# NTSB ERA16LA260: Sorensen Danny Pitts S1 S, N4714H, Somerville, TN, July 15, 2016 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 14, 2016, 19:30 local (Jul 15, 2016, 00:30 UTC) - Place: Somerville, TN - Coordinates: 35.207778, -89.394447 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.2078&lon=-89.3944&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report October 17, 2017 - Report: Approved by Office Director - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO - NTSB case key (mKey): 93620 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA16LA260 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/93620/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=93620 - Page: https://openairdocs.org/ntsb/ERA16LA260 ## Probable cause The failure of the left landing gear leg due to fatigue, which resulted in a ground loop during landing. Contributing to the accident was the airplane builder's installation of a custom-built landing gear rather than the landing gear included with the airplane kit. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [Sorensen Danny PITTS S1-S, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=72206AZ), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Sorensen Danny PITTS S1-S, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=72206AZ), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) - [Maintenance: fabrication](https://openairdocs.org/ntsb-findings/02062025): Personnel issues › Task performance · Owner/builder (probable cause); cases with it: [Sorensen Danny PITTS S1-S, 1 case](https://openairdocs.org/ntsb-findings/02062025/cases.md?model=72206AZ), [All aircraft, 30 cases](https://openairdocs.org/ntsb-findings/02062025/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Owner/builder (probable cause); cases with it: [Sorensen Danny PITTS S1-S, 1 case](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=72206AZ), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) (defining event); cases with it: [Sorensen Danny PITTS S1-S, 1 case](https://openairdocs.org/ntsb-events/094/sequence.md?model=72206AZ), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) - [Landing-landing roll: Loss of control on ground](https://openairdocs.org/ntsb-events/230); cases with it: [Sorensen Danny PITTS S1-S, 1 case](https://openairdocs.org/ntsb-events/230/sequence.md?model=72206AZ), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Landing-landing roll: Abnormal runway contact](https://openairdocs.org/ntsb-events/090); cases with it: [Sorensen Danny PITTS S1-S, 1 case](https://openairdocs.org/ntsb-events/090/sequence.md?model=72206AZ), [All aircraft, 1,506 cases](https://openairdocs.org/ntsb-events/090/sequence.md) ## Analysis The private pilot was conducting a cross-country, personal flight in the experimental, amateur-built, tailwheel-equipped airplane. The pilot reported that, while slowing the airplane after a normal three-point landing in a calm wind, the airplane began swerving. The airplane then departed the right side of the runway and ground looped. Examination of the wreckage revealed that the left landing gear leg had separated. Metallurgical examination of the fractured landing gear leg surface revealed a small thumbnail-like fatigue region, followed by an overstress region. A previous owner had assembled the airplane from a kit about 32 years before the accident, and it had accumulated about 875 total hours of operation. The builder did not use the stock bungie landing gear that were included with the kit. Rather, to reduce drag, he designed and constructed his own round, tapered rod landing gear. It is likely that the homemade, custom-built landing gear leg could not support the same loading as the stock bungie landing gear, which resulted in fatigue over a period of time and the gear leg's subsequent failure. ## Factual narrative On July 14, 2016, about 1930 central daylight time, an experimental amateur-built Pitts S1-S, N4714H, was substantially damaged while landing at Fayette County Airport (FYE), Somerville, Tennessee. The private pilot was not injured. The airplane was registered to and operated by the private pilot as a personal flight conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the flight that originated from Wolf River Airport (54M), Rossville, Tennessee, about 1845.The pilot reported that after a normal three-point landing in a calm wind, the airplane began swerving as it slowed. The airplane then departed the right side of the runway and ground-looped, which resulted in substantial damage to the lower left wing. Examination of the wreckage by a Federal Aviation Administration (FAA) inspector revealed that the left landing gear leg had separated and exhibited corrosion. The left landing gear leg was retained and forwarded to the National Transportation Safety Board Materials Laboratory for further examination. Metallurgical examination of the fracture surface revealed a small thumbnail like fatigue region followed by an overstress region. The single-seat, bi-wing, tailwheel-equipped airplane, serial number DS-1, was assembled from a kit in 1984 and issued an FAA experimental airworthiness certificate. Its most recent condition inspection was completed on April 23, 2016. At that time, the airframe had accumulated 865 total hours of operation. It had flown an additional 11 hours from the time of the last inspection, until the accident. The FAA inspector that examined the wreckage further stated that a previous owner built the airplane and did not use the stock bungie landing gear that was included with the kit. Rather, to reduce drag, he designed and constructed his own round tapered rod landing gear. ## Aircraft - Registration: [N4714H](https://openairdocs.org/deregistered/N4714H-2019-09-06), registration cancelled 2019-09-06, S/N DS-1, built 1984 (OpenAirDocs) - Reported make and model: SORENSEN DANNY PITTS S1 S (NO SERIES) - Registry model: [Sorensen Danny PITTS S1-S](https://openairdocs.org/model/sorensen-danny-pitts-s1-s) (registry code 72206AZ) (OpenAirDocs) - Registry engine: [Lycoming O&VO-360 series](https://openairdocs.org/engine/lycoming-o-vo-360-series) (registry code 41514, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: DS-1 - Year built: 1984 - Airframe hours: 865 - Engines: Lycoming O-360 180 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, April 23, 2016, 11 hours before - Departed: 54M, Rossville, TN - Destination: FYE, Somerville, TN - Airport: FYE, Fayette County Airport, runway 1, 5,000 × 75 ft, asphalt - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 56; injuries: none; private; airplane ratings: single-engine land, multi-engine land; medical: class 3, with waivers/limitations; last flight review July 14, 2014; seat: single; restraint: 5-point; flight hours: 2,700 total, 100 in this make and model, 2,700 as pilot in command, 15 in the last 90 days, 5 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 250° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Altimeter: 29.98 inHg - Observed at: OLV, 20 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 20160714010949A](https://openairdocs.org/incident/20160714010949A), Jul 14, 2016: Sorensen Danny PITTS S1-S, Somerville, TN, Substantial damage. On July 14, 2016 at approximately 1930 local time, aircraft N4714H an experimental/amateur-built pitts S1-S landed on runway 1 at fayette county airport(kfye).… ## Docket (6 files) The files NTSB released with the investigation on August 17, 2017, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=93620. 2.3 MB in all. - Materials Laboratory Factual Report (item 1, .PDF, 4 photos, 586 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40455373&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 2, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40455374&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Interview Summary (item 3, .PDF, 108 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40455375&FileExtension=.PDF&FileName=Interview%20Summary-Master.PDF - Weather Report (item 4, .PDF, 116 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40455376&FileExtension=.PDF&FileName=Weather%20Report-Master.PDF - Evidence Control Form (item 5, .PDF, 139 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40455377&FileExtension=.PDF&FileName=Evidence%20Control%20Form-Master.PDF - Photo (Courtesy of FAA) (item 6, .PDF, 1 photo, 273 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40455378&FileExtension=.PDF&FileName=Photo%20(Courtesy%20of%20FAA)-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.