Introduction
On 15 December 1990, a Hughes HU-300C helicopter registered as HB-XUP was destroyed in an accident at St. Meinrad, Einsiedeln, in the canton of Schwyz, Switzerland. The pilot and a passenger exited the wreckage without injury.
Aircraft and Pilot
The helicopter was owned by Robert Fuchs-Bamert and operated as a private flight. The pilot, a Swiss national born in 1963, held a professional helicopter pilot license. He had accumulated a total of 123 flight hours, of which 112 hours were on the accident type, all within the previous 90 days.
Flight History
The pilot rented the helicopter from Fuchs Helikopter in Schindellegi on 14 December 1990 for a private flight to the Grisons region (Bündnerland). The following day, he intended to return to Schindellegi with a passenger. After crossing the Linth plain, he attempted to fly over the Etzel ridge approximately 1 kilometer east of the Etzel pass summit at an altitude just below 1,000 meters above sea level. He flew at a few meters above ground, following a high-voltage power line, in severely reduced visibility. The pilot initiated a turn, during which he lost ground reference and control of the helicopter. The aircraft struck a snow-covered, gently sloping meadow and was destroyed.
Findings
- The pilot held a valid license to conduct the flight.
- The helicopter was certified for VFR operations and had been properly maintained.
- No technical defects were found that could have caused the accident.
- Weight and balance were within permissible limits.
- Weather conditions at the accident site, as reported by the Swiss Meteorological Institute (MZA), included: 7/8 to 8/8 cloud cover with a base at 600 to 800 meters above sea level, light snowfall, visibility of 1 to 2 kilometers with local reductions, variable wind around 2 knots, temperature and dew point near 5°C, and QNH 1018 hPa. Hazards included poor visibility in snowfall and over snow-covered terrain.
Assessment
The weather across the northern side of the Alps was very poor for visual flight. The cloud base was low, and horizontal visibility was only hundreds of meters in places. The pilot wished to return the helicopter (the scheduled arrival time was 1300 local time). After crossing the Linth plain, he flew a direct line to the destination at low altitude along a power line. While flying uphill beside trees, he maintained adequate ground reference. However, when he reached the crest at the end of the forest, only a snow-covered meadow lay ahead, and visibility rapidly deteriorated. He initiated the turnaround at a maximum height of 25 meters above ground with horizontal visibility less than 300 meters—too late. The pilot attempted to land but lost ground reference during the turn, becoming disoriented as to direction, and collided with the terrain. The impact was cushioned by approximately 50 centimeters of snow.
Cause
The accident was caused by flying with insufficient visual references under visual flight rules (VFR), leading to loss of orientation and control of the helicopter. Contributing factors included a late decision to abort the flight and possibly increased pilot workload from pressure to return the helicopter.