# Ground resonance

- Type: NTSB defining event
- NTSB code: 232
- CICTT category: Loss Of Control (Ground)
- Defining event in: 19 cases
- In the sequence of: 21 cases
- Fatal cases: 0
- All cases: https://openairdocs.org/ntsb-events/232/cases.md
- Cases with it anywhere in the sequence: https://openairdocs.org/ntsb-events/232/sequence.md
- Page: https://openairdocs.org/ntsb-events/232

## Cases per year (defining / in the sequence)

- 2008: 1 / 1
- 2009: 1 / 1
- 2010: 0 / 1
- 2011: 2 / 2
- 2012: 4 / 4
- 2014: 3 / 3
- 2016: 1 / 1
- 2017: 1 / 1
- 2018: 1 / 1
- 2019: 1 / 1
- 2021: 0 / 1
- 2023: 2 / 2
- 2024: 1 / 1
- 2025: 1 / 1

## Phase of flight

- Landing: 7 cases
- Standing-engine(s) operating: 7 cases
- Takeoff: 4 cases
- Standing-engine(s) start-up: 1 cases

## In the probable cause of these cases

- [Aircraft control](https://openairdocs.org/ntsb-findings/02063040) (Personnel issues): 6 cases
- [Main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213) (Aircraft): 5 cases
- [Maintenance records](https://openairdocs.org/ntsb-findings/04033025) (Organizational issues): 2 cases
- [Oversight of personnel](https://openairdocs.org/ntsb-findings/04032010) (Organizational issues): 2 cases
- [Use of equip/system](https://openairdocs.org/ntsb-findings/02063015) (Personnel issues): 2 cases
- [Scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010) (Personnel issues): 2 cases
- [Maintenance, general](https://openairdocs.org/ntsb-findings/02062000) (Personnel issues): 2 cases
- [Incorrect action performance](https://openairdocs.org/ntsb-findings/02041015) (Personnel issues): 2 cases
- [Aux gear (tail/rotorcrft skid)](https://openairdocs.org/ntsb-findings/01023270) (Aircraft): 2 cases
- [Use of policy/procedure](https://openairdocs.org/ntsb-findings/02063032) (Personnel issues): 1 cases

## Aircraft models (registry)

- [Schweizer 269C](https://openairdocs.org/model/schweizer-269c): 6 cases
- [Schweizer 269C-1](https://openairdocs.org/model/schweizer-269c-1): 4 cases
- [Hughes 269A](https://openairdocs.org/model/hughes-269a): 3 cases
- [Eurocopter AS 350 B3](https://openairdocs.org/model/eurocopter-as-350-b3): 1 cases
- [Hughes 269C](https://openairdocs.org/model/hughes-269c): 1 cases
- [Hughes 269B](https://openairdocs.org/model/hughes-269b): 1 cases
- [Bell Textron Canada 505](https://openairdocs.org/model/bell-textron-canada-505): 1 cases
- [American Eurocopter AS350B3](https://openairdocs.org/model/american-eurocopter-as350b3): 1 cases
- [Agusta A109E](https://openairdocs.org/model/agusta-a109e): 1 cases

## Newest cases

- [NTSB ERA25LA255](https://openairdocs.org/ntsb/ERA25LA255), Jul 2, 2025: Schweizer 269C (N21385), Madisonville, KY, substantial damage. Probable cause: The pilot’s failure to take the appropriate corrective action for ground resonance, which resulted in a loss of helicopter control.
- [NTSB ERA24LA399](https://openairdocs.org/ntsb/ERA24LA399), Aug 23, 2024: Bell Textron Canada 505 (N945TC), Marianna, FL, substantial damage. Probable cause: The 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…
- [NTSB ERA23LA284](https://openairdocs.org/ntsb/ERA23LA284), Jul 1, 2023: Schweizer 269C (N9WZ), Macclenny, FL, substantial damage. Probable cause: The 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…
- [NTSB ERA23LA289](https://openairdocs.org/ntsb/ERA23LA289), Jun 27, 2023: Hughes 269A (N90270), Anderson, SC, substantial damage. Probable cause: The mechanics’ improper torquing of the main rotor blade dampers, which resulted in a ground resonance event during landing.
- [NTSB ERA19LA173](https://openairdocs.org/ntsb/ERA19LA173), May 15, 2019: Hughes 269B (N9422F), Hampton, GA, substantial damage. Probable cause: Ground resonance during landing for reasons that could not be determined based on the available information.
- [NTSB WPR18LA170](https://openairdocs.org/ntsb/WPR18LA170), Jun 13, 2018: Schweizer 269C (N557DC), Las Vegas, NV, substantial damage. Probable cause: The pilot’s failure to take the appropriate corrective action for ground resonance, which resulted in a loss of helicopter control.
- [NTSB CEN17LA229](https://openairdocs.org/ntsb/CEN17LA229), Jun 10, 2017: Hughes 269C (N7482F), Tallulah, LA, substantial damage. Probable cause: The pilot's failure to reset the cyclic trim before takeoff, which resulted in ground resonance.
- [NTSB ERA16LA261](https://openairdocs.org/ntsb/ERA16LA261), Jul 16, 2016: Schweizer 269C (N6148D), Calhoun, GA, substantial damage. Probable cause: The 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…
- [NTSB ERA14LA293](https://openairdocs.org/ntsb/ERA14LA293), Jun 17, 2014: Schweizer 269C-1 (N152CC), Allentown, PA, substantial damage. Probable cause: Inadequate inspection and maintenance of the helicopter’s landing gear dampers, which resulted in ground resonance during helicopter shutdown.
- [NTSB ANC14LA041](https://openairdocs.org/ntsb/ANC14LA041), Jun 11, 2014: Airbus/Eurocopter AS 350 B3 (N356EV), Anchorage, AK, substantial damage. Probable cause: The pilot’s improper engine start procedure, which resulted in an overspeed of the engine and main rotor drive system.

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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