Engine And Rotor RPM Suddenly Decreased, The Helicopter Yawed To The Left And Started To Settle

Location: Thompson Falls, MT Accident Number: WPR20LA235
Date & Time: 07/21/2020, 0558 PDT Registration: N208MP
Aircraft: MCDONNELL DOUGLAS 600 Injuries: 1 None
Flight Conducted Under: Part 133: Rotorcraft Ext. Load

On July 21, 2020, at 0558 Pacific daylight time, a McDonnell Douglas 600N helicopter, N208MP, was substantially damaged when it was involved in an accident near Thompson Falls, Montana. The pilot was not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 133 rotorcraft external load operation.

The pilot stated that, as he was on an approach to a landing zone, he lowered the collective to start a vertical descent to land. At that time, the engine and rotor rpm suddenly decreased, the helicopter yawed to the left and started to settle. As the helicopter was approaching the ground fast, the pilot increased the collective to use the remaining rpm to cushion the landing. The helicopter impacted the ground and the pilot rolled the throttle to idle, but noticed that engine speed and rpm were below the normal idle parameters. When he rolled the throttle to off, he heard a grinding, "metal-to-metal" noise. The helicopter was secured for further examination.

FMI: www.ntsb.gov