What happened
On June 1, 2002, at approximately 08:10 UTC, an MD 520N helicopter was prepared for a private VFR flight from a company site in Ferlach, Austria, to Portoroz Airport (LJPZ). The aircraft was fully fueled, and its weight and balance were within permissible limits. The weather conditions were favorable for the intended flight.
Rather than using the authorized landing area on the company premises, the pilot opted to take off from a different location further north on the property due to ongoing construction work in the primary area. This takeoff location consisted of a paved rectangular area with a central grass patch, surrounded by two seven-meter-high hangars, two-meter-high concrete walls, and a flight roof. The helicopter was positioned on a mobile transport/landing platform.
Immediately after the engine was started and the pilot lifted the aircraft approximately 50 cm above the ground, the helicopter began to rotate clockwise around its vertical axis. After approximately two to three full rotations, the pilot was unable to arrest the yaw and attempted an emergency landing. The aircraft struck the ground with more force than usual, resulting in substantial damage to the helicopter. There were no injuries to the pilot or the two passengers.
The investigation
The investigation was initiated after the aircraft owner, who was also the pilot, notified the investigation authorities. The SUB reconstructed the event using statements from the crew, passengers, and witnesses, alongside findings from local public safety services. The investigation focused on the flight path, the takeoff environment, and the mechanical state of the aircraft.
Findings
- The helicopter showed no pre-existing technical defects upon inspection following the accident.
- The takeoff was conducted from an unauthorized area of the company premises due to construction interference at the designated site.
- The proximity of hangars, walls, and a flight roof to the takeoff position may have created aerodynamic influences that contributed to the uncontrolled rotation or interfered with the effectiveness of the NOTAR (No Tail Rotor) system.