# NTSB MIA08LA174: Schweizer G-164B, N3633S, Clarksdale, MS, August 26, 2008 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 26, 2008, 13:15 local (18:15 UTC) - Place: Clarksdale, MS - Coordinates: 34.29, -90.510002 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.2900&lon=-90.5100&mi=10 - Phase of flight: [Taxi](https://openairdocs.org/ntsb-phases/250) (OpenAirDocs' grouping) - Defining event: [Taxi-from runway: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report September 30, 2009 - Report: Approved by Office Director - Parties: FAA/FSDO - NTSB case key (mKey): 68806 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA08LA174 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/68806/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=68806 - Page: https://openairdocs.org/ntsb/MIA08LA174 ## Probable cause The mechanic’s failure to torque check the axle-to-spring gear attachment bolts per the manufacturer's Annual/100-Hour Airframe Inspection Checklist, resulting in fatigue failure of the bolts. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Inspection](https://openairdocs.org/ntsb-findings/02061500): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Schweizer G-164B, 1 case](https://openairdocs.org/ntsb-findings/02061500/cases.md?model=8059055), [All aircraft, 29 cases](https://openairdocs.org/ntsb-findings/02061500/cases.md) - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Fatigue/wear/corrosion; cases with it: [Schweizer G-164B, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=8059055), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Taxi-from runway: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Schweizer G-164B, 3 cases](https://openairdocs.org/ntsb-events/330/sequence.md?model=8059055), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Taxi-from runway: Landing gear collapse](https://openairdocs.org/ntsb-events/094); cases with it: [Schweizer G-164B, 3 cases](https://openairdocs.org/ntsb-events/094/sequence.md?model=8059055), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis While applying the left brake during taxi after landing, the pilot first heard a "loud pop from the left gear" and during further brake application, the left axle and wheel assembly separated. Two MS20008H22 bolts and one AN509-616-35 screw that secure the axle to the spring leg were fractured. The failure mode of the bolts was due to fatigue, and was typical of bolts that are insufficiently torqued. The mechanic who last inspected the airplane used his own checklist and did not torque check the bolts and screw, which is required by the manufacturer's Annual/100-Hour Airframe Inspection Checklist. ## Factual narrative On August 26, 2008, about 1315 central daylight time, a Schweizer Aircraft Corporation G-164B, N3633S, registered to Howard Flying Service, operated by Howard Flying Service, Inc., experienced separation of the left main landing gear axle and wheel assembly while taxiing after landing at Fletcher Field Airport (CKM), Clarksdale, Mississippi. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 Code of Federal Regulations (CFR) Part 137 aerial application flight from CKM. The airplane was substantially damaged and the certificated commercial pilot was not injured. The flight originated about 1243, from CKM. The pilot stated that while taxiing after landing, he applied the left brake and heard a "loud pop from the left gear." Further application of the left brake was required to keep the aircraft going straight and when he applied the left brake for the third time, the left axle and wheel assembly separated. The airplane then veered to the left and nosed up momentarily before the tail wheel contacted the ground. Damage to the lower left wing spar was noted. Examination of the airplane by a Federal Aviation Administration (FAA) airworthiness inspector revealed that two MS20008H22 bolts and one AN509-616-35 screw that secures the axle to the left spring leg gear were fractured. The bolts and screw were retained for further examination by the National Transportation Safety Board (Safety Board's) Materials Laboratory. Examination of the fractured bolts and screw by the Safety Board's Materials Laboratory revealed the fracture surface of the screw was damaged which precluded determination of failure mode; however, the threads were deformed. Examination of both bolts revealed ratchet marks consistent with multiple fatigue crack initiation sites. The airplane was manufactured in 1987, and at the time of the accident had accrued 10,282.0 hours. The last annual inspection was performed on March 4, 2008, at airplane total time 9,945.0 hours. The mechanic who performed the last annual inspection stated that he used his own checklist and did not torque check the axle attachment bolts as specified in the manufacturer's Annual/100 Hour Airframe Inspection Check List. ## Aircraft - Registration: [N3633S](https://openairdocs.org/aircraft/N3633S), registered now, S/N 778B, built 1986 (OpenAirDocs) - Reported make and model: SCHWEIZER AIRCRAFT CORP G-164B - Registry model: [Schweizer G-164B](https://openairdocs.org/model/schweizer-g-164b) (registry code 8059055) (OpenAirDocs) - Registry engine: [Pratt & Whitney R1340 series](https://openairdocs.org/engine/pratt-whitney-r1340-series) (registry code 52016, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 778B - Airframe hours: 10282 - Engines: P&W PT6A-27/28 680 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Howard Flying Service - Registered owner: Howard Flying Service - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, March 4, 2008, 337 hours before - Departed: CKM, Clarksdale, MS - Destination: CKM - Airport: CKM, Fletcher Field Airport ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 43; injuries: none; commercial; airplane ratings: single-engine land; medical: class 2, without waivers/limitations; last flight review November 29, 2007; seat: center; flight hours: 10,557 total, 930 in this make and model, 10,498 as pilot in command, 200 in the last 90 days, 50 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 330° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: 4,200 ft broken - Temperature: 81 °F, dew point 70 °F - Altimeter: 29.80 inHg - Observed at: UTA, 25 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 20080826843969A](https://openairdocs.org/incident/20080826843969A), Aug 26, 2008: Scwzer G164B, Clarksdale, MS, Minor damage. (-23) During taxi left main landing gear axle bolts broke. ## Other investigations on N3633S (1) 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. - [NTSB ERA13LA312](https://openairdocs.org/ntsb/ERA13LA312), Jun 29, 2013: Schweizer G-164B (N3633S), Jackson, TN, substantial damage. Probable cause: A failure of the right main landing gear wheel rim during the landing roll, resulting in a loss of control and a subsequent collapse of the right main landing gear. ## Docket (9 files) The files NTSB released with the investigation on June 22, 2009, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=68806. 18.2 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 362 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40307330&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Materials Laboratory 15 - Factual Report 09-031 (item 2, .PDF, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40312804&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2009-031-Master.PDF - Weather Reports and Records (item 3, .PDF, 10 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40307331&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records-Master.PDF - Record of NTSB Conversation (item 4, .PDF, 49 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40307430&FileExtension=.PDF&FileName=Record%20of%20NTSB%20Conversation-Redacted.PDF - Record of FAA Conversation (item 5, .PDF, 20 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40307431&FileExtension=.PDF&FileName=Record%20of%20FAA%20Conversation-Master.PDF - Excerpt from Airframe Logbook (item 6, .PDF, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40307332&FileExtension=.PDF&FileName=Excerpt%20from%20Airframe%20Logbook-Redacted.PDF - Excerpts from Maintenance Manual (item 7, .PDF, 9.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40307333&FileExtension=.PDF&FileName=Excerpts%20from%20Maintenance%20Manual-Master.PDF - Excerpts from Illustrated Parts Catalog (item 8, .PDF, 4.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40307334&FileExtension=.PDF&FileName=Excerpts%20from%20Illustrated%20Parts%20Catalog-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 9, .PDF, 68 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40313729&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.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.