# NTSB WPR16LA023: Thorp T 18, N1488, Independence, OR, November 6, 2015 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: November 6, 2015, 15:30 local (23:30 UTC) - Place: Independence, OR - Coordinates: 44.836666, -123.200836 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=44.8367&lon=-123.2008&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Defining event: [Initial climb: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report November 28, 2016 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 92302 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR16LA023 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/92302/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=92302 - Page: https://openairdocs.org/ntsb/WPR16LA023 ## Probable cause A separation of the canopy mechanism during flight, which resulted in the pilot’s precautionary landing and the airplane’s subsequent collision with a fence post. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Doors: passenger/crew doors](https://openairdocs.org/ntsb-findings/01035210): Aircraft › Aircraft structures · Failure (probable cause); cases with it: [Thorp T-18, 1 case](https://openairdocs.org/ntsb-findings/01035210/cases.md?model=89510T7), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01035210/cases.md) - [Object/animal/substance: fence/fence post](https://openairdocs.org/ntsb-findings/03022047): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Thorp T-18, 1 case](https://openairdocs.org/ntsb-findings/03022047/cases.md?model=89510T7), [All aircraft, 313 cases](https://openairdocs.org/ntsb-findings/03022047/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Initial climb: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Thorp T-18, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=89510T7), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Thorp T-18, 3 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=89510T7), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot departed on a local flight; during initial climb, the canopy partially disconnected from the airplane and the airplane vibrated violently. The pilot made a precautionary landing in a field, and the right wing impacted a fence post. Postaccident examination revealed that the mechanism that allowed the canopy to move fore and aft and retained the aft portion of the canopy during flight separated at a weld, which resulted in airflow into the cockpit. The components were not made available for metallurgical examination and the failure mode could not be determined; however, it is possible that the separation was due to repeated loading on the canopy over time. According to the pilot and a representative of the airplane type club, the canopy design was unique to the accident airplane, and was likely the only one of its kind. ## Factual narrative On November 6, 2015, at 1530 Pacific standard time, an experimental Thorp T-18, N1488, was substantially damaged during a precautionary landing in a field near Independence State Airport, Independence, Oregon. The pilot was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. The private pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed and no flight plan was filed. In a phone interview following the accident, the pilot stated that the airplane was climbing after takeoff when the canopy partially disconnected from the airplane and the airplane violently vibrated. The pilot landed in a cow pasture and the right wing impacted a fence post during the landing roll. He further reported that the airplane was serial number 303 and his father had built the airplane. The airplane had an early canopy design that had been modified in later designs. The canopy ran on a track. On each side of the canopy there are two fiberglass rollers and the back was secured through a track. The rear track separated and allowed airflow underneath to lift up and vibrate the canopy. The pilot believed that the separation occurred due to repeated use over time. A Federal Aviation Administration (FAA) inspector examined the airplane following the accident. The canopy mechanism allowed the canopy to move fore and aft, as well as retain the aft portion of the canopy during flight. The rear portion of the mechanism separated at a weld. The Thorp T-18 type club was contacted regarding the canopy mechanism design. The mechanism was reported as a unique design and uncommon to the fleet. ## Aircraft - Registration: [N1488](https://openairdocs.org/aircraft/N1488), registered now, S/N 303 (OpenAirDocs) - Reported make and model: THORP T 18 (UNDESIGNAT) - Registry model: [Thorp T-18](https://openairdocs.org/model/thorp-t-18) (registry code 89510T8) (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: 303 - Year built: 1968 - Airframe hours: 1358 - Engines: Textron Lycoming O-320-B2A 160 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, March 1, 2015, 19 hours before - Departed: Independence, OR - Destination: Independence, OR - Airport: 7S5, Independence State - Equipment: Handheld GPS ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 68; injuries: none; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; seat: left; restraint: 3-point; flight hours: 618 total, 618 in this make and model, 18 in the last 90 days, 8 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 340° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 135 °F, dew point 115 °F - Altimeter: 30.31 inHg - Observed at: KSLE, 9 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 20151106020799A](https://openairdocs.org/incident/20151106020799A), Nov 6, 2015: Thorp T-18, Independence, OR, Substantial damage. On departure for second trip around the traffic pattern, canopy support beam failed causing the aft portion of the canopy to separate from the aircraft.… ## Docket (5 files) The files NTSB released with the investigation on September 22, 2016, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=92302. 7.4 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 5.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40444660&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Pilot Record of Conversation (item 2, .PDF, 131 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40444661&FileExtension=.PDF&FileName=Pilot%20Record%20of%20Conversation-Master.PDF - FAA Record of Conversation (item 3, .PDF, 120 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40444662&FileExtension=.PDF&FileName=FAA%20Record%20of%20Conversation-Master.PDF - Thorp T-18 Group Record of Conversation (item 4, .PDF, 122 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40444663&FileExtension=.PDF&FileName=Thorp%20T-18%20Group%20Record%20of%20Conversation-Master.PDF - WPR16LA023 Photos (item 5, .PDF, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40444664&FileExtension=.PDF&FileName=WPR16LA023%20Photos-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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.