Robinson Helicopter Company R44 II N590GG accident near Douglas, Wyoming

Probable cause

The pilot's inability to control the helicopter's descent after encountering a sudden wind shift to a tailwind while performing a near maximum gross weight landing at a high density altitude.

NTSB analysis

The airline transport pilot and three passengers departed in a reciprocating engine-powered helicopter for an aerial tour of ranch operations. The pilot reported that, before departure, about a 12- to 15-knot westerly wind prevailed. During the tour flight and on the approach to a vacant spot for landing near a cattle facility, the pilot observed light wind conditions. The pilot also noted that the power and glidepath indications were normal and that the airspeed was 30 knots at 100 ft above ground level (agl). The pilot added that "somewhere below 50 ft agl," there was a sudden, abrupt, high descent rate; as he manipulated the controls, the low rpm light illuminated, and the low rpm warning horn sounded. There was insufficient altitude to lower the collective and regain rpm before the helicopter impacted terrain and rolled to the side while the engine continued to run.

The pilot reported that there were no preimpact mechanical malfunctions or failures with the helicopter that would have precluded normal operation. After the accident, he observed a steady tailwind of at least 15 knots. Based on the available information, it is likely that, after encountering a sudden wind shift to a tailwind during landing, the helicopter entered a descent from which the pilot could not recover. Based on the conditions at the time of the accident, the calculated density altitude was 7,015 ft, and the helicopter was near the maximum gross weight of 2,500 lbs.

Text from the NTSB. Open the NTSB docket for CEN17LA219 for the full record.