Md Helicopters Inc 600 N745MB accident near Sterling City, Texas

Probable cause

The pilot’s failure to maintain clearance from a power line pole’s static arm during forecasted gusting wind conditions, un-forecasted light turbulence, and un-forecasted low-level wind shear conditions, resulting in main rotor blade contact with the static arm and a subsequent loss of control and impact with terrain.

NTSB analysis

The helicopter departed from the remote landing zone with the pilot and an aerial lineman to conduct aerial power line system work. ADS-B data showed that the helicopter approached the target powerline pole from the west. The helicopter maneuvered around the pole, and the data subsequently terminated at the pole.

Various impact marks were observed on a static arm, about 12 ft long, at the top of the pole. The impact marks were located about 4 ft from the base of the static arm. The pole and attached wires were all found intact. The helicopter came to rest on its left side, about 103 ft away from the pole on a flat grass field. The helicopter sustained substantial damage to the main rotor system, fuselage, and empennage.

Postaccident examination of the airframe and the engine revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation.

A review of meteorological data showed that the helicopter likely encountered gusting wind conditions to 26 kts, light turbulence, and low-level wind shear (LLWS) conditions at the time of the accident.

The weather forecast for the accident time did not forecast turbulence or LLWS and there were no PIREPs or other information indicative of turbulent conditions or LLWS within 100 miles of the accident site. The closest terminal aerodrome forecast, 42 miles southeast of the accident site, did include gusting wind conditions. The actual wind conditions for the accident site were likely below the operator’s published wind limitations.

A search of archived information indicated that the pilot did not request weather information from Leidos Flight Service or through ForeFlight. The pilot did have an account through ForeFlight but only updated route strings on the accident day. It is unknown what weather information, if any, the pilot checked or received before or during the accident flight.

Based on the available evidence, it is likely the pilot failed to maintain clearance from the power line pole’s static arm during forecasted gusting wind conditions, un-forecasted light turbulence, and un-forecasted LLWS conditions, resulting in main rotor blade contact with the static arm and a subsequent loss of control and impact with terrain.

Text from the NTSB. Open the NTSB docket for CEN24FA049 for the full record.