Robinson R22 N787SH accident near Sterling City, Texas

Probable cause

A loss of control during the landing approach for reasons that could not be determined based on the available information.

NTSB analysis

The pilot of the helicopter was approaching to land on a trailer following a short local flight. A witness saw the pilot abort the landing approach and stated that the helicopter backed away from the trailer, began to climb, then entered a "violent" counterclockwise spin as it climbed to about 20 to 25 ft above the ground. The helicopter spun 4 or 5 times, then the witness heard a loud noise like an engine backfire and the helicopter "fell" to the ground and came to rest on its right side.

Examination of the airframe, drive systems, flight controls, and engine did not reveal any pre-impact mechanical anomalies that would have resulted in a loss of control.

The helicopter was configured with a single set of flight controls (pedals, collective, and cyclic) on the right side; the left side controls were not installed, and the cover plate for the removed left pedal assembly was not installed. Three metal ammunition boxes containing tools and loose shotgun shells were recovered from the debris field. During postaccident examination, the boxes were placed on the left side floor to determine whether they may have interfered with pedal movement. The edge of the most-forward box covered the top of the left side pedal receiver when the right pedal was positioned aft of neutral. Shotgun shells were recovered from the left floor area, the belly area, and in the debris field. One shell had a dent in the plastic shell; however, the origin of the dent could not be confirmed. Due to impact damage to the floor and pedal assemblies, whether any of these items may have interfered with pedal movement during the flight could not be determined.

The pilot had over 20,000 hours in the type of helicopter. No mechanical anomalies were found that could have precluded normal operations. It is possible that the counterclockwise spin could have been a result of pedal control interference from the ammo cans or shotgun shells on the uncovered left pedal assembly; however, control interference could not be determined conclusively.

Text from the NTSB. Open the NTSB docket for CEN18FA244 for the full record.