What happened
On July 23, 2010, at approximately 14:40 UTC, a Bell 204B helicopter was performing an external load operation near Hinterthal, in the municipality of Maria Alm, Salzburg. The mission involved transporting a concrete bucket to a site for the construction of a cable car support foundation.
Earlier that day, the pilot had paused operations due to fog and rain. After the weather cleared unexpectedly, the pilot decided to resume the final two planned rotations. During the unloading process at the far right side of the foundation, the pilot attempted to turn the aircraft to the left using left pedal input. During this maneuver, the tail rotor struck a conifer tree.
The collision caused significant damage to the tail rotor and the tail gearbox housing, leading to an uncontrolled clockwise rotation of the aircraft. The pilot attempted an autorotative landing and released the concrete bucket, but a main rotor blade struck the tail boom, severing it. The helicopter subsequently struck the forest floor nearly vertically. The pilot sustained fatal injuries, and the aircraft was a total loss.
The investigation
The Austrian SUB investigation examined the flight sequence, the aircraft's technical condition, and the environmental factors. Investigators reconstructed the event using eyewitness testimony from ground crew and police findings. The investigation confirmed that the pilot was highly experienced, with nearly 18,000 external load flights recorded in his logbook.
Technical examinations of the Bell 204B revealed no evidence of mechanical system failure or malfunctions prior to the impact with the tree. The investigation also noted that the pilot was operating from the left seat using a specialized bubble window for visibility. While the weather had caused a temporary interruption to the flight schedule, it was not a direct cause of the impact.
Findings
- The primary cause was insufficient horizontal clearance from obstacles due to the use of a sling length that was too short for the maneuver.
- There was no appropriately positioned signal person (marshaller) present to warn the pilot of the encroaching tree limbs.
- The pilot's situational awareness may have been diminished by the decision to resume the mission following the weather-related delay.
- The ground crew members, acting as signal persons, were unable to accurately assess the clearance between the aircraft and the surrounding trees.
- The structural failure of the pilot's seat during the impact significantly reduced the pilot's chances of survival.