Mcdonnell Douglas 600 accident near Thompson Falls, Montana, July 21, 2020
On July 21, 2020 at about 11:58 am local time, a 1998 Mcdonnell Douglas 600 (helicopter), registered N208MP, was substantially damaged in an accident during maneuvering (hover) near Thompson Falls, Montana. It was an external-load flight under external-load helicopter rules (Part 133). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A partial loss of engine power for reasons that could not be determined based on available evidence.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 21, 2020 · about 11:58 am local time
- Place
- Thompson Falls, Montana · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Mcdonnell Douglas 600 N, built 1998
- Registration
- N208MP · no longer on the register · serial RN042
- Damage
- Substantial damage
- Flight
- External-load flight · external-load helicopter rules (Part 133)
The NTSB's narrative final · quoted from the NTSB record
While on an approach to the landing zone, the pilot lowered the collective to start a vertical descent to land. At that time, the engine and rotor speeds suddenly decreased, the helicopter yawed to the left and started to settle. Because the helicopter was approaching the ground fast, the pilot increased the collective to use the remaining engine power to cushion the landing. The helicopter impacted the ground, and the pilot rolled the throttle to idle, but noticed that engine speed and rotor rpm gauges were below the normal idle parameters. When he rolled the throttle to off, he heard a grinding "metal-to-metal" noise, and the rotor blades stopped spinning almost immediately. Data downloaded from the onboard incident recorder captured a “low rotor RPM” event during the flight, followed by “Flameout” and “Ng Low” triggers. According to the data, the full authority digital engine control system (FADEC) attempted to re-light the engine for the next 53 seconds until the throttle was rolled to cut-off; however, the engine did not restart. A postaccident examination of the engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation, and the reason for the low rotor rpm triggering event could not be determined.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Loss of engine power (partial) during maneuvering (hover) defining event
The NTSB's findings
- Aircraft › Aircraft power plant › (general) › (general) › Unknown/Not determined
Pilot
- Certificate: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine sea; instructor: helicopter; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 6,450 hours in all; 150 in this make and model; 140 in the last 90 days; 65 in the last 30 days; 6,300 as pilot in command; 400 on instruments
- Medical certificate: Class 2 (without waivers/limitations)
- Seat: left
- Injury: no injuries
The aircraft
- Airframe total time: 2,984.6 hours
- Last inspection: annual inspection, May 7, 2020
- Maximum gross weight: 4,100 lb
- Seats: 2
- Landing gear: fixed
- Engine: Rolls Royce M250-C47M (turboshaft); 2,984 hours total
The flight
- Departed from: Thompson Falls MT at 2:54 pm
Weather at the time
- Light: daylight
- Wind: from 280° at 3 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 52°F (11°C), dew point 50°F (10°C)
- Altimeter: 29.95 inHg
- Observation at 5:55 am from SZT
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
6 documents, released by the NTSB on June 30, 2022. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 11 pages | View Download |
| 2 | Pilot's Statement | PDF, 1 page | View Download |
| 3 | Rolls-royce Engine Report | PDF, 16 pages | View Download |
| 4 | Ecm Values | PDF, 3 pages | View Download |
| 5 | Statement of Party Representatives to NTSB Investigation | PDF, 2 pages | View Download |
| 6 | Release of Aircraft Wreckage, NTSB Form 6120.15 | PDF, 1 page | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.