# NTSB LAX04TA052: Eurocopter France AS 350 B3, N846BP, Yuma, AZ, November 25, 2003 - Type: NTSB accident investigation - Classification: Accident · No injuries · Final report - Date: November 24, 2003, 19:00 local (Nov 25, 2003, 02:00 UTC) - Place: Yuma, AZ - Coordinates: 32.654998, -114.606666 - Nearby events: https://openairdocs.org/map.md?lat=32.6550&lon=-114.6067&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report December 28, 2004 - Report: Approved by Office Director - Parties: Federal Aviation Administration - NTSB case key (mKey): 58399 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX04TA052 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/58399/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=58399 - Page: https://openairdocs.org/ntsb/LAX04TA052 ## Probable cause The malfunction of the rotor drive system due to improper maintenance, which resulted in the uncoupling of the drive shaft during takeoff-initial climb. A factor associated with the accident is the undertorqued drive system bolts. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, takeoff - initial climb - miscellaneous,bolt/nut/fastener/clamp/spring - undertorqued (contributing factor) - miscellaneous,bolt/nut/fastener/clamp/spring - not safetied (cause) - miscellaneous,bolt/nut/fastener/clamp/spring - failure,total (cause) - maintenance - improper, company maintenance personnel (cause) - Forced landing, emergency landing after takeoff - Hard landing, emergency landing ## Analysis The helicopter encountered a total loss of drive to the rotor system a few seconds after takeoff, about 20 feet above the ground. The helicopter touched down hard and was substantially damaged. Company mechanics had performed maintenance on the helicopter that involved handling of the rotor drive shaft and a flex coupling. The flex coupling is normally secured with three bolts and self locking nuts. The manufacturer's maintenance procedure requires that during installation, the nuts are torqued and then cotter pins are inserted. During the wreckage examination, the bolts were found sheared, and no evidence of cotter pins were found. According to the manufacturer, even if the cotter pins are not installed, if the bolts are adequately torqued, they should not become loose. ## Factual narrative On November 24, 2003, about 1900 mountain standard time, a Eurocopter AS 350 B3, N846BP, made a hard forced landing at the Yuma MCAS International Airport, Yuma, Arizona. The commercial pilot and a crewmember (observer) sustained no injuries. The helicopter was owned and operated by the United States Border Patrol (USPB), Air Operations, El Paso, Texas, and it was substantially damaged during the public-use flight. Visual meteorological conditions prevailed during the nighttime patrol flight that was performed under the provisions of 14 CFR Part 91. A company flight plan was filed. The flight was originating at the time of the accident. The operator indicated that a few seconds after taking off, a mechanical malfunction occurred about 20 feet above ground level. The pilot made a forced landing during which the helicopter touched down hard. During the subsequent examination of the helicopter, the flex coupling between the engine drive shaft and the main gear box drive was found separated. The three bolts in the flex coupling assembly were found sheared. A further examination of the bolts revealed that they were devoid of three required cotter pins. The American Eurocopter Corporation's U.S. manager of accident investigation reported to the National Transportation Safety Board investigator that company records indicated that the accident helicopter was delivered to the USPB with the cotter pins installed. A subsequent examination of the broken components in the wreckage revealed evidence that at some point in time cotter pins had been installed in the bolts. However, no cotter pins were found in the wreckage. American Eurocopter’s accident investigation manager opined that the component examination performed by Eurocopter France's materials laboratory indicated that both sides of the flats on the recovered nuts revealed evidence of marks consistent with mechanical damage (see attached report). Maintenance records indicated that, following the helicopter's sale to the USBP, USBP mechanics performed a module 1 change. In addition, other maintenance was performed such as installation of an air conditioner. This maintenance may have involved manipulation of the drive. Maintenance or handling of the drive, if performed in accordance with Eurocopter's maintenance manual, would have required removing the three cotter pins and unscrewing (untorquing) the self locking flex coupling bolts. Regarding the effect of having the flex coupling disconnect, according to American Eurocopter's manager of accident investigation, when the bolts sheared, their disconnection from the drive shaft to the coupling flange link resulted in a total loss of drive to the rotors. The manager further reported that when properly installed, the subject self locking nuts are torqued, and then they are cotter pinned. Even if the cotter pins are not installed, when properly torqued the nuts should not unscrew. ## Aircraft - Registration: [N846BP](https://openairdocs.org/aircraft/N846BP), registered now, S/N 3542, built 2002 (OpenAirDocs) - Reported make and model: Eurocopter France AS 350 B3 - Registry model: [Eurocopter AS 350 B3](https://openairdocs.org/model/eurocopter-as-350-b3) (registry code 8680954) (OpenAirDocs) - Registry engine: [Turbomeca ARRIUS-2B series](https://openairdocs.org/engine/turbomeca-arrius-2b-series) (registry code 60013, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 3542 - Airframe hours: 813 - Engines: Turbomeca Arriel A2 847 horsepower turbo shaft - Damage: Substantial damage - Flight: Public aircraft, Public use - Registered owner: U.S. Border Patrol, Air Operations - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, November 20, 2003, 13 hours before - Departed: YUM, Yuma, AZ - Destination: YUM - Flight plan: Company VFR - Airport: YUM, Yuma MCAS International ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 45; injuries: minor; commercial; airplane ratings: single-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--w/ waivers/lim; last flight review July 10, 2003; seat: right; flight hours: 6,273 total, 202 in this make and model, 4,921 as pilot in command, 250 in the last 90 days, 60 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Night/bright - Wind: 40° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: 12,000 ft broken - Temperature: 61 °F, dew point 19 °F - Altimeter: 29.88 inHg - Observed at: YUM ## 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 20031124031279A](https://openairdocs.org/incident/20031124031279A), Nov 24, 2003: Snias AS350B3, Yuma, AZ, Substantial damage. (-23) Public use aircraft, belonging to us border patrol. AS-350B3, N846BP piloted by joseph william dunn a commercial pilot certificate #526254488. Aircraft… ## Docket (3 files) The files NTSB released with the investigation on November 4, 2004, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=58399. 3.4 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 397 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40220024&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Drawings: Maintenance Figure Extract (item 2, .PDF, 61 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40220031&FileExtension=.PDF&FileName=Drawings%3A%20Maintenance%20Figure%20Extract-Master.PDF - Eurocopter Materials Laboratory Report (item 3, .PDF, 2.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40221201&FileExtension=.PDF&FileName=Eurocopter%20Materials%20Laboratory%20Report-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.