# NTSB CEN22LA318: Hiller UH12E, N64272, Becker, MN, July 6, 2022 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 3 · Limited · Final report - Date: July 6, 2022, 10:15 local (15:15 UTC) - Place: Becker, MN · Crashed in a field. Waiting on Lat-Long - Coordinates: 45.394738, -93.872706 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.3947&lon=-93.8727&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA FSDO - ADs cited in the narratives: [AD 73-20-03](https://openairdocs.org/ad/73-20-03) (OpenAirDocs) - NTSB case key (mKey): 105500 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN22LA318 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/105500/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=105500 - Page: https://openairdocs.org/ntsb/CEN22LA318 ## Probable cause The in-flight failure of the main rotor mast hub due to several undetected fatigue fractures. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Main rotor system](https://openairdocs.org/ntsb-findings/01046200): Aircraft › Aircraft propeller/rotor · Failure (probable cause); cases with it: [Hiller UH-12E, 1 case](https://openairdocs.org/ntsb-findings/01046200/cases.md?model=4360122), [All aircraft, 25 cases](https://openairdocs.org/ntsb-findings/01046200/cases.md) - [Main rotor system: main rotor head system](https://openairdocs.org/ntsb-findings/01046220): Aircraft › Aircraft propeller/rotor · Fatigue/wear/corrosion (probable cause); cases with it: [Hiller UH-12E, 2 cases](https://openairdocs.org/ntsb-findings/01046220/cases.md?model=4360122), [All aircraft, 10 cases](https://openairdocs.org/ntsb-findings/01046220/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Hiller UH-12E, 5 cases](https://openairdocs.org/ntsb-events/330/sequence.md?model=4360122), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) ## Analysis While the pilot was conducting an aerial application flight, he felt a small jolt, the main rotor mast failed, and the helicopter collided with terrain. Four days before the accident, a mechanic performed a dye penetrant inspection on the rotor mast; the helicopter had only flown 9 hours since the inspection. Attempts to retrieve the rotor mast parts from the operator were unsuccessful and when contact was reestablished with the owner, he had already disposed of the parts. Photos of the broken rotor hub were reviewed by the National Transportation Safety Board (NTSB) Materials Laboratory, which determined that several preexisting, progressive cracks were present. ## Factual narrative On July 6, 2022, about 1015 central daylight time, a Hiller UH-12E helicopter, N64272, was substantially damaged when it was involved in an accident near Becker, Minnesota. The pilot was seriously injured. The helicopter was operated under the provisions of Title 14 Code of Federal Regulations Part 137 as an aerial application flight. According to information collected by a Federal Aviation Administration (FAA) inspector, the pilot was applying product to a potato field when he felt a small jolt and the helicopter collided with terrain. The operator transported the helicopter back to the their facility about a week before they notified the NTSB or FAA of the accident, so neither agency was able to perform on-scene documentation. The operator reported that the main rotor mast had failed; the yellow blade was found about 500 ft west of the main wreckage and the blue blade was found about 300 ft east of the main wreckage. The mast, with a part of the transmission, was found about 150 ft northeast of the blue blade. An FAA review of maintenance records found that the main rotor hub (p/n 51437-23) was installed on the helicopter on December 14, 2018. Four days before the accident, a mechanic performed a 100-hour inspection, which included compliance with Airworthiness Directive (AD) 73-20-03. This AD requires dye penetrant inspection of the main rotor hub at 50-hour intervals to detect cracks. The helicopter had accumulated 9 flight hours since the inspection. Attempts to retrieve the parts from the operator were unsuccessful; when the NTSB reestablished contact with the owner, he had already disposed of the parts. The NTSB Materials Laboratory reviewed photos of the broken rotor hub. The photos showed evidence of several preexisting, progressive fatigue failures. ## Aircraft - Registration: [N64272](https://openairdocs.org/deregistered/N64272-2023-03-06), registration cancelled 2023-03-06, S/N 1679, built 1965 (OpenAirDocs) - Reported make and model: HILLER UH12E - Registry model: [Hiller UH-12E](https://openairdocs.org/model/hiller-uh-12e) (registry code 4360122) (OpenAirDocs) - Registry engine: [Lycoming IO-540 series](https://openairdocs.org/engine/lycoming-io-540-series) (registry code 41530, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 1679 - Year built: 1965 - Airframe hours: 10285.9 - Engines: Lycoming VO-540-C2A 340 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Triple H Aviation, doing business as Triple H Aviation - Registered owner: Dechene Corp - Airworthiness certificate: Special, Restricted (Special) - Last inspection: 100 hour, July 2, 2022, 9.6 hours before - Departed: Becker, MN - Destination: Becker, MN - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; injuries: none; private; medical: unknown; last flight review April 1, 2022; seat: single; flight hours: 5,957.8 total ## Weather - Conditions: Visual (VMC), Day - Wind: 50° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: 600 ft overcast - Temperature: 66 °F, dew point 59 °F - Altimeter: 30.06 inHg - Observed at: KMGG, 11 nm away - METAR: KMGG 061507Z AUTO 05005KT 10SM OVC006 19/15 A3006 RMK AO2 ## 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 20220706007819A](https://openairdocs.org/incident/20220706007819A), Jul 6, 2022: Hiller UH-12E, Becker, MN, Substantial damage. 2022-07-06 N64272 crashed in potato field while performing 137 agricultural application. PIC had been spraying a potato field in N64272 for approximately 5… ## Docket (7 files) The files NTSB released with the investigation on July 5, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=105500. 9.4 MB in all. - Record of conversation operator (item 1, PDF, 1 page, 67 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16961772&FileExtension=pdf&FileName=Record%20of%20Conversation%20Operator-Rel.pdf - Record of conversation FAA (item 2, PDF, 1 page, 67 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17163890&FileExtension=pdf&FileName=Record%20of%20Conversation%20FAA-Rel.pdf - Photos (item 3, PDF, 5 pages, 4 photos, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17260812&FileExtension=pdf&FileName=Photos%204-Rel.pdf - Maintenance records (item 4, PDF, 3 pages, 4.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17261251&FileExtension=pdf&FileName=Maintenance%20Records_Redacted-Rel.pdf - Maintenace records summary (item 5, PDF, 1 page, 62 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17270216&FileExtension=pdf&FileName=mx%20record%20summary-Rel.pdf - Hiller airworthiness directive 73-20-03 (item 6, PDF, 2 pages, 102 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16961443&FileExtension=pdf&FileName=AD%2073-20-03-Rel.pdf - NTSB materials lab (item 7, PDF, 6 pages, 7 photos, 3.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17262418&FileExtension=pdf&FileName=NTSB%20Materials%20Lab-Rel.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.