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Tail rotor gearbox

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NTSB finding · Aircraft › Aircraft propeller/rotor › Tail rotor drive system

All 12 cases
Cases
12
In the probable cause
12 (100%)
Fatal cases
1
NTSB code
01046520

NTSB has coded findings and defining events since 2008. Earlier cases used its older occurrence and cause codes, so they aren’t counted here.

When and where

In green, cases where NTSB made it part of the probable cause; in gray, a factor or other finding. Findings are coded with the final report, often a year or more after the event, so the latest years are incomplete.

Cases per year

2008In the probable causeFactor only2026

Where

Open the map
Query with SQL
duckdb -csv -c "SELECT year(c.\"eventDate\") AS year, count(DISTINCT f.case_mkey) AS cases,
    count(DISTINCT f.case_mkey) FILTER (WHERE f.\"inProbableCause\") AS in_probable_cause
  FROM 'https://openairdocs.org/data/latest/ntsb_findings.parquet' f JOIN 'https://openairdocs.org/data/latest/ntsb_case_detail.parquet' c ON c.\"mKey\" = f.case_mkey
  WHERE starts_with(f.\"findingCode\", '01046520') AND c.\"eventDate\" >= DATE '2000-01-01'
  GROUP BY 1
  ORDER BY 1"

Prints the counts as CSV. It reads the release’s Parquet files over HTTPS, so there’s nothing to download first. Install DuckDB to run it.

In the same cases

Defining events
Aircraft models

Aircraft matched to the registry by N-number and date.

Other findings
Query with SQL
duckdb -csv -c "WITH matched AS (SELECT DISTINCT case_mkey, aircrafts_position FROM 'https://openairdocs.org/data/latest/ntsb_findings.parquet' WHERE starts_with(\"findingCode\", '01046520'))
  SELECT * FROM (
  SELECT 'Defining event' AS kind, e.\"tier2Number\" AS code, max(e.\"eventTier2Name\") AS name, count(DISTINCT f.case_mkey) AS cases
  FROM matched f JOIN 'https://openairdocs.org/data/latest/ntsb_events.parquet' e ON e.case_mkey = f.case_mkey AND e.aircrafts_position = f.aircrafts_position AND e.\"isDefiningEvent\"
  WHERE e.\"tier2Number\" <> ''
  GROUP BY ALL
  UNION ALL
  SELECT 'Aircraft model', a.aircraft_model_code, any_value(concat_ws(' ', m.manufacturer, m.model)), count(DISTINCT f.case_mkey)
  FROM matched f JOIN 'https://openairdocs.org/data/latest/ntsb_aircrafts.parquet' a ON a.case_mkey = f.case_mkey AND a.position = f.aircrafts_position
  LEFT JOIN 'https://openairdocs.org/data/latest/faa_aircraft_model.parquet' m ON m.code = a.aircraft_model_code
  WHERE a.aircraft_model_code IS NOT NULL
  GROUP BY ALL
  UNION ALL
  SELECT 'Other finding', left(g.\"findingCode\", 8), max(g.\"tier4Name\"), count(DISTINCT g.case_mkey)
  FROM 'https://openairdocs.org/data/latest/ntsb_findings.parquet' g
  WHERE g.case_mkey IN (SELECT case_mkey FROM matched) AND NOT starts_with(g.\"findingCode\", '01046520') AND g.\"findingCode\" GLOB '[0-9][0-9]*'
  GROUP BY ALL
  )
  QUALIFY row_number() OVER (PARTITION BY kind ORDER BY cases DESC) <= 10
  ORDER BY kind, cases DESC"

Prints the counts as CSV. It reads the release’s Parquet files over HTTPS, so there’s nothing to download first. Install DuckDB to run it.

Newest cases · 12

NTSB WPR22LA084Accident · No injuriesClass 3 · LimitedFinal reportBell UH-1E · Gustine, CAFailure of the 90° gearbox due to the lack of lubricating oil, which resulted in a loss of rotational drive to the tail rotor and a subsequent loss of control of the helicopter.Jan 23, 2022 · N333XL · Substantial damageNTSB ERA21LA386Accident · Minor injuriesClass 3 · LimitedFinal reportHiller UH-12E · Millen, GAThe improper reassembly of the tail rotor gearbox following maintenance, which resulted in fatigue failure of the input pinion gear shaft, and the subsequent loss of tail rotor drive.Sep 29, 2021 · N430NR · Substantial damageNTSB ERA20LA310Accident · No injuriesClass 3 · LimitedFinal reportRobinson R22 · Fort Myers, FLForeign object damage of the turning tailrotor by a soft-bodied object, which resulted in the sudden stoppage of the tailrotor and the catastrophic failure of the tailrotor assembly and its mount structure.Sep 6, 2020 · N194HC · Substantial damageNTSB WPR17LA002Accident · Minor injuriesLimited investigationFinal reportTamarack Helicopters UH-1H · Gila Bend, AZThe separation of the 90° tail rotor gearbox assembly as a result of fatigue to the tail rotor gearbox input quill assembly attachment studs due to the helicopter experiencing highly repetitive agricultural flight profiles for which it was not designed.Oct 5, 2016 · N175SF · Substantial damageNTSB ANC15LA073Accident · No injuriesLimited investigationFinal reportRobinson Helicopter R44 · Fort Glenn, AKThe separation of the tail rotor gearbox from the tailboom attachment point due to overstress loads imposed by a tail rotor blade imbalance as the result of impact with an undetermined object during low-level flight operations.Sep 19, 2015 · N7162R · Substantial damageNTSB CEN15LA379Accident · Minor injuriesLimited investigationFinal reportRobinson Helicopter R44 II · Ketchum, OKThe 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.Aug 25, 2015 · N444KD · Substantial damageNTSB ANC13TA076Accident · No injuriesFinal reportBell UH-1B · Tok, AKThe failure of the tail rotor crosshead bearing, which resulted in a loss of tail rotor control.Aug 8, 2013 · N70NW · Substantial damageNTSB CEN13FA192Accident · 3 fatalField investigationFinal reportSikorsky S-76A++ · Grand Lake, LAFracture of the red tail rotor blade spar, which resulted in the separation and departure of the red tail rotor blade from the helicopter and subsequent compromised tail gearbox. The red tail rotor blade was not recovered, thus the cause of the initial…Mar 15, 2013 · N574EH · DestroyedNTSB WPR13FA006Accident · Minor injuriesField investigationFinal reportGarlick Helicopters UH-1H · Shady Cove, ORThe separation of the tail rotor gearbox and tail rotor assembly as a result of fatigue to the tail rotor gearbox input quill assembly attachment studs.Oct 7, 2012 · N1577 · Substantial damageNTSB CEN12LA120Accident · Serious injuriesLimited investigationFinal reportContinental Copters 47G2 · Lohn, TXThe improper installation of the tail rotor gearbox by maintenance personnel, which led to accelerated wear of the ring and pinion gears, resulting in the loss of tail rotor effectiveness and subsequent forced landing.Jan 1, 2012 · N9021R · Substantial damage
See all 12 cases
Query with SQL
duckdb -csv -c "SELECT c.\"ntsbNumber\", c.\"eventDate\", c.\"eventType\", c.\"eventCity\", c.\"eventStateOrRegion\", a.n_number, a.\"aircraftMake\", a.\"aircraftModel\", c.\"highestInjuryLevel\", c.\"totalFatal\", c.\"completionStatus\", c.report_url
  FROM 'https://openairdocs.org/data/latest/ntsb_case_detail.parquet' c LEFT JOIN 'https://openairdocs.org/data/latest/ntsb_aircrafts.parquet' a ON a.case_mkey = c.\"mKey\" AND a.position = 1
  WHERE c.\"mKey\" IN (SELECT f.case_mkey FROM 'https://openairdocs.org/data/latest/ntsb_findings.parquet' f WHERE starts_with(f.\"findingCode\", '01046520'))
  ORDER BY c.\"eventDate\" DESC, c.\"ntsbNumber\" DESC"

Prints the whole list as CSV. It reads the release’s Parquet files over HTTPS, so there’s nothing to download first. Install DuckDB to run it.