Flight History
On 31 August 1985, at 07:15 local time, a Hughes 500 helicopter, model 369 D, registration D-HETS, departed Sertã Airfield bound for Proença-A-Nova Airfield. The aircraft was owned by the German company Delta Avia and leased to the Portuguese operator HELIPORTUGAL for forest fire prevention and attack support. On board were a Portuguese commercial helicopter pilot and a passenger.
Accident Sequence
While landing at Proença-A-Nova, the helicopter maneuvered over the airfield and approached the usual landing platform. During a quick stop intended to stabilize the aircraft for landing, the tail rotor struck the ground, causing the tail rotor guard to fracture and the tail rotor itself to become inoperative. The pilot stated that he then applied collective pitch to lift the helicopter and avoid obstacles such as barrels and other equipment, flying forward about 50 meters. However, due to the damaged tail rotor drive shaft, the aircraft lost directional control, began a forced right rotation, and crashed violently into the ground.
Injuries and Damage
Both the pilot and the passenger sustained serious injuries. They were rescued and evacuated to Coimbra Hospital by the Portuguese Air Force. The helicopter was substantially damaged: main rotor blades fractured at the nose area; tail rotor blades heavily deformed; tail rotor drive shaft fractured in two places (one from torsion due to successive ground impacts, the other from bending during the final crash); tail rotor guard fractured; fuselage structure affected with buckling, especially on the left side and ventral area; windshield fractured; instrument panel heavily damaged; tail boom structure fractured; horizontal and vertical stabilizers heavily crumpled. No third-party damage occurred.
Investigation Findings
The investigation determined that the aircraft was certified, equipped, and maintained in accordance with regulations implemented by the Federal Republic of Germany. No anomalies were found in systems or components that could have contributed to the accident. The pilot was certified and qualified for the flight, with approximately 2,000 total flight hours, including 400 hours on the accident type. His medical certificate, revalidated on 26 June 1985, indicated good physical and mental condition. The fuel control unit was found at the 90° position, indicating maximum power was being used. No flight recorders were installed (not required).
Probable Cause
The probable cause determined by the investigation was the collision of the tail rotor with the ground due to the attitude taken by the helicopter during a quick stop, which caused the fracture of the tail rotor and subsequent loss of directional control.