NTSB Identification: WPR10FA295
14 CFR Part 133: Rotorcraft Ext. Load
Accident occurred Wednesday, June 16, 2010 in Donnelly, ID
Probable Cause Approval Date: 03/08/2012
Aircraft: KAMAN AEROSPACE CORP K-1200, registration: N134WC
Injuries: 1 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

While lifting a heavy external load off the ground, the leading edges of two of the logging helicopter's counter-rotating main rotor blades collided with each other. The collision resulted in the destruction of a significant portion of both of those blades and the separation of one of the two main rotor pylons. Control of the helicopter was no longer possible, and it impacted the terrain in the inverted position. Detailed postaccident examinations of the helicopter’s components, tests, and witness interviews did not reveal evidence of any pre-existing anomalies or malfunctions or of any pilot action that would have led to the blades colliding. Although the helicopter was operating at an estimated 288 pounds above its maximum certified gross weight of 12,000 pounds, there is no evidence that this played a role in causing or contributing to the blade-to-blade contact. The event that initiated the accident sequence was not determined.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The collision of two counter-rotating main rotor blades for undetermined reasons, which resulted in a loss of control.

Full narrative available

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