# Hydraulic, main system

- Type: NTSB finding subsection
- Path: [Aircraft](https://openairdocs.org/ntsb-findings/01) › [Aircraft systems](https://openairdocs.org/ntsb-findings/0102) › [Hydraulic power system](https://openairdocs.org/ntsb-findings/010229) › Hydraulic, main system
- NTSB code: 01022910
- Cases: 29
- In the probable cause: 24
- Fatal cases: 3
- All cases: https://openairdocs.org/ntsb-findings/01022910/cases.md
- Cases with it in the probable cause: https://openairdocs.org/ntsb-findings/01022910/cases.md?cause=1
- Page: https://openairdocs.org/ntsb-findings/01022910

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

- 2008: 1 / 1
- 2009: 2 / 2
- 2010: 2 / 2
- 2011: 1 / 2
- 2012: 3 / 3
- 2014: 3 / 5
- 2015: 1 / 1
- 2016: 1 / 1
- 2017: 2 / 2
- 2018: 1 / 1
- 2019: 1 / 1
- 2020: 1 / 1
- 2021: 1 / 1
- 2022: 1 / 1
- 2023: 1 / 2
- 2024: 1 / 1
- 2026: 1 / 2

## Defining events in these cases

- [Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330): 11 cases
- [Loss of control in flight](https://openairdocs.org/ntsb-events/240): 6 cases
- [Landing gear collapse](https://openairdocs.org/ntsb-events/094): 6 cases
- [Runway excursion](https://openairdocs.org/ntsb-events/300): 2 cases
- [Birdstrike](https://openairdocs.org/ntsb-events/901): 1 cases
- [Landing gear not configured](https://openairdocs.org/ntsb-events/095): 1 cases
- [Abnormal runway contact](https://openairdocs.org/ntsb-events/090): 1 cases
- [Preflight or dispatch event](https://openairdocs.org/ntsb-events/030): 1 cases

## Aircraft models (registry)

- [Eurocopter AS 350 B2](https://openairdocs.org/model/eurocopter-as-350-b2): 3 cases
- [Fairchild SA227-AC](https://openairdocs.org/model/fairchild-sa227-ac): 2 cases
- [Sikorsky S55B](https://openairdocs.org/model/sikorsky-s55b): 1 cases
- [Rockwell International 112](https://openairdocs.org/model/rockwell-international-112): 1 cases
- [Raytheon HAWKER 800XP](https://openairdocs.org/model/raytheon-hawker-800xp): 1 cases
- [Piper PA-31-350](https://openairdocs.org/model/piper-pa-31-350): 1 cases
- [Piper PA-23-250](https://openairdocs.org/model/piper-pa-23-250): 1 cases
- [Piaggio Aero Industries P180](https://openairdocs.org/model/piaggio-aero-industries-p180): 1 cases
- [Lockheed SP-2H](https://openairdocs.org/model/lockheed-sp-2h): 1 cases
- [Lockheed P2V-5](https://openairdocs.org/model/lockheed-p2v-5): 1 cases

## Other findings in the same cases

- [Decision making/judgment](https://openairdocs.org/ntsb-findings/02041520) (Personnel issues): 4 cases
- [Gear extension and retract sys](https://openairdocs.org/ntsb-findings/01023230) (Aircraft): 4 cases
- [Not determined, general](https://openairdocs.org/ntsb-findings/05000000) (Not determined): 3 cases
- [Use of equip/system](https://openairdocs.org/ntsb-findings/02063015) (Personnel issues): 3 cases
- [Incorrect action performance](https://openairdocs.org/ntsb-findings/02041015) (Personnel issues): 3 cases
- [Aircraft control](https://openairdocs.org/ntsb-findings/02063040) (Personnel issues): 2 cases
- [Scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010) (Personnel issues): 2 cases
- [Action, general](https://openairdocs.org/ntsb-findings/02041000) (Personnel issues): 2 cases
- [Hydraulic fluid](https://openairdocs.org/ntsb-findings/01071015) (Aircraft): 2 cases
- [Airspeed](https://openairdocs.org/ntsb-findings/01062010) (Aircraft): 2 cases

## Newest cases

- [NTSB WPR26LA343](https://openairdocs.org/ntsb/WPR26LA343), Sep 12, 2026: Aerovodochody L-29 Delfin (N29AD), Roswell, NM, substantial damage. Probable cause: The malfunction of a diode in the airplanes electrical system that resulted in low batter power and subsequent landing gear collapse.
- [NTSB DCA26LA151](https://openairdocs.org/ntsb/DCA26LA151), Mar 7, 2026: Fairchild SA227-AC (N425MA), Denver, CO, substantial damage. Probable cause: The overstress failure of the left main landing gear lower drag brace links during takeoff which resulted in a runway excursion during landing due to the left main landing gear collapsing.
- [NTSB DCA24LA095](https://openairdocs.org/ntsb/DCA24LA095), Feb 11, 2024: Boeing 737-823 (N991AN), Dallas, TX, incident, minor damage. Probable cause: Improper maintenance due to human error during a braking system modification diminished braking performance. Contributing to the diminished braking performance was the lack of a functional check to…
- [NTSB DCA24FA002](https://openairdocs.org/ntsb/DCA24FA002), Oct 5, 2023: Boeing 757-236 (N977FD), Chattanooga, TN, substantial damage. Probable cause: The failure of the alternate gear extension system, which prevented the landing gear from being lowered. The cause of the system failure was a broken wire, due to tensile overload, between the…
- [NTSB ERA23LA202](https://openairdocs.org/ntsb/ERA23LA202), Apr 18, 2023: Rockwell International 112 (N12RX), Miami, FL, substantial damage. Probable cause: Failure of the right main landing gear due to inadequate hydraulic pressure as result of a torn O-ring that was installed on the hydraulic pack’s check valve during overhaul.
- [NTSB WPR22LA341](https://openairdocs.org/ntsb/WPR22LA341), Sep 7, 2022: Cessna 750 (N15TZ), Mesa, AZ, substantial damage. Probable cause: The pilot’s improper decision to depart on the accident flight with a known hydraulic leak, resulting in an in-flight hydraulic system failure, and the pilot’s attempt to land during an unstabilized…
- [NTSB DCA21LA229](https://openairdocs.org/ntsb/DCA21LA229), Sep 1, 2021: Boeing 767-332 (N196DN), Seattle, WA, no damage. Probable cause: The flightcrew’s failure to set the hydraulic panel correctly during the execution of the pushback checklist, and when the hydraulic panel setting was corrected, that resulted in the airplane coming…
- [NTSB WPR20LA280](https://openairdocs.org/ntsb/WPR20LA280), Aug 19, 2020: Arrow-Falcon Exporters UH-1H (N711GH), Coalinga, CA, destroyed, 1 fatal. Probable cause: The pilot’s inability to maintain control of the helicopter due to a hydraulic system failure for reasons that could not be fully determined due to the thermal destruction from the postimpact fire.
- [NTSB CEN19LA246](https://openairdocs.org/ntsb/CEN19LA246), Jul 27, 2019: Swearingen SA227 (N681TR), El Paso, TX, substantial damage. Probable cause: Failure of the left main landing gear to fully extend due to a lack of hydraulic fluid and during emergency extension procedures, which resulted in the collapse of the landing gear during landing and…
- [NTSB ERA18LA067](https://openairdocs.org/ntsb/ERA18LA067), Jan 21, 2018: Cessna 172RG (N9415B), Martinsburg, WV, substantial damage. Probable cause: A hydraulic leak in the right main landing gear actuator, which resulted in the main landing gear not extending.

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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