention during the flight was too late, and the pilot lacked knowledge of the local topography. The aircraft subsequently collided with terrain. The accident site was located in a mountainous area with steep terrain.
Probable Cause
According to the BFU report, the accident was due to a collision with terrain during a flight at too low altitude in a narrow valley ending in a mountain cirque that did not allow a turn or the overflight of the lowest surrounding ridges. Factors that may have played a role were the late intervention of the flight instructor and the pilot's lack of knowledge of the local topography.