B4/2005L Aircraft accident investigation, Copterline Oy Sikorsky S-76C+, in Tallinn Bay, Estonia on 10 August 2005

Following the accident on 10 August 2005 to the Copterline Oy helicopter Sikorsky S-76C+, nationality and registration marks OH-HCI, in Tallinn Bay in Estonia, an Aircraft Accident Investigation Commission (the Commission) was appointed under the decree No. 313 of the Minister of Economic Affairs and Communications.

In accordance with the ICAO Annex 13 Finland, as the State of Registry of the helicopter, appointed an accredited representative Mr. Hannu Melaranta, from Accident Investigation Board of Finland (AIBF) to participate in the investigation. Lieutenant Mr. Timo Lindholm and Captain Mr. Ari Anttila from the Finnish Border Guard and M.Sc. (Tech.) Mr. Markku Roschier were appointed as Mr. Melaranta’s advisers.

The Investigation Commission published the investigation report on 11 August 2008. The investigation report is available on AIBF’s website only in English. The Finnish translation is going to be published later.

SUMMARY

On 10 August 2005, a Sikorsky S-76C+ helicopter, registration OH–HCI, was operating a scheduled passenger service by Copterline between Helsinki, Finland and Tallinn, Estonia. The helicopter departed Tallinn at 12:39 hours (local time) with 12 passengers and two pilots on board. Approximately three minutes after take-off while climbing at 1380 ft above sea level, the flight data recorder showed that the flight was interrupted by a sudden helicopter pitch-up and left roll maneuver, then remained in varying attitudes of right yaw (rotation), roll and pitch for 37 seconds until impacting the water at 12:42:28 hours. There were no survivors.

The Aircraft Accident Investigation Commission determined that the cause of the accident was an uncommanded extension of the main rotor forward actuator and subsequent loss of control of the helicopter. Contributing to the uncommanded extension of the actuator was the separation of the plasma coating on one of two actuator pistons and the operator’s failure to detect the internal leakage of the main rotor forward actuator.

In the months following the accident, the Commission initiated interim safety recommendations, which resulted in NTSB Safety Recommendations A-05-33 through -35, Sikorsky All Operators Letter CCS-76-AOL-05-2001, FAA Special Airworthiness Information Bulletin SW-06-15, and an FAA Notice of Proposed Role Making (2006-SW-05 AD).

In this report, the Commission issued four additional safety recommendations addressed to Sikorsky, FAA, NTSB, Copterline and CAA-Finland.

B4/2005L Report (pdf, 2.75 Mt)