# Main rotor head system

- Type: NTSB finding subsection
- Path: [Aircraft](https://openairdocs.org/ntsb-findings/01) › [Aircraft propeller/rotor](https://openairdocs.org/ntsb-findings/0104) › [Main rotor system](https://openairdocs.org/ntsb-findings/010462) › Main rotor head system
- NTSB code: 01046220
- Cases: 10
- In the probable cause: 10
- Fatal cases: 5
- All cases: https://openairdocs.org/ntsb-findings/01046220/cases.md
- Cases with it in the probable cause: https://openairdocs.org/ntsb-findings/01046220/cases.md?cause=1
- Page: https://openairdocs.org/ntsb-findings/01046220

## Cases per year (in the probable cause / all)

- 2008: 2 / 2
- 2009: 1 / 1
- 2011: 2 / 2
- 2012: 1 / 1
- 2013: 1 / 1
- 2015: 1 / 1
- 2016: 1 / 1
- 2022: 1 / 1

## Defining events in these cases

- [Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330): 2 cases
- [Collision during takeoff/land](https://openairdocs.org/ntsb-events/490): 1 cases
- [External load event (Rotorcraft)](https://openairdocs.org/ntsb-events/480): 1 cases
- [Part(s) separation from AC](https://openairdocs.org/ntsb-events/338): 1 cases
- [Aircraft structural failure](https://openairdocs.org/ntsb-events/337): 1 cases
- [Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333): 1 cases
- [Mast bumping](https://openairdocs.org/ntsb-events/245): 1 cases
- [Loss of control in flight](https://openairdocs.org/ntsb-events/240): 1 cases
- [Unknown or undetermined](https://openairdocs.org/ntsb-events/000): 1 cases

## Aircraft models (registry)

- [Hiller UH-12E](https://openairdocs.org/model/hiller-uh-12e): 2 cases
- [S N I A S AS-350B ECUREUIL](https://openairdocs.org/model/s-n-i-a-s-as-350b-ecureuil): 1 cases
- [Robinson Helicopter R66](https://openairdocs.org/model/robinson-helicopter-r66): 1 cases
- [Robinson Helicopter R22 BETA](https://openairdocs.org/model/robinson-helicopter-r22-beta): 1 cases
- [Hiller UH-12D](https://openairdocs.org/model/hiller-uh-12d): 1 cases
- [Bell 214ST](https://openairdocs.org/model/bell-214st): 1 cases
- [American Eurocopter AS350B3](https://openairdocs.org/model/american-eurocopter-as350b3): 1 cases
- [Pearson Jon M DRAGONFLY](https://openairdocs.org/model/pearson-jon-m-dragonfly): 1 cases
- [Gauchat Michael SAFARI](https://openairdocs.org/model/gauchat-michael-safari): 1 cases

## Other findings in the same cases

- [Manufacture/production, general](https://openairdocs.org/ntsb-findings/04013000) (Organizational issues): 1 cases
- [Ground equipment](https://openairdocs.org/ntsb-findings/03022050) (Environmental issues): 1 cases
- [Use of equip/system](https://openairdocs.org/ntsb-findings/02063015) (Personnel issues): 1 cases
- [Installation](https://openairdocs.org/ntsb-findings/02062035) (Personnel issues): 1 cases
- [Delayed action](https://openairdocs.org/ntsb-findings/02041025) (Personnel issues): 1 cases
- [Pitch control](https://openairdocs.org/ntsb-findings/01062022) (Aircraft): 1 cases
- [Performance/control parameters, general](https://openairdocs.org/ntsb-findings/01062000) (Aircraft): 1 cases
- [Main rotor control](https://openairdocs.org/ntsb-findings/01046710) (Aircraft): 1 cases
- [Main rotor mast/swashplate](https://openairdocs.org/ntsb-findings/01046230) (Aircraft): 1 cases
- [Main rotor blade system](https://openairdocs.org/ntsb-findings/01046210) (Aircraft): 1 cases

## Newest cases

- [NTSB CEN22LA318](https://openairdocs.org/ntsb/CEN22LA318), Jul 6, 2022: Hiller UH12E (N64272), Becker, MN, substantial damage. Probable cause: The in-flight failure of the main rotor mast hub due to several undetected fatigue fractures.
- [NTSB CEN16LA330](https://openairdocs.org/ntsb/CEN16LA330), Aug 23, 2016: Hiller UH 12D (N97TH), Cokeville, WY, substantial damage. Probable cause: Failure of the control rotor cuff due to fatigue.
- [NTSB GAA15CA258](https://openairdocs.org/ntsb/GAA15CA258), Sep 9, 2015: Airbus AS350 (N253HP), Draper, UT, substantial damage. Probable cause: The ground recovery team member's failure to secure a rescue rope during the helicopter loading process in steep terrain, resulting in the rope fouling the helicopter's main rotor system.
- [NTSB CEN14LA056](https://openairdocs.org/ntsb/CEN14LA056), Nov 16, 2013: Pearson Jon M Dragonfly (N975DF), Anahuac, TX, destroyed, 1 fatal. Probable cause: The incorrect installation by the pilot, who was not a certificated mechanic or repairman, of the main rotor head bearing block, which resulted in the in-flight separation of the rotor head.
- [NTSB DCA12FA024](https://openairdocs.org/ntsb/DCA12FA024), Jan 16, 2012: Bell 214 (N5748M), Camp Bastion, Afghanistan, destroyed, 3 fatal. Probable cause: the overtravel of the collective sleeve, which led to a severe and sudden reduction in main rotor blade collective pitch, resulting in a loss of control of the helicopter. The reason for the…
- [NTSB CEN12FA001](https://openairdocs.org/ntsb/CEN12FA001), Oct 1, 2011: Robinson Helicopter R66 (N266CY), Philip, SD, destroyed, 1 fatal. Probable cause: The in-flight separation of the main rotor mast following a mast bumping event. The reason for the mast bumping event could not be determined due to postaccident damage.
- [NTSB CEN11FA422](https://openairdocs.org/ntsb/CEN11FA422), Jun 27, 2011: Robinson R22 Beta (N7779M), Del Valle, TX, substantial damage, 1 fatal. Probable cause: The divergence of the main rotor from its normal plane of rotation for reasons that cannot be determined because the pilot’s control inputs leading up to the event are unknown, resulting in mast…
- [NTSB WPR09LA253](https://openairdocs.org/ntsb/WPR09LA253), May 22, 2009: Gauchat Safari (N147MD), Rock Springs, AZ, substantial damage, 2 fatal. Probable cause: The separation of the main rotor head during cruise flight as a result of cyclic fatigue of the main rotor head spindle. The fatigue crack was due to an inadequate manufacturing process.
- [NTSB MIA08LA199](https://openairdocs.org/ntsb/MIA08LA199), Sep 19, 2008: Eurocopter AS-350-BA (N906BA), Linden, NJ, substantial damage. Probable cause: The flight instructor’s delayed remedial action (flight control inputs) during a practice autorotation/run-on landing resulting in fracture damage to the main rotor system Starflex.
- [NTSB NYC08LA318](https://openairdocs.org/ntsb/NYC08LA318), Sep 16, 2008: Hiller UH-12E (N3324F), Naruna, VA, substantial damage. Probable cause: The fatigue failure of a main rotor blade drag strut.

NTSB has coded findings and defining events since 2008; earlier cases used its older occurrence and cause codes and aren't counted.

Findings: https://openairdocs.org/ntsb-findings.md. Defining events: https://openairdocs.org/ntsb-events.md. Phases of flight: https://openairdocs.org/ntsb-phases.md. Every investigation, filtered by finding, event, phase, state, year or model: https://openairdocs.org/ntsb.md (for example ?state=MI&fatal=1).

NTSB's definitions: Accident and incident, 49 CFR 830.2 (https://www.ecfr.gov/current/title-49/subtitle-B/chapter-VIII/part-830/subpart-A/section-830.2), CICTT occurrence categories (PDF) (https://www.ntsb.gov/safety/data/Documents/datafiles/OccurrenceCategoryDefinitions.pdf), CICTT phases of flight (PDF) (https://www.ntsb.gov/safety/data/Documents/datafiles/PhaseofFlightDefinitions.pdf), and NTSB coding manual, before 2008 (PDF) (https://www.ntsb.gov/GILS/Documents/codman.pdf). NTSB publishes no definitions for its findings, only their names.

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