Robinson Helicopter R22 BETA N4052G accident near Tucson, Arizona

Probable cause

A loss of engine power due to the pilot's failure to utilize carburetor heat while maneuvering.

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NTSB analysis

The pilot was flying a series of maneuvers when he broadcasted to the local air traffic controller a loss of engine power. During the forced landing, the helicopter impacted terrain and was found resting on its right side. The pilot did not recall the events of the accident.

During the postaccident airframe and engine examinations, the engine was started and operated over a range of power settings, from idle to full power. After several minutes of normal operation, the engine was shut down. Further examination of the engine and airframe revealed no evidence of any mechanical malfunctions or failures that would have precluded normal operation.

During the cabin examination, the carburetor heat control knob was found in the down or “OFF” position. The latch that locks the carburetor control knob in the down position was found engaged around the shaft of the control knob. The latch and its attachment bracket were bent upward. A review of the carburetor icing chart revealed that the helicopter was operating in an area conducive to serious icing at cruise power. It is likely that the pilot did not utilize carburetor heat, which resulted in the accumulation of ice in the carburetor and the subsequent loss of engine power.

Text from the NTSB. Open the NTSB docket for WPR12FA066 for the full record.