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Ground resonance

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NTSB defining event · CICTT: Loss Of Control (Ground)

CICTT occurrence categories (PDF)CICTT phases of flight (PDF)

All 19 cases21 anywhere in the sequence
Defining event in
19 cases
In the sequence of
21 cases
Fatal cases
0
NTSB code
232

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 it was the defining event; in gray, cases where it came elsewhere in the sequence. The map shows the cases where it was the defining event. Events are coded with the final report, so the latest years are incomplete.

Cases per year

2008Defining eventElsewhere in the sequence2026

Where

Open the map
Query with SQL
duckdb -csv -c "SELECT year(c.\"eventDate\") AS year, count(DISTINCT e.case_mkey) AS cases,
    count(DISTINCT e.case_mkey) FILTER (WHERE e.\"isDefiningEvent\") AS defining
  FROM 'https://openairdocs.org/data/latest/ntsb_events.parquet' e JOIN 'https://openairdocs.org/data/latest/ntsb_case_detail.parquet' c ON c.\"mKey\" = e.case_mkey
  WHERE e.\"tier2Number\" = '232' AND e.case_mkey IN (SELECT case_mkey FROM 'https://openairdocs.org/data/latest/ntsb_events.parquet' WHERE \"isDefiningEvent\")
  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 these cases

Phase of flight
  • Landing7
  • Standing-engine(s) operating7
  • Takeoff4
  • Standing-engine(s) start-up1
In the probable cause
Aircraft models

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

Query with SQL
duckdb -csv -c "WITH defining AS (SELECT * FROM 'https://openairdocs.org/data/latest/ntsb_events.parquet' WHERE \"tier2Number\" = '232' AND \"isDefiningEvent\")
  SELECT * FROM (
  SELECT 'Phase of flight' AS kind, e.\"tier1Number\" AS code, max(e.\"eventTier1Name\") AS name, count(DISTINCT e.case_mkey) AS cases
  FROM defining e
  GROUP BY ALL
  UNION ALL
  SELECT 'Finding in the probable cause', left(f.\"findingCode\", 8), max(f.\"tier4Name\"), count(DISTINCT f.case_mkey)
  FROM defining e JOIN 'https://openairdocs.org/data/latest/ntsb_findings.parquet' f ON f.case_mkey = e.case_mkey AND f.aircrafts_position = e.aircrafts_position AND f.\"inProbableCause\"
  WHERE f.\"findingCode\" GLOB '[0-9][0-9]*'
  GROUP BY ALL
  UNION ALL
  SELECT 'Aircraft model', a.aircraft_model_code, any_value(concat_ws(' ', m.manufacturer, m.model)), count(DISTINCT e.case_mkey)
  FROM defining e JOIN 'https://openairdocs.org/data/latest/ntsb_aircrafts.parquet' a ON a.case_mkey = e.case_mkey AND a.position = e.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
  )
  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 · 19

NTSB ERA25LA255Accident · Minor injuriesClass 4 · LimitedFinal reportSchweizer 269C · Madisonville, KYThe pilot’s failure to take the appropriate corrective action for ground resonance, which resulted in a loss of helicopter control.Jul 2, 2025 · N21385 · Substantial damageNTSB ERA24LA399Accident · No injuriesClass 3 · LimitedFinal reportBell Textron Canada 505 · Marianna, FLThe student pilot’s failure to maintain rotor rpm during a simulated autorotation, which allowed for a resonance phenomenon to develop. Contributing to the accident was the flight instructor’s inadequate monitoring of the student pilot’s collective control…Aug 23, 2024 · N945TC · Substantial damageNTSB ERA23LA284Accident · Minor injuriesClass 3 · LimitedFinal reportSchweizer 269C · Macclenny, FLThe improper maintenance of the landing gear dampers and main rotor elastomeric dampers, resulting in ground resonance during an unsuccessful takeoff attempt with the helicopter near its maximum gross weight for the density altitude.Jul 1, 2023 · N9WZ · Substantial damageNTSB ERA23LA289Accident · No injuriesClass 4 · LimitedFinal reportHughes 269A · Anderson, SCThe mechanics’ improper torquing of the main rotor blade dampers, which resulted in a ground resonance event during landing.Jun 27, 2023 · N90270 · Substantial damageNTSB ERA19LA173Accident · No injuriesClass 3 · LimitedFinal reportHughes 269B · Hampton, GAGround resonance during landing for reasons that could not be determined based on the available information.May 15, 2019 · N9422F · Substantial damageNTSB WPR18LA170Accident · Minor injuriesClass 3 · LimitedFinal reportSchweizer 269C · Las Vegas, NVThe pilot’s failure to take the appropriate corrective action for ground resonance, which resulted in a loss of helicopter control.Jun 13, 2018 · N557DC · Substantial damageNTSB CEN17LA229Accident · No injuriesLimited investigationFinal reportHughes 269C · Tallulah, LAThe pilot's failure to reset the cyclic trim before takeoff, which resulted in ground resonance.Jun 10, 2017 · N7482F · Substantial damageNTSB ERA16LA261Accident · No injuriesLimited investigationFinal reportSchweizer 269C · Calhoun, GAThe helicopter owner’s failure to ensure the helicopter’s airworthiness and the inadequate inspection and maintenance of the helicopter's landing gear dampers, which resulted in ground resonance during throttle application. Contributing to the damage of the…Jul 16, 2016 · N6148D · Substantial damageNTSB ERA14LA293Accident · Minor injuriesLimited investigationFinal reportSchweizer 269C-1 · Allentown, PAInadequate inspection and maintenance of the helicopter’s landing gear dampers, which resulted in ground resonance during helicopter shutdown.Jun 17, 2014 · N152CC · Substantial damageNTSB ANC14LA041Accident · No injuriesClass 3 · LimitedFinal reportAirbus/Eurocopter AS 350 B3 · Anchorage, AKThe pilot’s improper engine start procedure, which resulted in an overspeed of the engine and main rotor drive system.Jun 11, 2014 · N356EV · Substantial damage
See all 19 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 e.case_mkey FROM 'https://openairdocs.org/data/latest/ntsb_events.parquet' e WHERE e.\"isDefiningEvent\" AND e.\"tier2Number\" = '232')
  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.