B5/2005L Helicopter accident in Paltamo on 2 September 2005

At Paltamo Metelinniemi golf course occurred September 2nd 2005 about 13.30 Finnish time a flight accident, in which a Bell 206B helicopter OH-HLP, owned and operated by First Invest Oy, fell down in a water pool during a photographing flight. Besides the pilot there were two other people in the helicopter, one of which was lightly injured. The helicopter was badly damaged. To investigate the accident the Accident Investigation Board Finland set an investigation board with investigator Juhani Hipeli nominated as its chairman and investigators Antti Kaarnamo and Jari Huhtala as members.

When the accident occurred the golf course routes were being video filmed from the helicopter's left rear seat for a presentation video. The helicopter flew following the right side of the route above the tree tops at about 150-200 ft altitude above ground at a speed of 20-30 knots. The route curves to the left and towards the end to the right. When approaching the route end the pilot felt the helicopter nose unintentionally turning to the right. He tried to recover control of the helicopter with control inputs but the turning to the right continued and the rotation speed increased. The helicopter rotated around its vertical axis an estimated 1.5 to 3.5 revolutions before the landing gear hit the water. The helicopter banked to the left and the main rotor struck into water and then into the left side of the helicopter. Then the helicopter turned upside down so that the landing gear, fuselage bottom and the tail remained partially above water. All three people were rescued by themselves from the helicopter filled with water.

According to the opinion of the investigation board the reason for ending up into an uncontrolled flight state with unintentional rotation to the right around the vertical axis was a loss of effectiveness of the helicopter tail rotor. The low flying speed, sideslip to the left when the right pedal is pushed, turn to the right, relatively high flying weight and tail wind contributed to the loss of effectiveness. The torque, imposed on the helicopter in low speed flight by the main rotor power, is balanced by the tail rotor thrust. The torque, caused by the combined contributions mentioned above, exceeded the tail rotor effectiveness leading to the unintentional rotational motion and loss of control of the helicopter. It also transpired in the investigation that the pilot had incomplete knowledge about the helicopter's handling characteristics and aerodynamics probably due to a deficient training.

The investigation board considers that the basic cause of the accident is the pilot's lacking knowledge about the helicopter's handling characteristics and aerodynamics. The pilot lost control of the helicopter when flying at low speed in tail wind a right turn with sideslip to the left, when due to the combined effects the tail rotor lost its effectiveness. The pilot did not identify the flight state and was not able to hinder the rotational motion around the vertical axis so that the helicopter fell into water. Contributing factors were the pilot's small experience in photographing flights and the tail wind.

The investigation board presents as safety recommendations that Finnish Civil Aviation Administration should take measures to increase knowledge of the reduction of tail rotor effectiveness in helicopter training programs, and that it should check the company's requirements of maintenance and should monitor compliance of the requirements.

B5/2005L Report (pdf, 0.95 Mt)