Piper PA-18 accident near Thompson Falls, Montana, February 11, 1985
On February 11, 1985 at about 5:30 pm local time, a Piper PA-18, registered N3777P, was substantially damaged in an accident near Thompson Falls, Montana (Unknown airport). It was an aerial observation flight under general aviation rules (Part 91). No one was hurt; 3 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The NTSB has not yet published a probable cause for this accident. Investigations usually take one to two years; this page updates when the final report is released.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- February 11, 1985 · about 5:30 pm local time
- Place
- Thompson Falls, Montana · Unknown · map
- Type
- Accident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Piper PA-18 · all PA-18s on the register
- Registration
- N3777P · registry record · serial 18-46665
- Damage
- Substantial damage
- Flight
- Aerial observation flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
THE ACFT NOSED OVER DURING A FORCED LNDG ON TERRAIN COVERED BY 20 INCHES OF SNOW. THE FLT WAS ON DEER SURVEY FLT THE PLT TOLD OF IMPROPER USE OF THE CARB HEAT CONTROL DURING A PERIOD OF'PERFECT' ICING CONDITIONS. THE PLTS REDUCTION OF POWER DURING MANEUVERING ALSO CONTRIBUTED TO THE BUILD UP OF ICE IN THE CARBURETOR. THE PLT WROTE IN HIS STATEMENT UNDER PREVENTATIVE RECOMMENDATIONS THAT HE SHOULD HAVE BEEN MORE AWARE OF GETTING BEHIND THE 'HEAT CURVE' OF THE ENG.
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
Pilot
- Certificate: commercial pilot
- Ratings: multi-engine land; single-engine land; single-engine sea
- Flight time: 1,710 hours in all; 1,000 in this make and model; 30 in the last 90 days
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: ctr
The aircraft
- Airframe total time: 2,375 hours
- Last inspection: 100-hour inspection, October 15, 1984; 55 hours since
- Maximum gross weight: 1,750 lb
- Seats: 2
- Landing gear: fixed
- Engine: Lycoming O-320 (piston); 0 hours total
The flight
- Departed from: MSO Thomas Falls MT at 5:00 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 090° at 5 knots
- Visibility: 5 statute miles
- Sky: overcast at 4,000 ft; scat at 4,000 ft
- Temperature: 30°F (-1°C), dew point 0°F (-18°C)
- Observation at 9:47 am from MSO
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 2 | |||
| Passengers | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
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.