Bell 206 N275AE accident near Union City, Tennessee

Probable cause

The pilot’s inadvertent slope landing and attempted recovery, which resulted in an incipient dynamic rollover, mast bumping, and separation of the main rotor.

NTSB analysis

The pilot, flight nurse, and flight paramedic were conducting a flight for a public relations event. None of the three crewmembers had previously landed at this landing zone (LZ). A company flight nurse was on the ground at the LZ informing the flight crew of obstacles in the area.

The pilot conducted a low reconnaissance and initiated a steep approach into the LZ. All obstacles were observed and called out by crewmembers as they continued the approach. The terrain appeared to the crew to be flat in all directions. The pilot began to set the helicopter on the ground from a stabilized hover. As the pilot lowered the collective to set the skids on the ground, the skid toes and the forward half of the skids made ground contact; however, from just aft of the pilot’s seat, the terrain sloped downward at a 10°-to-15° angle. Once the collective was lowered to the bottom stop, the helicopter rocked backwards to a tail-low attitude.

The pilot and crew felt the tail stinger make ground contact and assumed that the tail rotor had impacted the ground. The pilot then applied upward collective and forward cyclic, which forced the front of the skid toes tightly against the terrain. The application of upward collective resulted in the helicopter entering an incipient dynamic rollover, aggressively rolling to a 45°-to-60° nose-low attitude. The pilot applied aft cyclic to counter the nose low attitude, and mast bumping occurred when the droop (static) stops came in to contact with the mast. The main rotor then separated from the mast and departed the helicopter. The circumstances of the accident are consistent with the pilot’s attempted recovery following a slope landing, which resulted in incipient dynamic rollover, mast bumping, and separation of the main rotor.

Text from the NTSB. Open the NTSB docket for ERA18LA020 for the full record.