6 Aug 2008: SIKORSKY S-61N (N612AZ) — USDA Forest Service — Weaverville, CA

9 fatalitiesWeaverville, CA, United States

A helicopter transporting firefighters crashed into trees and terrain during its initial climb in mountainous terrain.

What happened

On August 5, 2008, at approximately 1941 Pacific daylight time, a Sikorsky S-61N helicopter, registration N612AZ, crashed during the initial climb following takeoff from Helispot 44 (H-44) near Weaverville, California. The aircraft was operating a public flight for the U.S. Forest Service to transport firefighters to another helispot. The helicopter was located at an elevation of approximately 6,000 feet in mountainous terrain.

During the climb, the aircraft struck trees and terrain. The resulting impact forces and a postcrash fire destroyed the helicopter. The accident resulted in 9 fatal injuries, including the pilot-in-command, the safety crewmember, and seven firefighters. Additionally, the copilot and three firefighters sustained 4 serious injuries.

At the time of the accident, visual meteorological conditions were present with a visibility of 10 statute miles and winds from 150 degrees at 07 knots. A company visual flight rules flight plan had been filed for the flight.

Probable cause

The accident was caused by Carson Helicopters' intentional understatement of the helicopter's empty weight, the alteration of the power available chart to exaggerate lift capability, and the use of unapproved torque specifications in performance calculations. These actions led the pilots to rely on calculations that overestimated the aircraft's load-carrying capacity and lacked an adequate performance margin. Additionally, there was insufficient oversight by the U.S. Forest Service and the FAA.

Contributing factors

Related operating infoOperatorPilotFAA/RegulatorOther governmentFlight crewDesignFluid conditionAvailability of related infoNot installed/available