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Understanding Required Aircraft Maintenance Inspections

Updated: Dec 19

Aircraft maintenance inspections are the backbone of aviation safety. Whether you’re a private pilot, aircraft owner, or aviation enthusiast, understanding required inspections helps ensure compliance with regulations and, more importantly, keeps flights safe and reliable. In the United States, the FAA mandates several recurring inspections depending on how an aircraft is operated and equipped.


Below is an overview of the most common required maintenance inspections: Annual, 100-Hour, VOR, Altimeter, Transponder, ELT, and Static System inspections.



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Annual Inspection

The annual inspection is the most comprehensive routine inspection required for most civil aircraft.

  • Who needs it?

    • All FAA-registered aircraft, regardless of how often they fly.

  • Frequency:

    • Every 12 calendar months.

  • Who can perform it?

    • An A&P mechanic with Inspection Authorization (IA).

  • What it covers:

    • A thorough inspection of the entire aircraft—airframe, engine, propeller, systems, and components—using a checklist defined by the FAA and manufacturer.


An aircraft that fails an annual inspection is not airworthy until all discrepancies are corrected and signed off.


100-Hour Inspection

The 100-hour inspection applies primarily to aircraft used for hire.

  • Who needs it?

    • Aircraft used for flight instruction or carrying passengers for hire.

  • Frequency:

    • Every 100 hours of time in service.

  • Who can perform it?

    • A certified A&P mechanic (IA not required).

  • Key difference from an annual:

    • The scope is nearly identical to an annual inspection, but it does not replace the annual unless performed by an IA and signed off as an annual.


This inspection ensures aircraft used more intensively receive frequent checks.


VOR Inspection

The VOR (VHF Omnidirectional Range) inspection ensures navigation accuracy for IFR operations.

  • Who needs it?

    • Aircraft flown under IFR using VOR equipment.

  • Frequency:

    • Every 30 days.

  • What’s checked:

    • VOR accuracy using ground checkpoints, airborne checkpoints, or test facilities.

  • Documentation:

    • Results must be logged, including date, error, location, and signature.


Without a current VOR check, an aircraft cannot legally fly IFR using VOR navigation.


Altimeter Inspection

The altimeter inspection verifies accurate altitude reporting.

  • Who needs it?

    • Aircraft operating in controlled airspace under IFR.

  • Frequency:

    • Every 24 calendar months.

  • What’s included:

    • Altimeter accuracy, pressure settings, and compliance with tolerances.


This inspection is typically performed alongside static system checks.


Transponder Inspection

The transponder inspection ensures accurate aircraft identification and altitude reporting to air traffic control.

  • Who needs it?

    • Aircraft operating in Class A, B, or C airspace, or above 10,000 feet MSL.

  • Frequency:

    • Every 24 calendar months.

  • What’s checked:

    • Transponder reply accuracy, Mode C altitude reporting, and system integrity.


A failed transponder inspection can restrict where and how an aircraft may be flown.


ELT Inspection

The Emergency Locator Transmitter (ELT) is critical for post-accident search and rescue.

  • Who needs it?

    • Most civil aircraft.

  • Frequency:

    • Every 12 calendar months

    • After one cumulative hour of use

    • When the battery expires (or reaches 50% of useful life)

  • What’s checked:

    • Proper operation, mounting, antenna condition, and battery status.


A functioning ELT can dramatically reduce rescue times in an emergency.


Static System Inspection

The static system inspection ensures accurate airspeed, altitude, and vertical speed indications.

  • Who needs it?

    • Aircraft flown under IFR.

  • Frequency:

    • Every 24 calendar months.

  • What’s included:

    • Leak testing of the static system, ensuring pressure integrity and accuracy.


Because multiple instruments rely on static pressure, this inspection is essential for safe IFR flight.


Staying Compliant and Airworthy

Keeping track of inspections is a key responsibility for aircraft owners and operators. Missing an inspection can ground an aircraft or limit its legal operation, especially in IFR or controlled airspace. Many pilots use maintenance tracking software or detailed logbook reviews to stay ahead of inspection deadlines.


Ultimately, these inspections are more than regulatory checkboxes—they’re proven safety measures that protect pilots, passengers, and aircraft alike.



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