# NTSB CEN09LA565: Bell UH-1B, N204JB, Arvilla, ND, September 6, 2009 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: September 6, 2009, 08:05 local (13:05 UTC) - Place: Arvilla, ND - Coordinates: 47.917778, -97.494445 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.9178&lon=-97.4944&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed, report April 22, 2010 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA-FAR-FSDO, Bell Helicopter - NTSB case key (mKey): 74668 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN09LA565 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74668/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74668 - Page: https://openairdocs.org/ntsb/CEN09LA565 ## Probable cause The aircraft owner/mechanic/pilot's installation of an improper tail boom assembly and the resulting fatigue failure of the tail boom's attach fittings. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Fuselage: rotorcraft tail boom](https://openairdocs.org/ntsb-findings/01035302): Aircraft › Aircraft structures · Fatigue/wear/corrosion (probable cause); cases with it: [Bell UH-1B, 2 cases](https://openairdocs.org/ntsb-findings/01035302/cases.md?model=1181410), [All aircraft, 12 cases](https://openairdocs.org/ntsb-findings/01035302/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Bell UH-1B, 1 case](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=1181410), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) - [Fuselage: rotorcraft tail boom](https://openairdocs.org/ntsb-findings/01035302): Aircraft › Aircraft structures · Incorrect service/maintenance (probable cause); cases with it: [Bell UH-1B, 2 cases](https://openairdocs.org/ntsb-findings/01035302/cases.md?model=1181410), [All aircraft, 12 cases](https://openairdocs.org/ntsb-findings/01035302/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) (defining event); cases with it: [Bell UH-1B, 1 case](https://openairdocs.org/ntsb-events/337/sequence.md?model=1181410), [All aircraft, 290 cases](https://openairdocs.org/ntsb-events/337/sequence.md) - [Maneuvering: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Bell UH-1B, 2 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=1181410), [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: [Bell UH-1B, 4 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1181410), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The helicopter pilot reported that he heard a “crack” and a “bang” when he pulled up at the end of the field during the spray run. He stated the helicopter began spinning to the right as it gained altitude. He rolled off the throttle and was able to clear a row of trees at the end of the field. The helicopter impacted the terrain on one side of the tree line and the tail boom was located approximately 100 feet away, on the other side of the tree line. The examination revealed the tail boom’s upper left attach fitting contained fatigue fractures that originated at the upper and lower rivet holes. Corrosion was also present along the fractured surface. The tail boom’s upper right attachment bolt contained a fatigue fracture which had multiple origins. The tail boom’s lower right attach fitting fractured as a result of overload. The tail boom involved in this accident was installed on the helicopter on February 20, 2006, and had been removed from a UH-1F helicopter. The UH-1F tail boom is 23.8 inches longer than the UH-1B tail boom that was originally on the helicopter. The pilot/owner, who is an airframe and powerplant mechanic with inspection authority, performed this maintenance. There is no load data nor is there a Supplemental Type Certificate available for this installation. ## Factual narrative On September 6, 2009, at 0805 central daylight time, a Bell UH-1B, N204JB, experienced a tail boom separation during an aerial application flight in Arvilla, North Dakota. The pilot received serious injuries. The helicopter received substantial damage to the fuselage and tail boom. The flight was being operated under Title 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed and no flight plan was filed. The local flight originated from the Morten Airport (62ND), Larimore, North Dakota, shortly before the accident. The pilot reported that he heard a “crack” and a “bang” when he pulled up at the end of the field during the spray run. He stated the helicopter began spinning to the right as it gained altitude. He rolled off the throttle and was able to clear a row of trees at the end of the field. The helicopter impacted the terrain on one side of the tree line, and the tail boom was located approximately 100 feet away on the other side of the tree line. A piece of the aft fuselage bulkhead was located approximately 100 feet from the tail boom. Examination of the tail boom revealed the upper left attach point fitting was separated from the tail boom. The bolt along with the forward portion of the fitting remained attached to the fuselage. The bolt from the lower left attach point fitting was missing. The bolt hole was slightly elongated and the bulkhead was slightly buckled. Half of the upper right attach point bolt was missing. The lower right attach fitting was in place and a portion of the fuselage bulkhead was separated from the fuselage bulkhead and remained with the fitting. Pieces of the tail boom’s upper left attach fitting, the upper right attach bolt, and a portion of the lower right attach fitting and bolt were removed from the helicopter. These components were examined at the Bell Helicopter laboratory under the supervision of the Safety Board. The examination revealed the tail boom’s upper left attach fitting contained fatigue fractures that originated at the upper and lower rivet holes. Corrosion was also present along the fractured surface. The tail boom’s upper right attachment bolt contained a fatigue fracture which had multiple origins. The tail boom’s lower right attach fitting fractured as a result of overload. According to the helicopter operator and maintenance records, the tail boom involved in this accident was installed on the helicopter on February 20, 2006. This tail boom, serial number BBBF-0002, part number 204-200-022-3A, had been removed from a Bell UH-1F. The UH-1F tail boom is 23.8 inches longer than the UH-1B tail boom that was originally on the helicopter. Longer main rotor blades were also installed on the helicopter at the same time. The pilot/owner, who is an airframe and powerplant mechanic with inspection authority, performed his own maintenance. According to Bell Helicopter, there is no load data available for UH-1B helicopters with a UH-1F tail boom installation, nor is therean Supplemental Type Certificate available for this installation. ## Aircraft - Registration: [N204JB](https://openairdocs.org/aircraft/N204JB), registered now, S/N 63-13088, built 1963 (OpenAirDocs) - Reported make and model: BELL UH-1B - Registry model: [Bell UH-1B](https://openairdocs.org/model/bell-uh-1b) (registry code 1181410) (OpenAirDocs) - Registry engine: [Lycoming T-53 series](https://openairdocs.org/engine/lycoming-t-53-series) (registry code 41549, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 63-13088 - Airframe hours: 9587 - Engines: LYCOMING T-53L13BA 1400 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Morten Jesse L - Registered owner: Morten Jesse L - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, February 6, 2009, 17 hours before - Departed: 62ND, Larimore, ND ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 49; injuries: serious; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: helicopter, airplane; medical: class 2, with waivers/limitations; last flight review March 10, 2008; seat: right; flight hours: 14,000 total, 1,000 in this make and model, 13,900 as pilot in command, 120 in the last 90 days, 0 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 180° at 7 knots - Visibility: 7 statute miles - Lowest ceiling: none - Temperature: 61 °F, dew point 59 °F - Altimeter: 30.05 inHg - Observed at: GFK, 6 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 20090906025899A](https://openairdocs.org/incident/20090906025899A), Sep 6, 2009: Bell UH-1B, Arvilla, ND, Destroyed. While on a 14 CFR part 137 commercial revenue flight, performing aerial applications, an appropriately rated and certificated pilot experienced a loud noise… ## Other investigations on N204JB (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 BFO94LA159](https://openairdocs.org/ntsb/BFO94LA159), Aug 31, 1994: Bell UH-1B (N204JB), Carrabasset, ME, substantial damage. Probable cause: Fracture failure of the tail rotor drive intermediate gearbox. ## Docket (10 files) The files NTSB released with the investigation on December 3, 2009, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74668. 15.0 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 754 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321914&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Bell Helicopter Laboratory Report (item 2, .PDF, 10.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321915&FileExtension=.PDF&FileName=Bell%20Helicopter%20Laboratory%20Report-Master.PDF - Maintenance Records (item 3, .PDF, 480 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321916&FileExtension=.PDF&FileName=Maintenance%20Records-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 4, .PDF, 382 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321917&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.PDF - Photo 1. Separated Tail Boom (item 5, .PDF, 679 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321920&FileExtension=.PDF&FileName=Photo%201.%20%20Separated%20Tail%20Boom-Master.PDF - Photo 2. Helicopter Fuselage (item 6, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321921&FileExtension=.PDF&FileName=Photo%202.%20%20Helicopter%20Fuselage-Master.PDF - Photo 3. Lower Left Tail Boom Fitting (item 7, .PDF, 337 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321922&FileExtension=.PDF&FileName=Photo%203.%20%20Lower%20Left%20Tail%20Boom%20Fitting-Master.PDF - Photo 4. Lower Right Tail Boom Fitting (item 8, .PDF, 252 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321923&FileExtension=.PDF&FileName=Photo%204.%20%20Lower%20Right%20Tail%20Boom%20Fitting-Master.PDF - Photo 5. Upper Right Tail Boom Fitting (item 9, .PDF, 317 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321924&FileExtension=.PDF&FileName=Photo%205.%20%20Upper%20Right%20Tail%20Boom%20Fitting-Master.PDF - Photo 6. Upper Left Tail Boom Fitting (item 10, .PDF, 174 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40321925&FileExtension=.PDF&FileName=Photo%206.%20%20Upper%20Left%20Tail%20Boom%20Fitting-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.