Amateur-built THORP T-18 accident near Austin, Nevada, December 16, 1989
On December 16, 1989 at about 1:56 am local time, a amateur-built THORP T-18, registered N111GC, was destroyed in an accident near Austin, Nevada. It was a personal flight under general aviation rules (Part 91). 1 person was killed. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
AN IMPROPER MAJOR ALTERATION PERFORMED BY THE PILOT. AS A RESULT OF THIS MODIFICATION, THE PROPELLER FAILED IN FLIGHT.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- December 16, 1989 · about 1:56 am local time
- Place
- Austin, Nevada · map
- Type
- Accident
- Injuries
- 1 person was killed.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built THORP T-18
- Registration
- N111GC · registry record · serial 387
- Damage
- Destroyed
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
DURING A CROSS COUNTRY FLIGHT, THE PILOT MADE AN UNSCHEDULED LANDING AT AN AIRPORT TO CHECK ON A NOISE. SHORTLY AFTER LANDING, THE FLIGHT CONTINUED. RADAR RETURNS INDICATE THAT THE AIRPLANE DEPARTED THE AIRPORT ON A NORTHERLY HEADING AND CLIMBED TO 11,900 FEET THEN BEGAN TO DESCEND, TURNING WESTERLY AWAY FROM RISING TERRAIN. THE AIRPLANE COLLIDED WITH HILLY TERRAIN APRX 14 MILES FROM THE AIRPORT. ONE PROPELLER BLADE HAD SEPARATED AND WAS NOT LOCATED. A METALLURGICAL TEST REVEALED THAT THE BREAK WAS DUE TO HIGH CYCLE BENDING STRESSES INDUCED BY RESONANT VIBRATION. RESEARCH OF THE AIRPLANE'S HISTORY REVEALED THAT ANOTHER ENGINE (DIFFERENT FROM WHICH THE AIRCRAFT WAS ORIGINALLY CERTIFICATED) HAD BEEN INSTALLED ON THE AIRPLANE AND THAT THE PROPELLER (ORIGINAL FROM THE FIRST ENGINE) AT SOME TIME HAD BEEN CUT AND REPITCHED.
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: private
- Ratings: single-engine land; instrument: airplane
- Flight time: 1,732 hours in all; 1,602 in this make and model
- Medical certificate: Class 3 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 1,602 hours
- Last inspection: inspection type not recorded
- Maximum gross weight: 1,650 lb
- Seats: 2
- Landing gear: fixed
- Engine: Lycoming O-320-E2A (piston); 0 hours total
- Fire on the ground
The flight
- Departed from: 9U3 Autsin NV at 1:30 am
- Destination: TWF Sun Valley ID
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Visibility: 20 statute miles
- Temperature: 43°F (6°C), dew point 19°F (-7°C)
- Altimeter: 30.00 inHg
- Observation at 1:51 am from RNO, 117 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The docket at the NTSB holds the report as a PDF and the investigation's photographs and documents. This site never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number SEA90FA030.