# NTSB DEN90DTE01: Lanier Thorp T-18, N18FL, Colorado City, CO, November 24, 1989

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Final report
- Date: November 24, 1989, 07:54 local (14:54 UTC)
- Place: Colorado City, CO
- Coordinates: 37.940368, -104.840972 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=37.9404&lon=-104.8410&mi=10
- Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 1 fatal
- Status: Completed, report September 30, 1991
- Report: Approved by Office Director
- NTSB case key (mKey): 17794
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN90DTE01
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/17794/pdf
- Page: https://openairdocs.org/ntsb/DEN90DTE01

## Probable cause

LOSS OF ENGINE POWER WITH CARBON FOULING OF THE SPARK PLUGS, AND FAILURE OF THE PILOT TO MAINTAIN ADEQUATE AIRSPEED, WHICH RESULTED IN AN INADVERTENT STALL.

## Sequence of events

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

- Loss of engine power(total) - nonmechanical, takeoff - initial climb
  - ignition system,spark plug - fouled (cause)
- Forced landing, descent - emergency
- Loss of control - in flight, descent - emergency
  - airspeed - not maintained, pilot in command (cause)
  - stall - inadvertent, pilot in command (cause)
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

A WITNESS SAW THE PLT PREFLIGHT THE ACFT.  AFTER HE TOOK OFF, THE ACFT ENTERED A STEEP DESCENT & CRASHED A SHORT DISTANCE FROM THE END OF THE RWY.  AN EXAM OF THE ENG REVEALED THAT ALL SPARK PLUGS WERE CARBON FOULED.  THE HOME BUILT ACFT HAD A TOTAL OF 40 HRS FLT TIME.  THE ENG HAD A TOTAL TIME OF 42 HRS TSMO.  THE OWNER/PLT HAD CHANGED THE CARBURETOR & SPARK PLUGS AFTER THE ACFT HAD FLOWN 6 HRS & THE ACFT HAD FLOWN 13 HRS SINCE THE LAST INSPN.  NO PREIMPACT PART FAILURE WAS FOUND.

## Aircraft

- Registration: [N18FL](https://openairdocs.org/deregistered/N18FL-1989-12-11), registration cancelled 1989-12-11, S/N 555 (OpenAirDocs)
- Reported make and model: LANIER THORP T-18
- Registry model: [Lanier Frank J THORP T-18](https://openairdocs.org/model/lanier-frank-j-thorp-t-18) (registry code 89510M3) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: 555
- Airframe hours: 38
- Engines: LYCOMING O-290-G 125 horsepower reciprocating
- Damage: Destroyed
- Flight: Personal, Part 91
- Registered owner: Lanier, Frank J.
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Unknown, November 14, 1989, 13 hours before
- Departed: CO22
- Destination: CO22
- Airport: CO22, Greenhorn Valley, runway 26, 3,900 × 36 ft, grass/turf

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 65; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; seat: left; toxicology performed; flight hours: 36 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 250° at 3 knots
- Visibility: 90 statute miles
- Lowest ceiling: none
- Temperature: 34 °F, dew point 12 °F
- Altimeter: 26.00 inHg
- Observed at: PUB, 25 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 19891124046569A](https://openairdocs.org/incident/19891124046569A), Nov 24, 1989: Amtrth THORPT18, Colorado City, CO, Destroyed, 1 fatal. Trailed blue smoke on climbout, stalled and hit ground near vertical impact. Prop damage indicates not under power.

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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