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Location:
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Becker, Minnesota
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Accident Number:
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CEN22LA318
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Date & Time:
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July 6, 2022, 10:15 Local
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Registration:
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N64272
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Aircraft:
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Hiller UH12E
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Aircraft Damage:
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Substantial
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Defining Event:
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Sys/Comp malf/fail (non-power)
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Injuries:
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1 Serious
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Flight Conducted Under:
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Part 137: Agricultural
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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.
Probable Cause and Findings
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The in-flight failure of the main rotor mast hub due to several undetected fatigue fractures.
Findings
Aircraft Main rotor head system - Fatigue/wear/corrosion
Aircraft (general) - Failure
Factual Information
History of Flight
Maneuvering Sys/Comp malf/fail (non-power) (Defining event)
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.
Pilot Information
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Certificate:
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Private
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Age:
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54,Male
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Airplane Rating(s):
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None
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Seat Occupied:
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Single
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Other Aircraft Rating(s):
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Helicopter
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Restraint Used:
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Instrument Rating(s):
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None
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Second Pilot Present:
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No
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Instructor Rating(s):
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None
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Toxicology Performed:
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Medical Certification:
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Unknown
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Last FAA Medical Exam:
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Occupational Pilot:
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UNK
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Last Flight Review or Equivalent:
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April 1, 2022
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Flight Time:
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(Estimated) 5957.8 hours (Total, all aircraft)
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Aircraft and Owner/Operator Information
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Aircraft Make:
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Hiller
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Registration:
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N64272
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Model/Series:
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UH12E
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Aircraft Category:
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Helicopter
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Year of Manufacture:
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1965
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Amateur Built:
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Airworthiness Certificate:
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Restricted (Special)
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Serial Number:
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1679
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Landing Gear Type:
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High skid
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Seats:
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4
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Date/Type of Last
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July 2, 2022 100 hour
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Certified Max Gross Wt.:
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2750 lbs
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Inspection:
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|
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Time Since Last Inspection:
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9.6 Hrs
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Engines:
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1 Reciprocating
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Airframe Total Time:
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10285.9 Hrs at time of
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Engine Manufacturer:
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Lycoming
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accident
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ELT:
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Not installed
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Engine Model/Series:
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VO-540-C2A
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Registered Owner:
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DECHENE CORP
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Rated Power:
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340 Horsepower
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Operator:
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Triple H Aviation
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Operating Certificate(s)
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Agricultural aircraft (137)
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Held:
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Operator Does Business As:
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Triple H Aviation
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Operator Designator Code:
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Meteorological Information and Flight Plan
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Conditions at Accident Site:
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Visual (VMC)
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Condition of Light:
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Day
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Observation Facility, Elevation:
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KMGG,1028 ft msl
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Distance from Accident Site:
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11 Nautical Miles
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Observation Time:
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10:07 Local
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Direction from Accident Site:
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207°
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Lowest Cloud Condition:
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Visibility
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10 miles
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Lowest Ceiling:
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Overcast / 600 ft AGL
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Visibility (RVR):
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Wind Speed/Gusts:
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5 knots /
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Turbulence Type
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/
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Forecast/Actual:
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Wind Direction:
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50°
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Turbulence Severity
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/
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Forecast/Actual:
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Altimeter Setting:
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30.06 inches Hg
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Temperature/Dew Point:
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19°C / 15°C
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Precipitation and Obscuration:
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No Obscuration; No Precipitation
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Departure Point:
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Becker, MN
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Type of Flight Plan Filed:
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None
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Destination:
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Becker, MN
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Type of Clearance:
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None
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Departure Time:
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Type of Airspace:
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Class G
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Wreckage and Impact Information
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Crew Injuries:
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1 Serious
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Aircraft Damage:
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Substantial
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Passenger
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Aircraft Fire:
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None
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Injuries:
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|
|
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Ground Injuries:
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Aircraft Explosion:
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None
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Total Injuries:
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1 Serious
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Latitude,
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45.394738,-93.872706(est)
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Longitude:
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|
Administrative Information
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Investigator In Charge (IIC):
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Aguilera, Jason
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Additional Participating
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Greg Thurston; FAA FSDO; Minneapolis, MN
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Persons:
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Original Publish Date:
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July 5, 2024
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Last Revision Date:
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Investigation Class:
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Class 3
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Note:
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The NTSB did not travel to the scene of this accident.
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Investigation Docket:
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https://data.ntsb.gov/Docket?ProjectID=105500
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The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant events in other modes of transportation— railroad, transit, highway, marine, pipeline, and commercial space. We determine the probable causes of the accidents and events we investigate, and issue safety recommendations aimed at preventing future occurrences. In addition, we conduct transportation safety research studies and offer information and other assistance to family members and survivors for each accident or event we investigate. We also serve as the appellate authority for enforcement actions involving aviation and mariner certificates issued by the Federal Aviation Administration (FAA) and US Coast Guard, and we adjudicate appeals of civil penalty actions taken by the FAA.
The NTSB does not assign fault or blame for an accident or incident; rather, as specified by NTSB regulation, “accident/incident investigations are fact-finding proceedings with no formal issues and no adverse parties … and are not conducted for the purpose of determining the rights or liabilities of any person” (Title 49 Code of Federal Regulations section 831.4). Assignment of fault or legal liability is not relevant to the NTSB’s statutory mission to improve transportation safety by investigating accidents and incidents and issuing safety recommendations. In addition, statutory language prohibits the admission into evidence or use of any part of an NTSB report related to an accident in a civil action for damages resulting from a matter mentioned in the report (Title 49 United States Code section 1154(b)). A factual report that may be admissible under 49 United States Code section 1154(b) is available here.
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