What happened
On March 30, 2011, at approximately 07:15 UTC, an EC 135P2+ helicopter departed from Innsbruck (LOJO) carrying a pilot, a flight operator, and two passengers. The flight included a scheduled stop at the Franz-Senn-Hütte to pick up an additional passenger before proceeding toward Achenkirch.
During the final leg of the flight, the aircraft entered a right-hand turn while descending toward the Achensee. Data indicates the helicopter was traveling at a high ground speed of approximately 130 knots with a significant sink rate of roughly 1,000 to 1,200 feet per minute. The aircraft maintained a flight attitude approximately 8 to 10 degrees below the horizon. The helicopter struck the surface of the lake, resulting in four fatalities.
The investigation
The investigation utilized a variety of evidence, including eyewitness accounts, manufacturer-led flight path reconstructions using virtual reality, and data from the aircraft's engine recorders, GPS, and UMS recorder. Investigators also examined the wreckage, cockpit instrumentation, and meteorological conditions at the time of the accident.
Analysis of the flight path revealed that the aircraft was in a controlled flight state under Visual Meteorological Conditions (VMC) prior to the impact. The investigation specifically looked into whether the pilot was subject to spatial disorientation, the potential for a bird strike, or physiological impairments. The investigation also noted that the water surface was in a "glassy" state, though investigators determined that the sun's position and the visibility of nearby terrain should have allowed for adequate altitude perception.
Findings
- The aircraft was in a continuous, steep descent at high speed that was inconsistent with standard low-level flight procedures.
- The pilot was described as an experienced and safety-conscious professional, making a deliberate low-altitude maneuver unlikely.
- Flicker vertigo, caused by sunlight reflecting off the rotor blades, was identified as a possible causal factor for the pilot's impairment.
- A bird strike could not be ruled out as a potential cause for the sudden change in flight path.
- No identifiable medical conditions were found during autopsy, though other physiological impairments could not be definitively excluded.