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Master cylinder/brake valve

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NTSB finding · Aircraft › Aircraft systems › Landing gear system

All 21 cases20 in the probable cause
Cases
21
In the probable cause
20 (95%)
Fatal cases
0
NTSB code
01023243

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\", '01023243') 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\", '01023243'))
  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\", '01023243') 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 · 21

NTSB CEN25LA264Accident · No injuriesClass 4 · LimitedFinal reportAlon A2 · Pipestone, MNThe failure of the left brake to release due to corrosion and pitting of the caliper piston and bore, which resulted in a runway excursion.Jul 20, 2025 · N6557Q · Substantial damageNTSB WPR24LA045Accident · Minor injuriesClass 3 · LimitedFinal reportCessna 170B · Cameron Park, CAA failure of the right brake master cylinder piston due to a faulty return spring, which resulted in a seized right main landing gear brake and a runway excursionNov 27, 2023 · N170HT · Substantial damageNTSB WPR22LA324Accident · No injuriesClass 3 · LimitedFinal reportChampion 7GCBA · Athol, IDThe failure of the right brake due to a disconnected master cylinder piston rod, which led to the departure of the airplane from the runway surface. Contributing to the accident was the mechanic’s failure to adequately inspect the connection between the…Aug 23, 2022 · N9512S · Substantial damageNTSB ERA22LA132Accident · No injuriesClass 4 · LimitedFinal reportCessna 140 · New Bern, NCThe loss of brake pressure on the left brake due to a failed O-ring seal.Feb 11, 2022 · N2509N · Substantial damageNTSB ERA21LA044Accident · No injuriesClass 4 · LimitedFinal reportCessna 305 · Ellenville, NYThe failure of the right brake master cylinder lock seal spring washer.Nov 14, 2020 · N5179G · Substantial damageNTSB GAA18CA022Accident · No injuriesData collectionFinal reportAviat A1 · Williamsport, PAThe pilot’s failure to verify that the parking brake was disengaged before landing, which resulted in a runway excursion.Oct 22, 2017 · N337AM · Substantial damageNTSB WPR18LA009Accident · No injuriesLimited investigationFinal reportBarber Warren D Turbine Cubs P A 18 · Skull Valley, UTThe activation of the wheel brakes during landing, which resulted in a nose-over. The reason for the wheel brake activation could not be determined.Oct 15, 2017 · N181TJ · Substantial damageNTSB ERA17LA290Accident · No injuriesLimited investigationFinal reportCessna 180 · Newport, NHA leak in the right brake slave cylinder, which led to no fluid in the reservoir and subsequent asymmetric braking.Aug 20, 2017 · N1585C · Substantial damageNTSB GAA17CA212Accident · No injuriesData collectionFinal reportThomas Craig E Wittman W-10 · Stevensville, MTThe pilot’s decision to take off with a known master brake cylinder leak and his subsequent failure to maintain directional control during landing.Mar 28, 2017 · N13XZ · Substantial damageNTSB ANC17LA005Accident · No injuriesLimited investigationFinal reportCessna A185 · Ninilchik, AKA loss of brake system fluid due to leaks in the o-rings, which resulted in asymmetrical braking and a subsequent loss of directional control during the landing roll.Nov 12, 2016 · N4918Q · Substantial damage
See all 21 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\", '01023243'))
  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.