{
  "name": "Aircraft inspection and test intervals under 14 CFR Part 91",
  "description": "How often each required aircraft inspection, test or check must be done under Part 91, in the unit the regulation actually uses. Each record is one item with its interval, the anchor the interval runs from, and the consequence of letting it lapse. Covers the annual and 100-hour inspection (14 CFR 91.409), the altimeter and static pressure system test (91.411), the ATC transponder test (91.413), the emergency locator transmitter inspection and battery replacement (91.207), and the VOR equipment check for IFR (91.171). Answers 'does an ELT battery have to be replaced every year', 'how often does a transponder need to be checked', 'is the pitot static check 24 months', 'does a 100 hour inspection reset the annual', and 'how often do I need a VOR check for IFR'. Every one of these is expressed in a different unit - 12 calendar months, 100 hours, 24 calendar months, 30 days, 1 cumulative hour of transmitter use or 50 percent of useful life - which is why the neighbouring ones get swapped: the ELT 12-month item is the inspection, not the battery.",
  "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/",
  "licence": "Facts extracted from the US Code of Federal Regulations, a US government work not subject to copyright. Records quote the official eCFR text via its versioner API (the eCFR HTML pages block our fetcher; law.cornell.edu copies were read as a cross-check but carry inline definition links that break verbatim quoting); each record quotes a short verbatim span and links back to the section.",
  "last_verified": "2026-08-06",
  "stale_after": "2028-08-05",
  "sources": [
    "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.409",
    "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.411",
    "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.413",
    "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.207",
    "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.171"
  ],
  "records": [
    {
      "item": "100-hour inspection",
      "interval": "within the preceding 100 hours of time in service",
      "applies_to": "aircraft carrying any person (other than a crewmember) for hire",
      "consequence": "no person may operate an aircraft carrying any person (other than a crewmember) for hire",
      "citation": "\u00a7 91.409",
      "id": "100-hour-inspection",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/100-hour-inspection/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.409",
      "source_quote": "no person may operate an aircraft carrying any person (other than a crewmember) for hire, and no person may give flight instruction for hire in an aircraft which that person provides, unless within the preceding 100 hours of time in service the aircraft has received an annual or 100-hour inspection and been approved for return to service in accordance with part 43 of this chapter or has received an inspection for the issuance of an airworthiness certificate in accordance with part 21 of this chapter. The 100-hour limitation may be exceeded by not more than 10 hours while en route to reach a place where the inspection can be done.",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "Altimeter instrument",
      "interval": "Within the preceding 24 calendar months",
      "applies_to": "airplane, or helicopter, in controlled airspace under IFR",
      "consequence": "No person may operate an airplane, or helicopter, in controlled airspace under IFR",
      "citation": "\u00a7 91.411",
      "id": "altimeter-instrument",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/altimeter-instrument/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.411",
      "source_quote": "No person may operate an airplane, or helicopter, in controlled airspace under IFR unless\u2014 (1) Within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected and found to comply with appendices E and F of part 43 of this chapter;",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "Annual inspection",
      "interval": "within the preceding 12 calendar months",
      "applies_to": "aircraft",
      "consequence": "no person may operate an aircraft",
      "citation": "\u00a7 91.409",
      "id": "annual-inspection",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/annual-inspection/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.409",
      "source_quote": "no person may operate an aircraft unless, within the preceding 12 calendar months, it has had\u2014 (1) An annual inspection in accordance with part 43 of this chapter and has been approved for return to service by a person authorized by \u00a7 43.7 of this chapter",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "ATC transponder",
      "interval": "within the preceding 24 calendar months",
      "applies_to": "ATC transponder that is specified in 91.215(a), 121.345(c), or \u00a7 135.143(c) of this chapter",
      "consequence": "No persons may use an ATC transponder",
      "citation": "\u00a7 91.413",
      "id": "atc-transponder",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/atc-transponder/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.413",
      "source_quote": "No persons may use an ATC transponder that is specified in 91.215(a), 121.345(c), or \u00a7 135.143(c) of this chapter unless, within the preceding 24 calendar months, the ATC transponder has been tested and inspected and found to comply with appendix F of part 43 of this chapter; and",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "Automatic pressure altitude reporting system",
      "interval": "Within the preceding 24 calendar months",
      "applies_to": "airplane, or helicopter, in controlled airspace under IFR",
      "consequence": "No person may operate an airplane, or helicopter, in controlled airspace under IFR",
      "citation": "\u00a7 91.411",
      "id": "automatic-pressure-altitude-reporting-system",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/automatic-pressure-altitude-reporting-system/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.411",
      "source_quote": "No person may operate an airplane, or helicopter, in controlled airspace under IFR unless\u2014 (1) Within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected and found to comply with appendices E and F of part 43 of this chapter;",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "Batteries used in the emergency locator transmitters",
      "interval": "When the transmitter has been in use for more than 1 cumulative hour; or (2) When 50 percent of their useful life (or, for rechargeable batteries, 50 percent of their useful life of charge) has expired",
      "applies_to": "emergency locator transmitters required by paragraphs (a) and (b) of this section",
      "consequence": "must be replaced (or recharged, if the batteries are rechargeable)",
      "citation": "\u00a7 91.207",
      "id": "batteries-used-in-the-emergency-locator-transmitters",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/batteries-used-in-the-emergency-locator-transmitters/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.207",
      "source_quote": "Batteries used in the emergency locator transmitters required by paragraphs (a) and (b) of this section must be replaced (or recharged, if the batteries are rechargeable)\u2014 (1) When the transmitter has been in use for more than 1 cumulative hour; or (2) When 50 percent of their useful life (or, for rechargeable batteries, 50 percent of their useful life of charge) has expired, as established by the transmitter manufacturer under its approval.",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "Emergency locator transmitter",
      "interval": "within 12 calendar months after the last inspection",
      "applies_to": "Each emergency locator transmitter required by paragraph (a) of this section",
      "consequence": "must be inspected within 12 calendar months after the last inspection",
      "citation": "\u00a7 91.207",
      "id": "emergency-locator-transmitter",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/emergency-locator-transmitter/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.207",
      "source_quote": "Each emergency locator transmitter required by paragraph (a) of this section must be inspected within 12 calendar months after the last inspection for\u2014 (1) Proper installation; (2) Battery corrosion; (3) Operation of the controls and crash sensor; and (4) The presence of a sufficient signal radiated from its antenna.",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "Installation or maintenance on an ATC transponder",
      "interval": "Following any installation or maintenance on an ATC transponder where data correspondence error could be introduced",
      "applies_to": "ATC transponder where data correspondence error could be introduced",
      "consequence": "No persons may use an ATC transponder",
      "citation": "\u00a7 91.413",
      "id": "installation-or-maintenance-on-an-atc-transponder",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/installation-or-maintenance-on-an-atc-transponder/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.413",
      "source_quote": "No persons may use an ATC transponder that is specified in 91.215(a), 121.345(c), or \u00a7 135.143(c) of this chapter unless, within the preceding 24 calendar months, the ATC transponder has been tested and inspected and found to comply with appendix F of part 43 of this chapter; and (b) Following any installation or maintenance on an ATC transponder where data correspondence error could be introduced, the integrated system has been tested, inspected, and found to comply with paragraph (c), appendix E, of part 43 of this chapter.",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "Installation or maintenance on the automatic pressure altitude reporting system of the ATC transponder",
      "interval": "Following installation or maintenance on the automatic pressure altitude reporting system of the ATC transponder",
      "applies_to": "airplane, or helicopter, in controlled airspace under IFR",
      "consequence": "No person may operate an airplane, or helicopter, in controlled airspace under IFR",
      "citation": "\u00a7 91.411",
      "id": "installation-or-maintenance-on-the-automatic-pressure-altitude-reporting-system-",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/installation-or-maintenance-on-the-automatic-pressure-altitude-reporting-system-/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.411",
      "source_quote": "No person may operate an airplane, or helicopter, in controlled airspace under IFR unless\u2014 (1) Within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected and found to comply with appendices E and F of part 43 of this chapter; (2) Except for the use of system drain and alternate static pressure valves, following any opening and closing of the static pressure system, that system has been tested and inspected and found to comply with paragraph (a), appendix E, of part 43 of this chapter; and (3) Following installation or maintenance on the automatic pressure altitude reporting system of the ATC transponder where data correspondence error could be introduced, the integrated system has been tested, inspected, and found to comply with paragraph (c), appendix E, of part 43 of this chapter.",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "Opening and closing of the static pressure system",
      "interval": "following any opening and closing of the static pressure system",
      "applies_to": "airplane, or helicopter, in controlled airspace under IFR",
      "consequence": "No person may operate an airplane, or helicopter, in controlled airspace under IFR",
      "citation": "\u00a7 91.411",
      "id": "opening-and-closing-of-the-static-pressure-system",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/opening-and-closing-of-the-static-pressure-system/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.411",
      "source_quote": "No person may operate an airplane, or helicopter, in controlled airspace under IFR unless\u2014 (1) Within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected and found to comply with appendices E and F of part 43 of this chapter; (2) Except for the use of system drain and alternate static pressure valves, following any opening and closing of the static pressure system, that system has been tested and inspected and found to comply with paragraph (a), appendix E, of part 43 of this chapter; and",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "Progressive inspection",
      "interval": "within each 12 calendar months",
      "applies_to": "aircraft",
      "citation": "\u00a7 91.409",
      "id": "progressive-inspection",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/progressive-inspection/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.409",
      "source_quote": "The frequency and detail of the progressive inspection shall provide for the complete inspection of the aircraft within each 12 calendar months and be consistent with the manufacturer's recommendations, field service experience, and the kind of operation in which the aircraft is engaged.",
      "verified_fields": [
        "applies_to",
        "citation",
        "interval",
        "item"
      ]
    },
    {
      "item": "Static pressure system",
      "interval": "Within the preceding 24 calendar months",
      "applies_to": "airplane, or helicopter, in controlled airspace under IFR",
      "consequence": "No person may operate an airplane, or helicopter, in controlled airspace under IFR",
      "citation": "\u00a7 91.411",
      "id": "static-pressure-system",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/static-pressure-system/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.411",
      "source_quote": "No person may operate an airplane, or helicopter, in controlled airspace under IFR unless\u2014 (1) Within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected and found to comply with appendices E and F of part 43 of this chapter;",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    },
    {
      "item": "VOR equipment",
      "interval": "within the preceding 30 days",
      "applies_to": "civil aircraft under IFR using the VOR system of radio navigation",
      "consequence": "No person may operate a civil aircraft under IFR",
      "citation": "\u00a7 91.171",
      "id": "vor-equipment",
      "url": "https://referencesource.org/aircraft-inspection-and-test-intervals/vor-equipment/",
      "source": "https://www.ecfr.gov/api/versioner/v1/full/2026-08-01/title-14.xml?part=91&section=91.171",
      "source_quote": "No person may operate a civil aircraft under IFR using the VOR system of radio navigation unless the VOR equipment of that aircraft\u2014 (1) Is maintained, checked, and inspected under an approved procedure; or (2) Has been operationally checked within the preceding 30 days, and was found to be within the limits of the permissible indicated bearing error set forth in paragraph (b) or (c) of this section.",
      "verified_fields": [
        "applies_to",
        "citation",
        "consequence",
        "interval",
        "item"
      ]
    }
  ]
}