# NTSB CEN20LA259: Sopwith Type 9400, N5539, Van Alstyne, TX, July 3, 2020 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: July 3, 2020, 10:00 local (15:00 UTC) - Place: Van Alstyne, TX - Coordinates: 33.410507, -96.570556 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.4105&lon=-96.5706&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: Minor injuries - Injuries: 1 minor, 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA - NTSB case key (mKey): 101535 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN20LA259 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101535/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101535 - Page: https://openairdocs.org/ntsb/CEN20LA259 ## Probable cause An inflight loss of aileron control due to movement of a control connector. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Flight control system: control column section](https://openairdocs.org/ntsb-findings/01022701): Aircraft › Aircraft systems · Failure; cases with it: [Lankenau Kip F SOPWITH TYPE 9400, 1 case](https://openairdocs.org/ntsb-findings/01022701/cases.md?model=05638LQ), [All aircraft, 21 cases](https://openairdocs.org/ntsb-findings/01022701/cases.md) - [Flight control system: aileron control system](https://openairdocs.org/ntsb-findings/01022710): Aircraft › Aircraft systems · Malfunction; cases with it: [Lankenau Kip F SOPWITH TYPE 9400, 1 case](https://openairdocs.org/ntsb-findings/01022710/cases.md?model=05638LQ), [All aircraft, 45 cases](https://openairdocs.org/ntsb-findings/01022710/cases.md) - [Performance/control parameters: lateral/bank control](https://openairdocs.org/ntsb-findings/01062023): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible; cases with it: [Lankenau Kip F SOPWITH TYPE 9400, 1 case](https://openairdocs.org/ntsb-findings/01062023/cases.md?model=05638LQ), [All aircraft, 390 cases](https://openairdocs.org/ntsb-findings/01062023/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Lankenau Kip F SOPWITH TYPE 9400, 1 case](https://openairdocs.org/ntsb-events/333/sequence.md?model=05638LQ), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) - [Enroute: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Lankenau Kip F SOPWITH TYPE 9400, 1 case](https://openairdocs.org/ntsb-events/240/sequence.md?model=05638LQ), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Enroute: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Lankenau Kip F SOPWITH TYPE 9400, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=05638LQ), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis During a test flight the pilot moved the control stick fully to the right to roll out of a turn, but the airplane did not respond, and the pilot suspected a failure in the aileron controls. The airplane eventually rolled wings level and the pilot elected to perform an emergency landing to a corn field, during which the airplane hit a tree and descended into the field. The wings and fuselage were substantially damaged during impact. The pilot, who was also the builder of the airplane, examined the wreckage and determined that a rocking tube that connected the front cockpit control stick to the rear control stick had moved rearward about 1 inch. The aileron cables connected to a horn affixed to this tube. The rearward movement of the rocking tube was sufficient for the front part of the tube to come loose from its socket, which likely affected the control authority of the ailerons and resulted in the pilot’s inability to control the airplane. The pilot explained that there was nothing in the original design that prevented the rocking tube from sliding aft. ## Factual narrative On July 3, 2020, a Sopwith 9400, N5539, was substantially damaged when it was involved in an accident near Van Alstyne, Texas. The pilot received minor injuries and the passenger was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight. The airplane was a reproduction of a Sopwith 1 ½ Strutter built from original factory drawings. According to the pilot, who was also the builder of the airplane, this was the 23rd test flight of the airplane. The flight was scheduled to be a short flight to confirm flying and landing wire deflections, flight control synchronization while under air loading, and to perform an aerial reconnoiter for potential obstacles at the approach end of the runway. A second crewmember was also on board, responsible for monitoring cable deflections and vibrations and control surface positions during flight and was communicating with the ground crew via text message. The airplane performed normally through the first overflight of the airfield and a series of turns. However, when the pilot moved the control stick to the right to bring the wings level from a left turn, he noticed no resistance and the stick continued until it had reached its maximum travel. The pilot recognized this as a failure in the lower aileron circuit. Not knowing the exact location or cause of the failure, the pilot kept the control stick at its far right limit and waited for the effects of dihedral to slowly bring the wings back to level, while maintaining marginal control with back pressure on the elevator and right rudder. The airplane eventually settled wings level with a slight nose down attitude about 350 ft above ground level (agl). The pilot elected to perform an emergency landing in the cornfield in front of the airplane, during which the airplane impacted trees. The wooden-framed wing structures and fuselage were substantially damaged. The pilot reported that a rocking tube that connected the front cockpit control stick to the rear control stick had moved rearward about 1 inch. The aileron cables connected to a horn affixed to this tube. The rearward movement of the rocking tube was sufficient for the front part of the tube to come loose from its socket, which would have affected the control authority of the ailerons. The pilot explained that there was nothing in the original design that would prevent the rocking tube from sliding aft. ## Aircraft - Registration: [N5539](https://openairdocs.org/aircraft/N5539), registered now, S/N N5539, built 2019 (OpenAirDocs) - Reported make and model: SOPWITH Type 9400 - Registry model: [Lankenau Kip F SOPWITH TYPE 9400](https://openairdocs.org/model/lankenau-kip-f-sopwith-type-9400) (registry code 05638LQ) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 5539 - Year built: 2019 - Airframe hours: 19.8 - Engines: CAMS Gnome 100 horsepower reciprocating - Damage: Substantial damage - Flight: Flight test, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Destination: Same as departure - Airport: 66XS, Baylie ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 60; injuries: serious; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; last flight review July 9, 2019; seat: front; flight hours: 921 total, 20 in this make and model, 836 as pilot in command, 6 in the last 90 days, 3 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 2 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 80 °F - Observed at: TKI, 15 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 20200703018249A](https://openairdocs.org/incident/20200703018249A), Jul 3, 2020: Lankenau Kip F SOPWITH TYPE 9400, Van Alstyne, TX, Substantial damage. On July 3, 2020, at 0956 CDT, an experimental amateur built, Lankenau Kip F, sopwith type 9400, s/n 5539, while on a maintenance test flight was involved in an… ## Docket (5 files) The files NTSB released with the investigation on April 13, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101535. 7.7 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 4.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11914220&FileExtension=pdf&FileName=NTSB%20Form%206120.1%20completed_Redacted-Rel.pdf - Detailed pilot statement (item 2, PDF, 4 pages, 77 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11916371&FileExtension=pdf&FileName=Strutter%20accident%207-3-20-Rel.pdf - Pilot email examination results (item 3, PDF, 1 page, 108 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11914521&FileExtension=pdf&FileName=Pilot%20Email_Redacted-Rel.pdf - Photos (item 4, PDF, 3 pages, 3 photos, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=11916624&FileExtension=pdf&FileName=Photo%20Array%20CEN20LA259-Rel.pdf - Design drawings (item 5, PDF, 2 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12010765&FileExtension=pdf&FileName=Design%20Drawings_Redacted-Rel.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.