# Tail rotor drive system, general

- Type: NTSB finding subsection
- Path: [Aircraft](https://openairdocs.org/ntsb-findings/01) › [Aircraft propeller/rotor](https://openairdocs.org/ntsb-findings/0104) › [Tail rotor drive system](https://openairdocs.org/ntsb-findings/010465) › Tail rotor drive system, general
- NTSB code: 01046500
- Cases: 10
- In the probable cause: 10
- Fatal cases: 0
- All cases: https://openairdocs.org/ntsb-findings/01046500/cases.md
- Cases with it in the probable cause: https://openairdocs.org/ntsb-findings/01046500/cases.md?cause=1
- Page: https://openairdocs.org/ntsb-findings/01046500

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

- 2008: 1 / 1
- 2011: 1 / 1
- 2012: 2 / 2
- 2014: 1 / 1
- 2015: 1 / 1
- 2018: 1 / 1
- 2019: 2 / 2
- 2024: 1 / 1

## Defining events in these cases

- [Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333): 4 cases
- [Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330): 2 cases
- [Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340): 1 cases
- [Part(s) separation from AC](https://openairdocs.org/ntsb-events/338): 1 cases
- [Loss of tail rotor effectiveness](https://openairdocs.org/ntsb-events/242): 1 cases
- [Loss of control in flight](https://openairdocs.org/ntsb-events/240): 1 cases

## Aircraft models (registry)

- [Robinson Helicopter R44](https://openairdocs.org/model/robinson-helicopter-r44): 2 cases
- [Schweizer 269C](https://openairdocs.org/model/schweizer-269c): 1 cases
- [Robinson Helicopter R44 II](https://openairdocs.org/model/robinson-helicopter-r44-ii): 1 cases
- [Hughes 269C](https://openairdocs.org/model/hughes-269c): 1 cases
- [Enstrom F-28C](https://openairdocs.org/model/enstrom-f-28c): 1 cases
- [Ronnie Koonce SAFARI 400](https://openairdocs.org/model/ronnie-koonce-safari-400): 1 cases
- [Buschmann Robert E HELICYCLE](https://openairdocs.org/model/buschmann-robert-e-helicycle): 1 cases
- [Emery Mark ROTORWAY 162F](https://openairdocs.org/model/emery-mark-rotorway-162f): 1 cases

## Other findings in the same cases

- [Scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010) (Personnel issues): 2 cases
- [Decision making/judgment](https://openairdocs.org/ntsb-findings/02041520) (Personnel issues): 2 cases
- [Aircraft control](https://openairdocs.org/ntsb-findings/02063040) (Personnel issues): 1 cases
- [Modification/alteration](https://openairdocs.org/ntsb-findings/02062030) (Personnel issues): 1 cases
- [Scheduled/routine inspection](https://openairdocs.org/ntsb-findings/02061520) (Personnel issues): 1 cases
- [Preflight inspection](https://openairdocs.org/ntsb-findings/02061510) (Personnel issues): 1 cases
- [Lack of action](https://openairdocs.org/ntsb-findings/02041030) (Personnel issues): 1 cases
- [Fuel](https://openairdocs.org/ntsb-findings/01071010) (Aircraft): 1 cases
- [Descent rate](https://openairdocs.org/ntsb-findings/01062037) (Aircraft): 1 cases
- [Yaw control](https://openairdocs.org/ntsb-findings/01062024) (Aircraft): 1 cases

## Newest cases

- [NTSB ANC24LA077](https://openairdocs.org/ntsb/ANC24LA077), Aug 19, 2024: Robinson R44 (N740RH), Honolulu, HI, substantial damage. Probable cause: A failure of the flex plate yoke flange assembly due to incorrectly torqued bolts. Contributing was the maintenance personnel’s inadequate inspection of the tail rotor flex plate assembly.
- [NTSB CEN19LA174](https://openairdocs.org/ntsb/CEN19LA174), Jun 17, 2019: Robinson R44 (N1241W), Key West, FL, substantial damage. Probable cause: The failure of maintenance personnel to properly secure the right-side tail boom mounting bolts which resulted in the failure of the bolts and an inflight separation of the tail rotor.
- [NTSB CEN19LA065](https://openairdocs.org/ntsb/CEN19LA065), Jan 8, 2019: Robinson R44 (N484AB), Uvalde, TX, substantial damage. Probable cause: The slipping of the sprag clutch due to galling of the sprags and corresponding sprag contact surfaces within the clutch assembly, which rendered the helicopter uncontrollable.
- [NTSB CEN18LA247](https://openairdocs.org/ntsb/CEN18LA247), Jul 2, 2018: Safari 400 (N326RW), Aguilares, TX, substantial damage. Probable cause: The loss of tail rotor control due to the in-flight failure of the tail rotor pinion.
- [NTSB CEN15LA379](https://openairdocs.org/ntsb/CEN15LA379), Aug 25, 2015: Robinson Helicopter R44 II (N444KD), Ketchum, OK, substantial damage. Probable cause: The separation of the tail rotor gearbox from the tailboom aft bulkhead due to overstress loads imposed by a blade imbalance from an in-flight impact with an undetermined object.
- [NTSB WPR14LA225](https://openairdocs.org/ntsb/WPR14LA225), Jun 4, 2014: Emery Mark Rotorway 162F (N78291), Merced, CA, destroyed. Probable cause: The helicopter pilot/owner's decision to install a belt type not recommended by the kit manufacturer in the tail rotor drive system using the incorrect tension values, which led to the belt’s…
- [NTSB ERA12LA368](https://openairdocs.org/ntsb/ERA12LA368), May 24, 2012: Schweizer 269C (N760DA), Piney Flats, TN, substantial damage. Probable cause: The mechanic’s improper maintenance of the main transmission aft pinion nut and belt drive system, which resulted in the uncoupling of the tail rotor driveshaft and the subsequent loss of helicopter…
- [NTSB CEN12LA181](https://openairdocs.org/ntsb/CEN12LA181), Mar 5, 2012: Sikorsky 269C (N1099N), Staples, TX, substantial damage. Probable cause: The pilot's failure to attain the proper descent rate during autorotation, which resulted in a hard landing. Contributing to the accident were the inflight vibrations and loss of torque pedal…
- [NTSB CEN11LA414](https://openairdocs.org/ntsb/CEN11LA414), Jun 23, 2011: Enstrom F-28C-2 (N5694A), Blair, NE, substantial damage. Probable cause: The failure of a tail rotor pitch change link due to the retaining bolt becoming separated in flight. Contributing to the accident was the pilot’s inadequate preflight inspection.
- [NTSB NYC08CA252](https://openairdocs.org/ntsb/NYC08CA252), Jul 19, 2008: Buschmann Robert E Helicycle (N3375C), Stuart, FL, substantial damage. Probable cause: The pilot's improper decision to take off with a known discrepancy. Contributing to the accident was spilled fuel on the drive 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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