# NTSB CEN09LA571: Messerschmitt-Boelkow-Blohm BO-105S, N131EH, Thibodaux, LA, September 6, 2009 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: September 6, 2009, 14:00 local (19:00 UTC) - Place: Thibodaux, LA - Coordinates: 29.747777, -90.832778 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=29.7478&lon=-90.8328&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-hover: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report March 3, 2010 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration, American Eurocopter, ERA Helicopters - NTSB case key (mKey): 74681 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN09LA571 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74681/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74681 - Page: https://openairdocs.org/ntsb/CEN09LA571 ## Probable cause The pilot's inability to maintain control due to the mechanic's inadvertent switching of two cyclic control tubes of different lengths during maintenance. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Flight control system](https://openairdocs.org/ntsb-findings/01022700): Aircraft › Aircraft systems · Incorrect service/maintenance (probable cause); cases with it: [Messerschmitt-Boelkow-Blohm BO-105S, 2 cases](https://openairdocs.org/ntsb-findings/01022700/cases.md?model=5626006), [All aircraft, 65 cases](https://openairdocs.org/ntsb-findings/01022700/cases.md) - [Performance/control parameters](https://openairdocs.org/ntsb-findings/01062000): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Messerschmitt-Boelkow-Blohm BO-105S, 1 case](https://openairdocs.org/ntsb-findings/01062000/cases.md?model=5626006), [All aircraft, 1,269 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Messerschmitt-Boelkow-Blohm BO-105S, 1 case](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=5626006), [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. - [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040); cases with it: [Messerschmitt-Boelkow-Blohm BO-105S, 1 case](https://openairdocs.org/ntsb-events/040/sequence.md?model=5626006), [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md) - [Maneuvering-hover: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Messerschmitt-Boelkow-Blohm BO-105S, 1 case](https://openairdocs.org/ntsb-events/333/sequence.md?model=5626006), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) - [Maneuvering-hover: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Messerschmitt-Boelkow-Blohm BO-105S, 2 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=5626006), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Uncontrolled descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Messerschmitt-Boelkow-Blohm BO-105S, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=5626006), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis While in a 3-foot hover the helicopter began an uncommanded roll to the right. The pilot unsuccessfully attempted to arrest the roll by applying full left cyclic. Moments later the right landing skid made contact with the ground, followed by the main rotor blades. The helicopter came to rest in a right-side-low, upright position and the pilot was able to exit unassisted. The purpose of the flight was to perform an operational flight check of maintenance performed to the cyclic control system. The investigation revealed that the mechanic who had performed the maintenance had inadvertently switched two cyclic control tubes, of different lengths, during reassembly. This resulted in an out-of-rig condition in the cyclic control system. No other preimpact anomalies were noted with the helicopter's flight control system. ## Factual narrative On September 6, 2009, about 1400 central daylight time, a Messerschmitt-Boelkow-Blohm BO-105S helicopter, N131EH, was substantially damaged during a post maintenance flight near Thibodaux, Louisiana. The pilot, the sole occupant, sustained minor injuries. The helicopter was registered to and operated by ERA Helicopters LLC., of Lake Charles, Louisiana. Visual meteorological conditions prevailed and a company flight plan was filed for the 14 Code of Federal Regulations Part 91 local flight. According to the pilot, while in a 3-foot hover, the helicopter began an uncommanded roll to the right. The pilot attempted to arrest the roll by applying full left cyclic; however, the helicopter's roll could not be arrested. Moments later the right landing skid made contact with the ground followed by the main rotor blades. The helicopter came to rest in a right side low upright position and the pilot was able to exit unassisted. According to a Federal Aviation Administration (FAA) inspector who responded to the accident site, the purpose of the flight was to perform an operational flight check of maintenance performed to the cyclic control system. Prior to the accident flight, a company mechanic had removed both the lower lateral and longitudinal cyclic control tubes to replace the rod ends on both of the tubes. Although the lateral and longitudinal control tubes have the same part number, they are adjusted to different lengths. The rod ends were replaced with new ones and reinstalled in the helicopter; however, the investigation revealed that the mechanic had inadvertently switched the two control tubes during reassembly. This resulted in an out of rig condition in the cyclic control system. In addition, a bench check and a teardown were performed on the hydraulic control pack. There were no anomalies noted with the hydraulic system. Continuity was established in the "non-boosted" cyclic control system, and no anomalies were noted. The cyclic system above the hydraulic pack was damaged as result of the accident, but was functional. There also were no anomalies noted with the swashplate system or the main rotor system. ## Aircraft - Registration: [N131EH](https://openairdocs.org/deregistered/N131EH-2012-03-22), registration cancelled 2012-03-22, S/N S-595, built 1982 (OpenAirDocs) - Reported make and model: MESSERSCHMITT-BOELKOW-BLOHM BO-105S - Registry model: [Messerschmitt-Boelkow-Blohm BO-105S](https://openairdocs.org/model/messerschmitt-boelkow-blohm-bo-105s) (registry code 5626006) (OpenAirDocs) - Registry engine: [Allison 250-C20 series](https://openairdocs.org/engine/allison-250-c20-series) (registry code 03020, turbo-prop) (OpenAirDocs) - Category: Helicopter - Serial number: S-595 - Airframe hours: 16155 - Engines: ALLISON 250-C20 SER 420 horsepower turbo shaft; ALLISON 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Other work use, Part 91 - Operator: Era Helicopters LLC - Registered owner: Era Helicopters LLC - Airworthiness certificate: Standard, Normal - Last inspection: Continuous airworthiness, May 15, 2009 - Departed: L83, Thibodaux, LA - Destination: L83, Thibodaux, LA - Flight plan: Company VFR - Airport: L83, Thibodaux Municipal ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 61; injuries: minor; airline transport; instrument ratings: helicopter; medical: class 1, with waivers/limitations; last flight review August 13, 2009; seat: right; flight hours: 10,033 total, 1,969 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 270° at 5 knots - Visibility: 10 statute miles - Temperature: 84 °F ## 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 20090906019909A](https://openairdocs.org/incident/20090906019909A), Sep 6, 2009: Bolkms BO105S, Thibodaux, LA, Destroyed. The pilot reported that the helicopter entered and un-commanded right bank and right drift during hover. The pilot was unable to arrest the bank with full left… ## Docket (3 files) The files NTSB released with the investigation on November 3, 2009, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74681. 1.4 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 280 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40320084&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Statement of Party Representatives to NTSB Investigation (item 2, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40320086&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Digital Photo 1, Rear View (item 3, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40320087&FileExtension=.PDF&FileName=Digital%20Photo%201,%20Rear%20View-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.