# NTSB ERA11IA172: Mitsubishi MU-2B-20, N52CD, Walterboro, SC, January 16, 2011 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: January 16, 2011, 15:00 local (20:00 UTC) - Place: Walterboro, SC - Coordinates: 32.920833, -80.641113 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=32.9208&lon=-80.6411&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: 2 uninjured - Status: Completed, report February 23, 2012 - Report: Approved by Office Director - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO, Mitsubishi Heavy Industries America, Inc. - NTSB case key (mKey): 78474 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA11IA172 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/78474/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=78474 - Page: https://openairdocs.org/ntsb/ERA11IA172 ## Probable cause The inadequate inspection and rigging of the nose landing gear downlock mechanism by maintenance personnel, which resulted in the failure of a bolt and the subsequent collapse of the nose gear during the landing roll. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Maintenance/inspections: scheduled maint checks](https://openairdocs.org/ntsb-findings/01010520): Aircraft › Aircraft handling/service · Inadequate inspection (probable cause); cases with it: [Mitsubishi MU-2B-20, 1 case](https://openairdocs.org/ntsb-findings/01010520/cases.md?model=5780407), [All aircraft, 76 cases](https://openairdocs.org/ntsb-findings/01010520/cases.md) - [Landing gear system: nose/tail landing gear](https://openairdocs.org/ntsb-findings/01023220): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Mitsubishi MU-2B-20, 1 case](https://openairdocs.org/ntsb-findings/01023220/cases.md?model=5780407), [All aircraft, 185 cases](https://openairdocs.org/ntsb-findings/01023220/cases.md) - [Action: lack of action](https://openairdocs.org/ntsb-findings/02041030): Personnel issues › Action/decision · Maintenance personnel (probable cause); cases with it: [Mitsubishi MU-2B-20, 1 case](https://openairdocs.org/ntsb-findings/02041030/cases.md?model=5780407), [All aircraft, 792 cases](https://openairdocs.org/ntsb-findings/02041030/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Aircraft inspection event](https://openairdocs.org/ntsb-events/050); cases with it: [Mitsubishi MU-2B-20, 1 case](https://openairdocs.org/ntsb-events/050/sequence.md?model=5780407), [All aircraft, 229 cases](https://openairdocs.org/ntsb-events/050/sequence.md) - [Landing-landing roll: Landing gear collapse](https://openairdocs.org/ntsb-events/094) (defining event); cases with it: [Mitsubishi MU-2B-20, 1 case](https://openairdocs.org/ntsb-events/094/sequence.md?model=5780407), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) ## Analysis The pilot reported hearing a “pop” sound from the nose gear area when the gear was extended for the landing. Toward the end of the landing roll, the nose gear collapsed. A postaccident examination of the nose gear revealed that the bolt that holds the downlock drag brace joint link to the airframe structure had fractured. A metallurgical examination revealed that the bolt failed in reverse bending fatigue, which is associated with the bolt having insufficient clamping pressure (looseness). The airplane’s last required inspection was about 70 flight hours and 40 gear cycles before the nose gear collapsing, and the nose gear downlock system rigging should have been inspected at that time. ## Factual narrative On January 16, 2011, at 1500 eastern standard time, a Mitsubishi, MU-2B-20, N52CD, owned by Hayes Landing, LLC and operated by an individual, had the nose landing gear collapse during landing at the Lowcountry Regional Airport (RBW), Walterboro, South Carolina. The pilot and passenger were not injured and the airplane incurred minor damage. Visual meteorological conditions prevailed and an instrument flight plan was filed for the personal flight, operated under the provisions of Title 14 Code of Federal Regulations Part 91. The flight departed from the Northeast Regional Airport (EDE), Edenton, North Carolina, earlier that day, about 1330. The pilot stated that the flight was uneventful. During the gear extension, on approach to the airport, he heard a “pop” as the nose gear lowered. During the landing roll the nose gear collapsed, resulting in minor damage to the nose gear doors and the skin behind the nose gear area. Maintenance personnel discovered the attaching bolt for the drag strut for the down lock mechanism assembly fractured. The bolt had an estimated in service time of 500 hours with an estimated 290 gear cycles. The fractured bolt was retained for further examination. The airplane’s last one year/100 hr/200 hour inspection was performed on September 14, 2010, at airframe total time of 8,053 hours. At the time of the accident the airframe had accumulated a total time of 8,124 hours. The National Transportation Safety Board Materials Laboratory conducted a metallurgical examination on the fractured bolt. The examination revealed the bolt failed in reverse bending fatigue. The bolt holds the down lock drag brace joint link to the airframe structure. The airplane’s manufacturer maintenance manual calls for and indicates when to check for proper rigging of the nose gear down lock system. Manufacturer Service Bulletin (SB) No. 188, dated July 13, 1981, which was developed due to several incidents were the improper adjustment of the down lock mechanism led to the failure of the nose landing gear. The SB requires inspection of the mechanism for proper adjustment (rigging). As a result of this incident the manufacturer published a Service News letter, dated September 5, 2011, outlining the importance of proper rigging of the down lock mechanism, making reference to the SB No. 188, and informing maintenance personnel and operator were to obtain the correct rigging tools. ## Aircraft - Registration: [N52CD](https://openairdocs.org/deregistered/N52CD-2014-07-17), registration cancelled 2014-07-17, S/N 174, built 1969 (OpenAirDocs) - Reported make and model: MITSUBISHI MU-2B-20 - Registry model: [Mitsubishi MU-2B-20](https://openairdocs.org/model/mitsubishi-mu-2b-20) (registry code 5780407) (OpenAirDocs) - Registry engine: [AiResearch TPE331 series](https://openairdocs.org/engine/airesearch-tpe331-series) (registry code 01514, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 174 - Airframe hours: 8125 - Engines: AIRESEARCH TPE331 SERIES 904 horsepower turbo prop; AIRESEARCH TPE331 SERIES 904 horsepower turbo prop - Damage: Minor damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Utility - Last inspection: 100 hour, September 14, 2010, 71 hours before - Departed: EDE, Edenton, NC - Destination: RBW, Watertown, SC - Flight plan: IFR - Airport: RBW, Lowcounty Regional Airport, runway 23, 6,002 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 49; injuries: none; private; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; seat: left; flight hours: 2,190 total, 425 in this make and model, 2,150 as pilot in command, 8 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: 240° at 6 knots - Visibility: 10 statute miles - Temperature: 68 °F, dew point 61 °F - Altimeter: 29.98 inHg - Observed at: RBW ## 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 20110116004219I](https://openairdocs.org/incident/20110116004219I), Jan 16, 2011: Mitsubishi MU-2B-20, Walterboro, SC, Minor damage. The aircraft landed on runway 23 at Lowcountry Regional Airport (rbw) in Walterboro, SC on January 16, 2011 at 1500 hours local time. On rollout the pilot… ## Docket (10 files) The files NTSB released with the investigation on December 19, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=78474. 8.0 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 484 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40359166&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Miscellaneous:Excerpts From the Airplane's Maintenance Records. (item 2, .PDF, 170 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40359169&FileExtension=.PDF&FileName=Miscellaneous%3AExcerpts%20From%20the%20Airplane%27s%20Maintenance%20Records.-Redacted.PDF - Miscellaneous: Excerpts From the Airplane's IPC and Landing Gear Maintnenance Inspection Details. (item 3, .PDF, 280 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40359168&FileExtension=.PDF&FileName=Miscellaneous%3A%20Excerpts%20From%20the%20Airplane%27s%20IPC%20and%20Landing%20Gear%20Maintnenance%20Inspection%20Details.-Master.PDF - Miscellaneous: Excerpts from the Airplane's Maintenance Manual (item 4, .PDF, 224 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40359219&FileExtension=.PDF&FileName=Miscellaneous%3A%20Excerpts%20from%20the%20Airplane%27s%20Maintenance%20Manual-Master.PDF - Miscellaneous: MU2 , Service Bulletin No. 188, Dated: July 13, 1981. (item 5, .PDF, 5.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40359171&FileExtension=.PDF&FileName=Miscellaneous%3A%20MU2%20,%20Service%20Bulletin%20No.%20188,%20Dated%3A%20July%2013,%201981.-Master.PDF - Materials Laboratory 15 - Factual Report 11-039 (with 4 embedded photos) (item 6, .PDF, 382 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40347026&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2011-039%20(with%204%20embedded%20photos)-Master.PDF - Other Pertinent Forms and Reports:Service Letter for the MU-2B Airplane. (item 7, .PDF, 181 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40359170&FileExtension=.PDF&FileName=Other%20Pertinent%20Forms%20and%20Reports%3AService%20Letter%20for%20the%20MU-2B%20Airplane.-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 8, .PDF, 78 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40359174&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Evidence Control Form (item 9, .PDF, 61 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40359272&FileExtension=.PDF&FileName=Evidence%20Control%20Form-Master.PDF - Photo 1) View of Damage to Lower Skin Fuselage Area Behind Nose Landing Gear. Photo Provided by Federal Avaiton Administration. (item 10, .PDF, 906 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40359173&FileExtension=.PDF&FileName=Photo%201)%20View%20of%20Damage%20to%20Lower%20Skin%20Fuselage%20Area%20Behind%20Nose%20Landing%20Gear.%20Photo%20Provided%20by%20Federal%20Avaiton%20Administration.-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.