# NTSB ERA22LA296: American Champion 8KCAB, N721SD, Knoxville, TN, June 28, 2022 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 4 · Limited · Final report - Date: June 28, 2022, 10:30 local (14:30 UTC) - Place: Knoxville, TN - Coordinates: 35.963454, -83.875098 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.9635&lon=-83.8751&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 4 - Basic report with no Prelim publish - NTSB office: Eastern Region Aviation - Parties: FAA-FSDO - NTSB case key (mKey): 105404 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA22LA296 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/105404/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=105404 - Page: https://openairdocs.org/ntsb/ERA22LA296 ## Probable cause The inadequate maintenance of the left main landing gear through bolt, which resulted in a left main landing gear collapse and subsequent runway excursion during landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: main landing gear attach sec](https://openairdocs.org/ntsb-findings/01023211): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [All aircraft, 66 cases](https://openairdocs.org/ntsb-findings/01023211/cases.md) - [Maintenance: scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [All aircraft, 320 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing: Landing gear collapse](https://openairdocs.org/ntsb-events/094); cases with it: [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis After performing maneuvers in the local area, the pilot receiving instruction and the flight instructor returned to the departure airport and performed two practice landings. During the third landing, the flight instructor heard a “bang” noise and the airplane veered left away from the runway centerline. The airplane came to rest in the grass next to the runway and the airplane’s fuselage and rudder were substantially damaged. A Federal Aviation Administration inspector examined the airplane after the accident. The airplane’s left main landing gear had collapsed and the inspector found that the left main landing gear through bolt was fractured. The inspector further reported that the airplane’s most recent annual inspection had been completed more than 22 months before the accident. Additionally, the airframe manufacturer’s maintenance manual required that the through bolt be removed and inspected at every 100 hour/annual inspection and replaced as necessary, in addition to a mandatory replacement every 500 hours. The airplane’s maintenance records did not show when the last though bolt change had occurred. Based on this information, it is likely that the landing gear collapsed due to a failure of the left main landing gear through bolt, and that the through bolt had likely not been maintained in accordance with the airframe manufacturer’s requirements. ## Aircraft - Registration: N721SD (not matched to a registry record) - Reported make and model: AMERICAN CHAMPION AIRCRAFT 8KCAB - Category: Airplane - Serial number: 722-93 - Year built: 1993 - Airframe hours: 2318 - Engines: Lycoming IO-360 180 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Super D Aviation Training Co LLC - Registered owner: Super D Aviation Training Co LLC - Airworthiness certificate: Standard, Aerobatic; Standard, Normal - Last inspection: Annual, August 1, 2020, 170 hours before - Airport: DKX, Knoxville Downtown Island, runway 8, 3,499 × 75 ft, asphalt - Equipment: Stall warning system, ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 20; injuries: none; private; airplane ratings: single-engine land; medical: class 2, without waivers/limitations; last flight review August 19, 2021; seat: front; flight hours: 63.1 total, 2.7 in this make and model, 16.8 as pilot in command, 5.9 in the last 90 days, 2.7 in the last 30 days - Flight instructor; age 73; injuries: none; military, commercial, airline transport, flight instructor, flight engineer; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review February 2, 2022; seat: rear; restraint: 3-point; flight hours: 25,000 total, 1,000 in this make and model, 20,000 as pilot in command, 200 in the last 90 days, 80 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 75 °F, dew point 59 °F - Altimeter: 30.21 inHg - Observed at: DKX - METAR: METAR KDKX 281415Z AUTO VRB04KT 10SM CLR 24/15 A3021 RMK A01 ## Docket (5 files) The files NTSB released with the investigation on June 23, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=105404. 8.6 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 - student pilot (item 1, PDF, 9 pages, 2.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14457210&FileExtension=pdf&FileName=Knoxville%206120_Redacted-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 - flight instructor (item 2, PDF, 11 pages, 4.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15619402&FileExtension=pdf&FileName=6120%20-%20N721SD_JBurt_Redacted-Rel.pdf - Witness statement (item 3, PDF, 1 page, 88 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15300521&FileExtension=pdf&FileName=Witness%20Statement_GS_Redacted-Rel.pdf - Memorandum for record a�� FAA inspector's statement (item 4, PDF, 1 page, 66 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15619166&FileExtension=pdf&FileName=MOR%20FAA%20Inspector%20Statement-Rel.pdf - Photographs (item 5, PDF, 7 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15610745&FileExtension=pdf&FileName=Photo%20Array%20ERA22LA296-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.