# NTSB DEN92LA038: Thorpe T-18, N48DD, Albuquerque, NM, March 1, 1992

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: March 1, 1992, 13:00 local (20:00 UTC)
- Place: Albuquerque, NM
- Coordinates: 35.0601, -106.620552 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=35.0601&lon=-106.6206&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report June 11, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 18200
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN92LA038
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/18200/pdf
- Page: https://openairdocs.org/ntsb/DEN92LA038

## Probable cause

A FAILURE OF THE RUDDER CONTROL SYSTEM WHEN THE PILOT ATTEMPTED TO CORRECT FOR AN INADVERTENT GROUND LOOP DURING LANDING ROLL.

## Sequence of events

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

- Loss of control - on ground/water, landing - roll
  - ground loop/swerve - inadvertent, pilot in command (cause)
- Airframe/component/system failure/malfunction, landing - roll
  - flt control syst,rudder control attach points - jammed (cause)
  - flt control syst,rudder - fractured
- On ground/water encounter with terrain/water, landing - roll

## Analysis

DURING LANDING ROLL, THE PILOT INADVERTENTLY ENTERED A GROUND LOOP.  WHEN HE ATTEMPTED RUDDER INPUT TO CORRECT FOR THE GROUND LOOP, THE RUDDER CONTROL MIXING UNIT IN THE EMPENNAGE SHIFTED AND JAMMED THE RUDDER. CONTINUED PRESSURE ON THE RUDDER PEDALS BY THE PILOT FRACTURED THE LEFT RUDDER PEDAL AT THE CROSSOVER BAR.  THE AIRCRAFT WING STRUCK THE GROUND DURING THE EVOLUTION CAUSING SUBSTANTIAL DAMAGE TO THE LEFT WING.

## Aircraft

- Registration: N48DD (not matched to a registry record)
- Reported make and model: THORPE T-18
- Category: Airplane, amateur-built
- Serial number: 958
- Airframe hours: 244
- Engines: LYCOMING O-360-A1FGP 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Gordon Hall
- Registered owner: Gordon Hall
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Annual, November 30, 1991, 25 hours before
- Departed: COS, COLORADO SPRING, CO
- Airport: ABQ, Albuquerque International, runway 3, 9,000 × 50 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 47; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, valid medical--no waivers/lim.; seat: left; flight hours: 980 total, 37 in this make and model, 5 in the last 90 days, 3 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 270° at 3 knots
- Visibility: 60 statute miles
- Lowest ceiling: 20,000 ft overcast
- Temperature: 61 °F, dew point 19 °F
- Altimeter: 30.00 inHg

## 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 19920301004789A](https://openairdocs.org/incident/19920301004789A), Mar 1, 1992: Amtrth THORPT18, Albuquerque, NM, Substantial damage. Rudder tail wheel mix unit shifted, jammed left rudder causing ground loop landing. Left rudder pedal broke also.

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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