# NTSB SEA90FA030: Crawford-Gordon Thorp T-18, N111GC, Austin, NV, December 16, 1989

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Field investigation · Final report
- Date: December 15, 1989, 17:56 local (Dec 16, 1989, 01:56 UTC)
- Place: Austin, NV
- Coordinates: 39.540744, -117.18946 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=39.5407&lon=-117.1895&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 1 fatal
- Status: Completed, report July 22, 1992
- Report: Approved by Office Director
- Safety recommendations: Yes
- NTSB case key (mKey): 41096
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA90FA030
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/41096/pdf
- Page: https://openairdocs.org/ntsb/SEA90FA030

## Probable cause

AN IMPROPER MAJOR ALTERATION PERFORMED BY THE PILOT. AS A RESULT OF THIS MODIFICATION, THE PROPELLER FAILED IN FLIGHT.

## Analysis

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.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, climb - to cruise
  - propeller system/accessories,blade - fatigue (contributing factor)
  - maintenance,major alteration - improper, pilot in command (cause)
- Forced landing, descent - emergency
- In flight collision with terrain/water, descent - emergency
  - terrain condition - mountainous/hilly

## Aircraft

- Registration: [N111GC](https://openairdocs.org/deregistered/N111GC-1992-10-23), registration cancelled 1992-10-23, S/N 387 (OpenAirDocs)
- Reported make and model: CRAWFORD-GORDON THORP T-18
- Registry model: [Crawford-Gordon THORP T-18](https://openairdocs.org/model/crawford-gordon-thorp-t-18) (registry code 89510D1) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: 387
- Airframe hours: 1602
- Engines: LYCOMING O-320-E2A 160 horsepower reciprocating
- Damage: Destroyed
- Fire: On-Ground
- Flight: Personal, Part 91
- Registered owner: Gordon B. Crawford
- Airworthiness certificate: Special, Experimental (Special)
- Departed: 9U3, AUTSIN, NV
- Destination: TWF, SUN VALLEY, ID

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 53; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, valid medical--no waivers/lim.; seat: left; toxicology performed; flight hours: 1,732 total, 1,602 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 20 statute miles
- Lowest ceiling: none
- Temperature: 43 °F, dew point 19 °F
- Altimeter: 30.00 inHg
- Observed at: RNO, 117 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19891215051329A](https://openairdocs.org/incident/19891215051329A), Dec 15, 1989: Amtrth THORPT18, Austin, NV, Destroyed, 1 fatal. Crashed and burned in mountainous area. Prop blade had failed due to fatigue. Prop had been modified below standards

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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