# Main rotor drive, general

- Type: NTSB finding subsection
- Path: [Aircraft](https://openairdocs.org/ntsb-findings/01) › [Aircraft propeller/rotor](https://openairdocs.org/ntsb-findings/0104) › [Main rotor drive](https://openairdocs.org/ntsb-findings/010463) › Main rotor drive, general
- NTSB code: 01046300
- Cases: 15
- In the probable cause: 13
- Fatal cases: 2
- All cases: https://openairdocs.org/ntsb-findings/01046300/cases.md
- Cases with it in the probable cause: https://openairdocs.org/ntsb-findings/01046300/cases.md?cause=1
- Page: https://openairdocs.org/ntsb-findings/01046300

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

- 2008: 3 / 4
- 2009: 1 / 1
- 2010: 1 / 1
- 2011: 2 / 2
- 2012: 1 / 1
- 2014: 1 / 1
- 2016: 1 / 1
- 2017: 1 / 1
- 2020: 1 / 1
- 2021: 0 / 1
- 2023: 1 / 1

## Defining events in these cases

- [Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330): 7 cases
- [Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342): 3 cases
- [Loss of control in flight](https://openairdocs.org/ntsb-events/240): 2 cases
- [Loss of engine power (total)](https://openairdocs.org/ntsb-events/341): 1 cases
- [Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340): 1 cases
- [Roll over](https://openairdocs.org/ntsb-events/097): 1 cases

## Aircraft models (registry)

- [Robinson Helicopter R22 BETA](https://openairdocs.org/model/robinson-helicopter-r22-beta): 2 cases
- [Robinson Helicopter R44 II](https://openairdocs.org/model/robinson-helicopter-r44-ii): 1 cases
- [Robinson Helicopter R44](https://openairdocs.org/model/robinson-helicopter-r44): 1 cases
- [Hughes 269C](https://openairdocs.org/model/hughes-269c): 1 cases
- [Hiller UH-12E](https://openairdocs.org/model/hiller-uh-12e): 1 cases
- [D & D ROTORWAY EXEC](https://openairdocs.org/model/d-d-rotorway-exec): 1 cases
- [Bell OH-58C](https://openairdocs.org/model/bell-oh-58c): 1 cases
- [Bell 206B](https://openairdocs.org/model/bell-206b): 1 cases
- [Raymond Z Brown CONDOR](https://openairdocs.org/model/raymond-z-brown-condor): 1 cases
- [Dowell Vaughn EXEC-90](https://openairdocs.org/model/dowell-vaughn-exec-90): 1 cases

## Other findings in the same cases

- [Not determined, general](https://openairdocs.org/ntsb-findings/05000000) (Not determined): 2 cases
- [Aircraft control](https://openairdocs.org/ntsb-findings/02063040) (Personnel issues): 2 cases
- [Low light](https://openairdocs.org/ntsb-findings/03036015) (Environmental issues): 1 cases
- [Tree(s)](https://openairdocs.org/ntsb-findings/03022020) (Environmental issues): 1 cases
- [Wet/muddy terrain](https://openairdocs.org/ntsb-findings/03021035) (Environmental issues): 1 cases
- [Terrain, general](https://openairdocs.org/ntsb-findings/03021000) (Environmental issues): 1 cases
- [Use of policy/procedure](https://openairdocs.org/ntsb-findings/02063032) (Personnel issues): 1 cases
- [Installation](https://openairdocs.org/ntsb-findings/02062035) (Personnel issues): 1 cases
- [Scheduled/routine inspection](https://openairdocs.org/ntsb-findings/02061520) (Personnel issues): 1 cases
- [Decision making/judgment](https://openairdocs.org/ntsb-findings/02041520) (Personnel issues): 1 cases

## Newest cases

- [NTSB WPR24LA067](https://openairdocs.org/ntsb/WPR24LA067), Dec 24, 2023: Bell 206B (N111PM), El Centro, CA, substantial damage. Probable cause: An in-flight failure of the engine-to-transmission driveshaft due to a fatigue fracture of the forward-most flex plate in the forward KAflex coupling that resulted from a loose bolt attachment…
- [NTSB WPR21LA320](https://openairdocs.org/ntsb/WPR21LA320), Aug 14, 2021: Robinson Helicopter R22 Beta (N226WM), West Jordan, UT, substantial damage. Probable cause: The pilot receiving instruction’s improper application of forward cyclic in a low rotor rpm condition and the instructor’s delayed remediation, which resulted in an impact with terrain.
- [NTSB CEN20LA330](https://openairdocs.org/ntsb/CEN20LA330), Aug 8, 2020: Robinson R44 (N89LA), Logan, IA, substantial damage. Probable cause: The failure of the lower actuator bearing support brackets, which resulted in the misalignment of the clutch actuator, a loss of belt tension on the main rotor drive system, and a subsequent forced…
- [NTSB CEN17LA365](https://openairdocs.org/ntsb/CEN17LA365), Sep 16, 2017: Gaddis Michael Exec 162 F (N123XZ), Plymouth, IN, substantial damage. Probable cause: A failure of the drive belt for reasons that could not be determined based on the available information.
- [NTSB CEN16LA096](https://openairdocs.org/ntsb/CEN16LA096), Feb 1, 2016: Raymond Z Brown Condor (N41852), Centralia, IL, substantial damage, 1 fatal. Probable cause: The failure of the prerotator belt, which impeded the engine's timing belt and resulted in a loss of engine power at low altitude.
- [NTSB CEN14LA307](https://openairdocs.org/ntsb/CEN14LA307), Jun 21, 2014: Rotorway Exec 162F (N6828D), Mt. Comfort, IN, substantial damage. Probable cause: The pilot’s installation of an unauthorized main rotor belt and his subsequent failure to properly inspect the belt, which resulted in inadequate belt tension, the belt’s failure, and the subsequent…
- [NTSB WPR12FA191](https://openairdocs.org/ntsb/WPR12FA191), May 2, 2012: Hughes 269C (N380TL), Phoenix, AZ, substantial damage. Probable cause: A loss of tail rotor drive due to a fatigue failure of the main transmission pinion, which resulted in a loss of directional control during cruise flight.
- [NTSB CEN11LA305](https://openairdocs.org/ntsb/CEN11LA305), Apr 23, 2011: D & D Rotorway Exec (N614S), Massillon, OH, substantial damage. Probable cause: The excessive wear on the secondary shaft, from the inner bearing race, which resulted in the transmission clutch disengagement and a loss of power to the rotor system.
- [NTSB ERA11LA216](https://openairdocs.org/ntsb/ERA11LA216), Mar 25, 2011: Hiller UH-12E (N4033P), Culpeper, VA, substantial damage. Probable cause: Mechanical failure of the transmission for reasons that could not be determined because the transmission could not be torn down.
- [NTSB ERA10LA361](https://openairdocs.org/ntsb/ERA10LA361), Jul 15, 2010: Robinson Helicopter R22 Beta (N74603), West Melbourne, FL, substantial damage. Probable cause: Separation of the main rotor drive belts due to maintenance personnel’s failure to adequately inspect the upper drive sheave prior to installing the belts.

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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