Accident Overview
On 23 May 2019, at approximately 10:00 UTC, a Eurocopter EC 135 T2+ helicopter operated by an Austrian commercial operator was involved in an accident during a rescue mission in alpine terrain near St. Anton am Arlberg, Tirol, Austria. The helicopter was configured for helicopter emergency medical services (HEMS) and was crewed by a pilot, a flight physician, and a flight rescuer.
Flight History
The helicopter was alerted at 08:53 UTC and departed from its base in Zams at 08:56 UTC. It landed on a forestry road near the accident site, then repositioned at 09:24 UTC to a nearby intersection of forestry roads to shorten the patient transport distance. The engines were kept running to prevent the helicopter from sinking into soft ground. During loading of the patient through the left sliding door, the crew noticed the helicopter began to slide. The flight physician alerted the pilot via radio, after which the helicopter entered an uncontrolled rotation around its vertical axis.
Investigation Findings
The investigation, conducted by the Austrian safety investigation board (Sicherheitsuntersuchungsstelle des Bundes), examined the flight recorder data, witness statements, and medical records. Analysis of the pilot's medical history and post-accident examinations revealed that the pilot had suffered a tonic-clonic seizure (grand mal) during the mission. The pilot had a pre-existing condition involving a head trauma from a previous incident, which was known to the medical authorities. The seizure occurred without prior warning and led to the pilot's incapacitation, resulting in the loss of control.
Probable Cause
The probable cause of the accident was the pilot suffering a tonic-clonic seizure (grand mal) during the emergency mission, leading to uncontrolled rotation and impact with terrain.