NTSB: Firefighting chopper lost power before crash

SAN FRANCISCO (AP) — An initial investigation into a deadly helicopter crash that killed nine people in Northern California earlier this month has found that the chopper's main rotor lost power during takeoff.

The Sikorsky S-61N helicopter hit trees after losing power and fell out of the air over the Shasta-Trinity National Forest, according to a preliminary crash report released Thursday by the National Transportation Safety Board.

Investigators analyzed wreckage recovered from the crash site to determine that the rotor malfunctioned, an NTSB spokeswoman said. The agency reported earlier that witnesses said the helicopter took off more slowly than normal before slamming into a hillside.

The report says the firefighting aircraft came to rest on its left side before bursting into flames. Four of the 13 people on board survived with various injuries.

A fire-damaged voice-data recorder salvaged from the burned aircraft was sent to its British manufacturer, which determined that both the cockpit voice recording and flight data contained on the device were still intact, NTSB spokeswoman Bridget Serchak said. The agency plans to analyze the data in the coming weeks, she said.

The helicopter was ferrying firefighters away from a remote mountain site on the front lines of a stubborn wildfire when it crashed the evening of Aug. 5.

Worsening weather conditions forecast for the area prompted the decision to fly about 50 firefighters out of the Trinity Alps Wilderness.

The helicopter had completed two trips and just refueled before it picked up the third group and made the ill-fated takeoff. At the time of the accident, visibility was good enough that the pilots did not need to rely on instruments to make the flight, the NTSB report said.

The two-month-old wildfire the firefighters were battling before the crash was 84 percent contained Thursday after charring more than 44 square miles.

The blaze is part of a series of fires sparked by a massive lightning storm in late June that have burned more than 400 square miles across the Shasta-Trinity forest.

Farther north in the Klamath National Forest, a 70-square-mile blaze started by the same storm was still just 35 percent contained. The fire was burning in a remote section of the forest and did not threaten any inhabited areas, fire officials said.

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Fonte: Flight Safety Information 26/08/2008.