Robinson Helicopter Company R44 II N744KA accident near Clayton, New Mexico

Probable cause

The pilot's loss of vertical control after the helicopter encountered a gusty tailwind while maneuvering at a low altitude and near the helicopter's maximum gross weight.

NTSB analysis

The pilot reported that 25-30 minutes into the aerial photography flight, the helicopter began to settle (descend under power) while established in a left turn from an easterly heading about 100 feet above the ground. The pilot increased collective control, but the helicopter continued to descend as it approached two sets of power lines. He stated that with full engine power, the helicopter was able to clear both sets of power lines; however, the low rotor speed warning horn sounded as the helicopter crossed over the second set of power lines. The pilot briefly reduced the collective control to regain rotor speed, but, as the helicopter approached the ground, he increased collective control in another attempt to arrest the descent. The pilot stated that the helicopter impacted terrain in a manner similar to a hard landing, bounced, and rolled over onto its left side. The pilot reported there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.

In his statement, the pilot indicated the likelihood that the helicopter's encounter with a southerly wind gust during the left turn from an easterly heading sufficiently reduced the amount of available lift from the main rotor to allow the helicopter to descend with full engine power and collective control. A nearby weather station reported gusty wind conditions from the south, with peak speeds of 32 knots. A southerly wind gust during a left turn from an easterly heading would have resulted in a tailwind condition and an associated loss of available lift from the main rotor. The pilot estimated the helicopter's weight at the time of the accident was about 9 pounds below the helicopter's certificated maximum gross weight. The pilot's maneuvering of the helicopter at a low altitude, while at nearly maximum gross weight, reduced his ability to regain vertical control before the helicopter encountered the power lines and terrain.

Text from the NTSB. Open the NTSB docket for CEN13LA507 for the full record.