Amateur-built MATHES accident near Burlington, Wisconsin, August 11, 2012
On August 11, 2012 at about 9:00 pm local time, a amateur-built MATHES, registered N31TM, was substantially damaged in an accident during enroute (cruise) near Burlington, Wisconsin. It was a personal flight under general aviation rules (Part 91). 2 people had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The pilot's improper installation of the propeller bolts, which resulted in the in-flight separation of the propeller.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- August 11, 2012 · about 9:00 pm local time
- Place
- Burlington, Wisconsin · map
- Type
- Accident
- Injuries
- 2 people had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built MATHES
- Registration
- N31TM · no longer on the register · serial 932
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot departed on a local flight during which the airplane experienced an in-flight separation of the propeller. The pilot then performed a forced landing to a field that resulted in substantial damage to the fuselage. Postaccident examination of the airplane revealed that the pilot installed the propeller bolts backwards. The bolts were also found to be improperly torqued.
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
- Part(s) separation from AC during enroute (cruise) defining event
- Part(s) separation from AC during emergency descent
- Off-field or emergency landing during landing
- Collision with terrain or object (not controlled flight into terrain) during landing
The NTSB's findings
- cause Personnel issues › Task performance › Maintenance › Installation › Pilot
- cause Aircraft › Aircraft propeller/rotor › Propeller system › (general) › Not specified
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 695 hours in all; 40 in this make and model
- Last flight review: August 16, 2010
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: rear
- Injury: minor injuries
The aircraft
- Airframe total time: 630 hours
- Last inspection: inspection type not recorded
- Seats: 2
- Landing gear: fixed
- Engine: Continental C85 (piston); 0 hours total
The flight
- Departed from: BUU Burlington WI at 8:00 pm
- Destination: BUU Burlington WI
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 010° at 5 knots
- Visibility: 10 statute miles
- Sky: clear at 5,500 ft
- Temperature: 73°F (23°C), dew point 46°F (8°C)
- Altimeter: 29.96 inHg
- Observation at 8:55 pm from BUU
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| Passengers | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
2 documents, released by the NTSB on July 22, 2013. 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 | Record of Conversation - FAA | PDF, 1 page | View Download |
| 2 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 Letter to Pilot | PDF, 2 pages | 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.