# NTSB WPR10LA429: Finney Thorp T-18, N467JF, Willcox, AZ, August 26, 2010

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Limited investigation · Final report
- Date: August 26, 2010, 09:20 local (16:20 UTC)
- Place: Willcox, AZ
- Coordinates: 32.245555, -109.894721 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=32.2456&lon=-109.8947&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Defining event: [Approach-VFR pattern downwind: Loss of control in flight](https://openairdocs.org/ntsb-events/240)
- Highest injury: Fatal
- Injuries: 2 fatal
- Status: Completed, report January 15, 2013
- Report: Approved by Office Director
- NTSB office: Western Pacific Region
- Parties: Federal Aviation Administration
- NTSB case key (mKey): 77099
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR10LA429
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/77099/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=77099
- Page: https://openairdocs.org/ntsb/WPR10LA429

## Probable cause

The pilot’s failure to maintain sufficient airspeed during a steep turn and at a low altitude in the traffic pattern, which resulted in an aerodynamic stall.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Performance/control parameters: airspeed](https://openairdocs.org/ntsb-findings/01062010): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Finney Thorp T-18, 1 case](https://openairdocs.org/ntsb-findings/01062010/cases.md?model=89510US), [All aircraft, 1,681 cases](https://openairdocs.org/ntsb-findings/01062010/cases.md)
- [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Finney Thorp T-18, 1 case](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=89510US), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Maneuvering-low-alt flying: Aerodynamic stall/spin](https://openairdocs.org/ntsb-events/241); cases with it: [Finney Thorp T-18, 1 case](https://openairdocs.org/ntsb-events/241/sequence.md?model=89510US), [All aircraft, 1,529 cases](https://openairdocs.org/ntsb-events/241/sequence.md)
- [Approach-VFR pattern downwind: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Finney Thorp T-18, 1 case](https://openairdocs.org/ntsb-events/240/sequence.md?model=89510US), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md)
- [Uncontrolled descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Finney Thorp T-18, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=89510US), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)

## Analysis

The airplane was observed in the traffic pattern, about 500 feet above ground level, when it made a steep left turn to enter the downwind leg. The turn continued as the airplane entered a left descending spiral until it impacted the ground in a nose-low attitude. Postaccident examination of the airframe and engine revealed no evidence of a mechanical malfunction or failure that would have precluded normal operation. The Pilot Operating Handbook for the airplane indicated that the airplane has an abrupt stall with a tendency to drop a wing, especially if the airplane is in an uncoordinated turn during the stall. There is very little warning preceding the stall. Stall recovery can be quickly affected by releasing back pressure on the stick; however, a secondary stall may occur if the stick is brought back abruptly after recovery without sufficient airspeed. It is likely that during the initial steep turn, the airplane entered an aerodynamic stall from which the pilot was unable to recover at the low altitude.

## Factual narrative

HISTORY OR FLIGHT On August 26, 2010, about 0920 mountain standard time, an experimental amateur-built Finney Thorp, T-18, N467JF, descended into terrain following an in-flight loss of control while entering the downwind leg of the traffic pattern at the Cochise County Airport (P33) Willcox, Arizona. The airplane was substantially damaged and the private pilot and passenger were fatally injured. The pilot/owner was operating the airplane under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed at the time of the personal cross country flight and no flight plan was filed. The flight originated from San Diego, California, at an undetermined time with an intended destination of P33. A witness, who was a Certified Flight Instructor (CFI) that was flying in an airplane about 500 feet above the accident airplane, reported observing the airplane entering the traffic pattern while flying about 500 feet above ground level (agl). The airplane was observed entering a steep left turn to the downwind leg for runway 03 and subsequently entered a left descending spiral until it impacted the ground in a nose low attitude. Another witness, located at the airport, observed the accident airplane’s engine power up and the airplane initiate a left turn around midfield. Personnel monitoring the airport’s common traffic advisory frequency (CTAF) reported hearing an unintelligible distress radio transmission around the time of the accident. WRECKAGE DOCUMENTATION A Federal Aviation Administration (FAA) inspector examined the airplane at the accident site. The airplane’s wings were bent and the forward portion of the fuselage was crushed aft. No evidence of a preimpact engine malfunction was noted. All of the flight control surfaces remained attached to their respective mounts with the exception of the right flap which was only attached by the outboard hinge and exhibited impact damage. A separation was found in the left aileron's push-pull control tube which separated it from the control stick bell crack. The left aileron push-pull control tube rod end bearing and jam nut where the separation was observed was sent to the National Transportation Safety Board (NTSB) Materials laboratory for further analysis. According to a Senior Metallurgist, optical examination of the fracture surface revealed that the separation of the aileron push-pull control tube rod end and jam nut was consistent with an overstress load. The Senior Metallurgist also observed no indication of progressive cracking or significant corrosion around the fracture surface. The surrounding structure housing the left aileron push-pull control tube rod end bearing and jam nut was buckled near the point of separation. An examination report is contained in the public docket for this accident. MEDICAL INFORMATION The Cochise County Office of the Medical Examiner reported that the cause of death to the pilot was a result of multiple blunt force injuries.Toxicological samples were sent to the Federal Aviation Administration, Civil Aeromedical Institute, Oklahoma City, Oklahoma. The examination was negative for all tested substances. ADDITIONAL INFORMATION The Pilot Operating Handbook for the T-18 indicated that the airplane has an abrupt stall with a tendency to drop a wing, especially if uncoordinated during the stall. There is very little warning preceding the stall. Stall recovery can be quickly effected by releasing back pressure on the stick, however a secondary stall may occur when the stick is brought back after recovery from the initial stall. If the stick is brought back too abruptly, without sufficient airspeed, a secondary stall will occur.

## Aircraft

- Registration: [N467JF](https://openairdocs.org/deregistered/N467JF-2013-04-22), registration cancelled 2013-04-22, S/N 467, built 1970 (OpenAirDocs)
- Reported make and model: FINNEY THORP T-18
- Registry model: [Finney Thorp T-18](https://openairdocs.org/model/finney-thorp-t-18) (registry code 89510US) (OpenAirDocs)
- Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: 467
- Engines: LYCOMING O-320 SERIES 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Glen Slagoske
- Registered owner: Sale Reported
- Airworthiness certificate: Special, Experimental (Special)
- Departed: MYF, San Diego, CA
- Destination: P33, Willcox, AZ
- Airport: P33, Cochise County, runway 03, 6,095 × 75 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 46; injuries: fatal; private; airplane ratings: multi-engine land, single-engine land; medical: class 2, with waivers/limitations; last flight review June 11, 2010; toxicology performed; flight hours: 500 total

## Weather

- Conditions: Visual (VMC), Day
- Wind: 45° at 5 knots, gusting 15
- Visibility: 10 statute miles
- Lowest ceiling: 10,000 ft broken
- Temperature: 81 °F

## 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 20100826042249A](https://openairdocs.org/incident/20100826042249A), Aug 26, 2010: Finney Thor T-18, Wilcox, AZ, Substantial damage, 2 fatal. On August 26, 2010, at approximately 09:20 PDT an experimental amateur built 1970 Finney thorp T-18, N467JF, serial number 467 was substantially damaged when…

## Other investigations on N467JF (1)

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.

- [NTSB LAX07CA009](https://openairdocs.org/ntsb/LAX07CA009), Oct 13, 2006: Finney Thorp T-18 (N467JF), San Diego, CA, substantial damage. Probable cause: the pilot's inadequate compensation for the crosswind conditions and failure to maintain directional control during landing.

## Docket (4 files)

The files NTSB released with the investigation on November 9, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=77099. 714 KB in all.

- Materials Laboratory 15 - Factual Report 12-080 (1 Embedded Image) (item 1, .PDF, 1 photo, 238 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40373020&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2012-080%20(1%20Embedded%20Image)-Master.PDF
- Witness Statement (item 2, .PDF, 60 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376596&FileExtension=.PDF&FileName=Witness%20Statement-Redacted.PDF
- Reports from Federal Agencies (item 3, .PDF, 302 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376691&FileExtension=.PDF&FileName=Reports%20from%20Federal%20Agencies-Redacted.PDF
- Toxicological Report (item 4, .PDF, 114 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40376677&FileExtension=.PDF&FileName=Toxicological%20Report-Master.PDF

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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