Flight History
On 7 September 1993, a female private pilot departed Altenrhein at 0931 hours aboard a Cessna 152 (registration HB-CHI) for a private flight to Speck-Fehraltorf. This was her fourth flight after passing her private pilot exam on 2 August 1993. Before departure, she telephoned the airfield manager at Speck-Fehraltorf to inquire about approach and departure procedures. The approach and landing on Runway 12 were normal. After completing formalities, she departed Speck-Fehraltorf at 1032 hours to return to Altenrhein.
Accident Sequence
The pilot reported over the waypoint "Sierra" correctly on the airfield frequency. Three witnesses observed the aircraft flying from Bettswil over Matt towards the Baschlis summit and Ghöchweid. The flight altitude was estimated at approximately 150 m above ground, speed at about 120 km/h, and the engine sound was relatively weak. After overflying Matt, the aircraft initiated a climb without a change in engine sound. In a right turn, it collided with trees about 40 m below the crest of the Baschlis summit and crashed. The accident occurred at approximately 1042 hours.
Injuries and Damage
The pilot suffered severe brain injuries. The aircraft was destroyed. Forest damage occurred.
Investigation Findings
- The pilot held a valid license; no evidence of health issues.
- The aircraft was maintained according to regulations; no technical defects found.
- Weight and balance were within limits; fuel was sufficient for the planned flight.
- Weather at the accident site: 2/8 cloud cover at 1800-2000 m, 4-5/8 at 3500 m; visibility >10 km; wind variable around 2 kts; temperature 14°C, dew point 7°C; QNH 1014 hPa; sun azimuth 127°, elevation 36°.
- The pilot had drawn a flight route on an ICAO chart that passed through TMA Dübendorf (lower limit 3300 ft QNH).
- Due to retrograde amnesia from the accident, the pilot could not provide details about the flight.
Assessment
The pilot, described as very conscientious, reported at the "Sierra" waypoint after departure from Speck-Fehraltorf. The maximum altitude there is 2500 ft QNH. She may have intended to stay below 3300 ft QNH to avoid entering TMA Dübendorf without clearance. The weather was ideal and not a factor in the low altitude. The accident site lies at approximately 3300 ft QNH. Why the pilot flew over Bettswil-Matt-Ghöch instead of the direct route over Bäretswil-Bauma can only be explained by a navigation error near Bäretswil. Due to insufficient altitude when entering rising terrain and late recognition of the situation, the collision could not be avoided.