Incident Overview
A helicopter on a non-revenue business flight experienced a partial loss of power. The pilot noted the N1 rpm dropping to 70% and torque decreasing to 10%. Efforts to restore power were unsuccessful, and the pilot executed a forced landing in the Grand Canyon.
Landing and Impact
The landing was made on an upward slope. During touchdown, the main rotor blades struck and severed the rear portion of the tail boom. After landing, the N1 remained at 70% with the throttle fully open.
Post-Landing Examination
An examination of the helicopter and engine revealed no cause for the loss of power. An operational check of the engine was subsequently performed, but no discrepancies were noted. The elevation of the landing site was approximately 3,500 feet.