What Is an Airworthiness Directive (AD) and How Do I Check Compliance?

Airworthiness Directives — universally called ADs in aviation — are legally mandatory maintenance requirements issued by the FAA when an unsafe condition is found in an aircraft, engine, propeller, or component. They are not optional. An aircraft that has not complied with all applicable ADs is not legally airworthy, and operating it is a violation of FAA regulations.

For aircraft owners, understanding ADs is a fundamental responsibility of ownership. This guide explains what ADs are, how they work, and how to ensure your aircraft is in compliance.

What Triggers an Airworthiness Directive?

The FAA issues ADs in response to identified safety problems. The trigger is usually one of the following:

Service difficulty reports: When mechanics discover a recurring problem across multiple aircraft of the same type, they file reports with the FAA. A pattern of similar failures can prompt an AD.

Accident and incident investigations: When the NTSB or FAA investigates an accident and identifies a contributing mechanical factor, an AD may follow to address the issue fleet-wide.

Manufacturer service bulletins: Aircraft manufacturers regularly issue service bulletins recommending maintenance or modifications. When the FAA determines that a manufacturer's service bulletin addresses a safety-critical issue, it may be elevated to a mandatory AD.

Foreign airworthiness authority findings: If a foreign aviation authority (like EASA in Europe) issues an airworthiness directive for an aircraft type that operates in the US, the FAA typically issues a corresponding US AD.

Types of ADs

One-time compliance ADs: Require a specific action to be performed once. After compliance, the AD is considered resolved. Example: inspect a specific component and replace it if worn beyond limits.

Recurring ADs: Require repeated action at specified intervals — every 100 hours, every annual inspection, or at specific calendar intervals. These ADs never go away; they must be complied with continuously throughout the aircraft's life.

Emergency ADs: When the FAA identifies an immediate safety threat, it can issue an emergency AD with immediate or very short compliance deadlines. These are relatively rare but legally binding immediately upon issuance.

AD Notes in Type Certificate Data Sheets: Some ADs become part of the aircraft's ongoing airworthiness requirements and are referenced in the type certificate data sheet.

How to Find Which ADs Apply to Your Aircraft

Every aircraft has a specific set of applicable ADs based on its make, model, series, and the make and model of its engine, propeller, and avionics. Finding the complete list requires checking multiple sources:

FAA AD database: The FAA maintains a searchable AD database at rgl.faa.gov. You can search by aircraft make and model to find all applicable ADs.

FAA DRS (Dynamic Regulatory System): A more comprehensive database for researching ADs and regulatory requirements.

Aircraft type clubs: Type-specific owner organizations (Cessna Pilots Association, Piper Owner Society, etc.) often maintain curated AD lists for their specific aircraft type.

Your A&P mechanic: Any competent A&P familiar with your aircraft type will know the common recurring ADs for that make and model.

Aeradex Hangar: Aeradex's Hangar feature automatically pulls the applicable AD list for any aircraft by N-number and tracks compliance status, so you can see at a glance which ADs are current and which are coming due.

How to Verify Compliance

AD compliance must be documented in the aircraft's maintenance logbooks. For each applicable AD, you should be able to find a logbook entry showing:

• The AD number
• The date of compliance
• The aircraft total time at compliance
• The method of compliance (what was done)
• The name and certificate number of the person who performed the work

For recurring ADs, there should be entries showing each time the AD was complied with throughout the aircraft's history.

ADs During a Pre-Purchase Inspection

When evaluating a used aircraft, AD compliance verification is one of the most important parts of the pre-purchase inspection. An aircraft with unresolved ADs is not airworthy. The cost of coming into AD compliance on a neglected aircraft can be significant.

Common issues found during pre-purchase AD audits:

• ADs that were complied with but not documented in the logbook
• Recurring ADs that fell out of compliance
• ADs for components (engines, avionics) that weren't researched because the buyer only checked the airframe

Aeradex pre-purchase reports include AD compliance information based on FAA airworthiness data. Run a free report on any N-number at aeradex.com before making a purchase offer.