The preliminary report by Estonia’s air accident investigators on the 10 August fatal Sikorsky S-76 crash in Tallinn Bay says the helicopter went out of control for reasons not yet established, writes David Learmount.
The flight data recorder indicates that the aircraft pitched up and banked left suddenly, then began to spin right, turning through 13 complete rotations in the 30s before it hit the surface and sank quickly.
The Copterline S-76 took off from Tallinn for the short scheduled flight to Helsinki, Finland, and had just established cruise at a height of 1,500ft (460m) and airspeed of 130kt (240km/h). The problems began when the captain – the pilot flying (PF) – announced his intention to add power and climb to 2,000ft.
Then, says the report, the PF began to raise the collective, which was followed by a rapid nose-up movement of the cyclic control through “approximately half the maximum travel”. A second later the cyclic moved fully forward “for a very short period”. According to the cockpit voice recorder the cyclic movement aft “was followed by the exclamation of the [PF] and a warning signal”.
At the same time the vertical acceleration increased from 1 to 3G in 1.5s, the pitch had increased to 40° nose-up, the roll to 40° left, and the heading had changed from 355° to 320°. The helicopter climbed about 200ft and stayed there for 10s before an “unstable” rapid spinning descent to impact. The captain of a pilot boat 3km away reports hearing “consecutive loud banging sounds” from the helicopter.
At impact both engines were working and both rotors were turning. An autopsy established that all 14 people on board died of drowning, says the report. The inquiry is continuing.
Source: Flight International
