# NTSB FTW91LA117: Thorp T-18CW, N83MK, Wimberley, TX, July 5, 1991

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: July 5, 1991, 13:18 local (18:18 UTC)
- Place: Wimberley, TX
- Location: 29.9841° N, 98.0903° W: Placed by OpenAirDocs: center of Wimberley, TX, within about 6 miles (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=29.9841&lon=-98.0903&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor, 1 uninjured
- Status: Completed, report March 31, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 23362
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW91LA117
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/23362/pdf
- Page: https://openairdocs.org/ntsb/FTW91LA117

## Probable cause

THE FAILURE OF THE AIRPORT PERSONNEL TO MAINTAIN THE AIRSTRIP IN AN OPERABLE CONDITION AND THE PILOTS FAILURE TO MAINTAIN RUNWAY ALIGNMENT ON TOUCHDOWN.

## Sequence of events

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

- On ground/water encounter with terrain/water, landing - roll
  - terrain condition - high vegetation
  - proper alignment - not attained, pilot in command (contributing factor)
  - runway maintenance - inadequate, airport personnel (cause)
- Loss of control - on ground/water, landing - roll
- On ground/water encounter with terrain/water, landing - roll
  - terrain condition - dirt bank/rising embankment
  - ground loop/swerve - inadvertent, pilot in command
- Nose over, landing - roll

## Analysis

DURING A LANDING ON A GRASS AIRSTRIP THE PILOT FAILED TO MAINTAIN RUNWAY ALIGNMENT ON TOUCHDOWN AND LOST CONTROL WHEN HIS LEFT MAIN WHEEL ENTERED LONG GRASS. LEFT WING CONTACTED 5 FOOT TALL WEEDS ADJACENT TO THE 40 FEET WIDE AIRSTRIP.  THE AIRPLANE VEERED LEFT AND STRUCK A LARGE ANT MOUND RESULTING IN THE AIRPLANE GROUND LOOPING TO THE INVERTED POSITION.  THE PILOT REPORTED THAT TOUCHDOWN OCCURRED TEN FEET LEFT OF RUNWAY CENTER.

## Aircraft

- Registration: [N83MK](https://openairdocs.org/deregistered/N83MK-2006-03-07), registration cancelled 2006-03-07, S/N 1367, built 1984 (OpenAirDocs)
- Reported make and model: THORP T-18CW
- Registry model: [Lipscomb Karl THORP T-18CW](https://openairdocs.org/model/lipscomb-karl-thorp-t-18cw) (registry code 89510H7) (OpenAirDocs)
- Registry engine: [Lycoming O&VO-360 series](https://openairdocs.org/engine/lycoming-o-vo-360-series) (registry code 41514, reciprocating) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: 1367
- Engines: LYCOMING O-360 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: James W. French
- Registered owner: James W. French
- Departed: T98, SAN MARCOS, TX
- Airport: NONE, Woodbreck, runway 15, 2,200 × 40 ft, grass/turf

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 50; private; airplane ratings: single-engine land; medical: class 2, valid medical--w/ waivers/lim; flight hours: 2,594 total, 740 in this make and model, 2,502 as pilot in command, 40 in the last 90 days, 15 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 140° at 5 knots
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: -0 °F, dew point -0 °F
- Observed at: AUS, 40 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 19910705026429A](https://openairdocs.org/incident/19910705026429A), Jul 5, 1991: Amtrth THORPT18, Winberly, TX, Substantial damage. Failed maintain center off narrow grass strip landing. Wing hit tall weeds veered into ant mound. Flipped over.

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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