# NTSB ERA22LA171: Cessna 172, N8431U, Sparta, TN, March 27, 2022 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: March 27, 2022, 11:30 local (16:30 UTC) - Place: Sparta, TN · runway 4 - Coordinates: 36.055915, -85.530775 - Nearby events: https://openairdocs.org/map.md?lat=36.0559&lon=-85.5308&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO - NTSB case key (mKey): 104833 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA22LA171 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/104833/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=104833 - Page: https://openairdocs.org/ntsb/ERA22LA171 ## Probable cause Maintenance personnel’s failure to properly affix left main landing gear components, which led to the failure of the left main landing gear during the accident flight. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Aircraft](https://openairdocs.org/ntsb-findings/01030000): Aircraft › Aircraft structures · Failure; cases with it: [Cessna 172F, 1 case](https://openairdocs.org/ntsb-findings/01030000/cases.md?model=2072414), [All aircraft, 72 cases](https://openairdocs.org/ntsb-findings/01030000/cases.md) - [Maintenance: repair](https://openairdocs.org/ntsb-findings/02062015): Personnel issues › Task performance · Maintenance personnel; cases with it: [Cessna 172F, 1 case](https://openairdocs.org/ntsb-findings/02062015/cases.md?model=2072414), [All aircraft, 99 cases](https://openairdocs.org/ntsb-findings/02062015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-flare/touchdown: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) (defining event); cases with it: [Cessna 172F, 1 case](https://openairdocs.org/ntsb-events/337/sequence.md?model=2072414), [All aircraft, 290 cases](https://openairdocs.org/ntsb-events/337/sequence.md) ## Analysis During a touch-and-go landing, the student pilot and flight instructor heard a pop sound as they touched down. The student pilot initiated a go-around and then informed the instructor that the left main landing gear (LMLG) had separated from the airplane. They flew for about 2.5 hours to reduce the airplane’s fuel load before attempting to land with the fractured LMLG. The landing was uneventful and the airplane came to a stop on the runway. According to the instructor the LMLG struck the horizontal stabilizer when it separated, resulting in substantial damage. Examination of the left main landing gear spring strut revealed that the step bracket was tack welded onto the spring strut. According to the airplane manufacturer, step brackets can only be affixed to the spring strut using an approved epoxy adhesive; welding on the spring strut is not permitted. This improper maintenance resulted in a fatigue crack and the failure of the gear during the accident flight due to overstress. ## Factual narrative On March 27, 2022, about 1130 central daylight time, a Cessna 172, N8431U, was substantially damaged when it was involved in an accident near Sparta, Tennessee. The student pilot and flight instructor were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. According to the instructor, the student pilot was practicing touch-and-go landings. They heard a “pop” sound as the airplane touched down. The student pilot initiated a go-around and then informed the instructor that the left main landing gear (LMLG) had separated from the airplane. They flew for about 2.5 hours to reduce the airplane’s fuel load before attempting to land with the fractured LMLG. The landing was uneventful, and the airplane came to a stop on the runway. According to the instructor, the LMLG struck the horizontal stabilizer when it separated, resulting in substantial damage. The LMLG spring strut was examined by the National Transportation Safety Board Materials Laboratory. The LMLG spring strut fractured where the step bracket was affixed to the spring strut. The step bracket was tack welded to the spring strut. No epoxy adhesive was present on the faying surfaces of the step bracket or spring strut. According to the Cessna service manual, step brackets can only be affixed to the spring strut using an approved epoxy adhesive on abrasively blasted surfaces; welding on the spring strut is not permitted. The Materials Laboratory examination also found a fatigue crack that initiated at a tack weld between the step bracket and the spring strut and propagated to a length of about 0.2 inches. The fatigue crack led to an overstress fracture during the accident flight. ## Aircraft - Registration: [N8431U](https://openairdocs.org/aircraft/N8431U), registered now, S/N 17252331, built 1964 (OpenAirDocs) - Reported make and model: CESSNA 172 (F) - Registry model: [Cessna 172F](https://openairdocs.org/model/cessna-172f) (registry code 2072414) (OpenAirDocs) - Registry engine: [Continental 0-300 series](https://openairdocs.org/engine/continental-0-300-series) (registry code 17022, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 17252331 - Year built: 1964 - Engines: Continental O-300 145 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Airworthiness certificate: Standard, Utility; Standard, Normal - Last inspection: Annual, April 17, 2021 - Destination: Same as departure - Airport: SRB, Upper Cumberland Regional Airport, runway 4, 6,704 × 100 ft, asphalt - Equipment: Unknown ## Flight crew As NTSB recorded them. NTSB leaves out names. - Flight instructor; age 40; injuries: none; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review May 9, 2020; seat: right; restraint: 3-point; flight hours: 1,387 total, 72 in this make and model, 1,308 as pilot in command, 163 in the last 90 days, 62 in the last 30 days - Student pilot; age 33; injuries: none; student; medical: class 3, without waivers/limitations; seat: left; restraint: 3-point; flight hours: 30 total, 30 in this make and model, 1 as pilot in command, 18 in the last 90 days, 7 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 310° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 43 °F, dew point 19 °F - Altimeter: 30.15 inHg - Observed at: SRB - METAR: KSRB 271635Z AUTO 31007KT 270V020 10SM CLR 06/M07 A3015 RMK A01 ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Incident 20220327011869I](https://openairdocs.org/incident/20220327011869I), Mar 27, 2022: Cessna 172F, Sparta, TN, Minor damage. During a training flight the CFI and his student were retured to their home airport. (Upper Cumberland Regional Airport) (srb) During the inital touchdown they… ## Docket (5 files) The files NTSB released with the investigation on November 8, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=104833. 22.5 MB in all. - Materials laboratory factual report 22-104 (item 1, PDF, 15 pages, 11 photos, 7.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14979870&FileExtension=pdf&FileName=Materials%20Laboratory%20Factual%20Report%2022-104-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 11 pages, 12.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15220073&FileExtension=pdf&FileName=NTSB%20Form%206120_Redacted-Rel.pdf - Maintenance manual excerpt (item 3, PDF, 6 pages, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15220287&FileExtension=pdf&FileName=100%20Series%20MM%20landing%20gear%20pg%201-6-Rel.pdf - Evidence control form (item 4, PDF, 1 page, 137 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15220710&FileExtension=pdf&FileName=Evidence-Control-Form-Rel.pdf - Photos (item 5, PDF, 3 pages, 493 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15599449&FileExtension=pdf&FileName=Photos-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.