Experts solve Copterline mystery

  • 2006-08-09
  • By TBT staff

UNANSWERED: Nearly a year after the Sikorsky S-76C+ helicopter crashed, investigators have agreed on the exact cause.

TALLINN - Experts have concluded that a servo malfunction was, in fact, what caused the Finnish Copterline helicopter to crash a year ago in the Bay of Tallinn.

Tonu Ader, vice chairman of the commission who met with representatives of the helicopter's manufacturer, Sikorsky, in the United States last week, told the Baltic News Service that the helicopter crashed because of a rotor servos malfunction. He added that, although the commission's report will not be finished before this fall, their conclusion would not change.
While the manufacturer finally agreed that it was a servo malfunction that led the helicopter to crash, the commission and the manufacturer still differed on the exact cause.

"Although representatives of the helicopter's manufacturer do not directly agree with this, the in-depth investigation into the causes of the helicopter crash leaves no room for doubt as regards to the reasons why the helicopter came down. The aircraft was brought down because of a main rotor servo malfunction, which resulted from the fact that parts of the plasma-sprayed coating that is made from a mix of copper and aluminium had broken off from the piston crown," Ader told the Baltic News Service.

A press release by the Estonian Ministry of Economy and Communications reports that representatives from the U.S. National Transportation Safety Board said that they, too, had concluded that the accident was caused by the uncontrolled self-extending of one of the servos.
"Representatives of the Sikorsky plant had to admit that their earlier claims as regards a waterspout on the Bay of Tallinn that may have brought down the helicopter were wrong. They admitted that there was no waterspout above the Bay of Tallinn at the time when the helicopter fell, and that the servo failure proved fatal for the helicopter. At the same time, their opinion as regards the cause of the malfunction still differs from that of the investigating commission," Ader said.

The ministry said the manufacturer's version that a waterspout had caused the accident was also regarded as ungrounded by the National Transportation Safety Board.
Ader added that the Sikorsky plant had still not answered requests for tests that would satisfy the investigating commission.
"The Sikorsky company had conducted tests on the main rotor servo, but they hadn't taken into account our requirements and the results of the tests didn't meet our expectations," Ader said.
Following Ader's visit to the United States, the Sikorsky plant agreed to conduct additional tests in line with the investigating commission's demands. The outcome of those tests is due to be received in October, after which the final report can be completed.

The Sikorsky S-76C+, owned by the Copterline company and operated by a Finnish crew, crashed into the Bay of Tallinn minutes after takeoff from Tallinn to Helsinki on Aug. 10, 2005. All 12 passengers and two crew members onboard were killed in the accident.