# NTSB SEA94LA080: Unrein 80-P51D, N51PL, Scapp00se, OR, March 10, 1994

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: March 9, 1994, 17:00 local (Mar 10, 1994, 01:00 UTC)
- Place: Scapp00se, OR
- Coordinates: 45.79993, -122.970001 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=45.7999&lon=-122.9700&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report December 2, 1994
- Report: Approved by Office Director
- NTSB case key (mKey): 41893
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA94LA080
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/41893/pdf
- Page: https://openairdocs.org/ntsb/SEA94LA080

## Probable cause

THE INADVERTENT UNLOCKING OF THE TAILWHEEL LOCK. FACTORS INCLUDE THE MANUFACTURER'S INADEQUATE TAILWHEEL LOCK.

## Analysis

THE AIRCRAFT'S TAILWHEEL LOCKING MECHANISM INADVERTENTLY UNLOCKED EITHER DURING FLIGHT OR UPON TOUCHDOWN FOR THE FULL-STOP LANDING. WITH THE TAILWHEEL FREE TO PIVOT, THE PILOT LOST CONTROL OF THE AIRCRAFT DURING THE LANDING ROLL, AND THE MAIN LANDING GEAR COLLAPSED FROM OVERLOAD. THE PILOT/MANUFACTURER STATED THAT HE WOULD NOW REDESIGN THE MECHANISM SO THAT IT COULD NOT BE ACCIDENTALLY UNLOCKED.

## Factual narrative

On March 3, 1994, approximately 1700 Pacific standard time (PST), an experimental Unrein 80-P51D, N51PL, experienced a gear collapse during the landing roll at Scappoose Industrial Airpark, Scappoose, Oregon. The private pilot, who was the sole occupant of the aircraft, was not injured, but the aircraft sustained substantial damage. The personal pleasure flight, which departed Kelso-Longview Airport about 15 minutes earlier, was in visual meteorological conditions at the time of the accident. There was no flight plan filed, and there was no report of an ELT activation.

According to the pilot, the tailwheel locking mechanism accidently released either during flight or upon touchdown for a full-stop landing. With the tailwheel free to pivot, the pilot was unable to maintain directional control, and during the landing roll, the main gear was overloaded and collapsed.

The pilot advised the FAA inspector who responded to the accident that he would redesign the tailwheel locking system so that it could not inadvertently unlock.

## Sequence of events

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

- Airframe/component/system failure/malfunction, landing - roll
  - landing gear,tailwheel lock - unlocked (cause)
  - tailwheel lock - inadequate, manufacturer (contributing factor)
- Loss of control - on ground/water, landing - roll
- Gear collapsed, landing - roll
  - landing gear,main gear - overload

## Aircraft

- Registration: [N51PL](https://openairdocs.org/deregistered/N51PL-2015-05-08), registration cancelled 2015-05-08, S/N 001, built 1994 (OpenAirDocs)
- Reported make and model: UNREIN 80-P51D
- Registry model: [Unrein Paul PRODUCTMATCH 80 P51D](https://openairdocs.org/model/unrein-paul-productmatch-80-p51d) (registry code 05623FG) (OpenAirDocs)
- Registry engine: [Continental E185 series](https://openairdocs.org/engine/continental-e185-series) (registry code 17014, reciprocating) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: 001
- Airframe hours: 21
- Engines: CONTINENTAL E-185-11 205 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Registered owner: Unrein, Paul & Loretta
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Continuous airworthiness, January 25, 1994, 21 hours before
- Departed: KLS, KELSO, WA
- Airport: 1S4, Scappoose Industrial

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 51; private; airplane ratings: single-engine land; medical: class 3, valid medical--no waivers/lim.; seat: front; flight hours: 1,631 total, 21 in this make and model, 1,578 as pilot in command

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 25 statute miles
- Lowest ceiling: 4,500 ft overcast
- Temperature: 50 °F
- Altimeter: 30.00 inHg

## Other investigations on N51PL (1)

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

- [NTSB SEA02FA124](https://openairdocs.org/ntsb/SEA02FA124), Jul 6, 2002: Unrein Productmatch 80 P51D (N51PL), Battle Ground, WA, substantial damage. Probable cause: The pilot's failure to maintain the proper airspeed (80 mph) on final approach resulting in a bounced landing and a loss of control during an attempted go-around and ultimately the on ground…

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

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From OpenAirDocs.org, an independent open copy of NTSB and FAA data. The NTSB's own report is the official record of an investigation.