What is an airworthiness directive (AD)?
Updated · Wingman AeroCare, KFNL
Short answer: An airworthiness directive (AD) is a legally enforceable rule the FAA issues under 14 CFR Part 39 when it finds an unsafe condition in an aircraft, engine, propeller, or appliance that is likely to exist in other products of the same design. If an AD applies to your aircraft, you may not operate it unless the AD's requirements are met (14 CFR 39.7). Compliance is mandatory for every owner, including private Part 91 operators.
Why does the FAA issue ADs?
Under 14 CFR 39.5, the FAA issues an AD when two things are true: an unsafe condition exists in a product, and that condition is likely to exist or develop in other products of the same type design. Typical triggers include cracked parts found in service, accident or incident investigations, and problems reported by manufacturers.
An AD tells you what to do and when. Under 14 CFR 39.11, that can mean an inspection, a part replacement, a modification, a change to operating limitations, or a combination.
What kinds of ADs are there?
| Type | How it works |
|---|---|
| Standard AD (NPRM, then final rule) | The FAA proposes the AD, takes public comments, then publishes a final rule with an effective date. |
| Final rule, request for comments | Issued without a prior proposal when the risk is urgent, but comments are still accepted afterward. |
| Emergency AD | Sent directly to known owners and operators when immediate action is needed. It is effective for each recipient on receipt. |
ADs are numbered by year, biweekly period, and sequence, for example 2024-05-12. Revised ADs carry the same base number with a revision suffix, or are superseded by a new AD that replaces the old one.
One-time vs. recurring ADs
- One-time ADs are complied with once (for example, replacing a part with an improved design). After that, the AD stays on your compliance list as "complied with."
- Recurring ADs require repeat action at an hour or calendar interval, such as an inspection every 100 hours or every 12 months. These are the ones that get missed.
Many ADs also offer a "terminating action": a permanent fix that ends the recurring inspections.
Who is responsible for AD compliance?
The owner or operator is primarily responsible for maintaining the aircraft in an airworthy condition, including compliance with Part 39 (14 CFR 91.403(a)). Your mechanic performs and records the work, but the legal obligation is yours.
At every annual inspection, the inspector must determine whether the aircraft meets all applicable airworthiness requirements (14 CFR 43.15(a)(1)), and that includes ADs. An aircraft with an overdue AD cannot be signed off as airworthy.
How is AD compliance recorded?
Under 14 CFR 91.417(a)(2)(v), the owner must keep a record of the current status of applicable ADs, including:
- The AD number and revision date
- The method of compliance
- For recurring ADs, the time and date when the next action is due
These records transfer with the aircraft when it is sold (14 CFR 91.417(b)(2) and 91.419). A clean, current AD status list is one of the first things a buyer or inspector should ask for.
Can I get relief from an AD?
Two common paths:
- Alternative method of compliance (AMOC). Under 14 CFR 39.19, you can request FAA approval of a different way to meet the AD's intent. You must have the AMOC approved before relying on it.
- Special flight permit. Under 14 CFR 39.23, you can usually get a ferry permit to fly an aircraft to a place where the AD work can be done, unless the AD itself prohibits it.
Note that a manufacturer's service bulletin is not the same as an AD. Service bulletins are generally not mandatory for Part 91 operators unless an AD, an airworthiness limitation, or another rule makes them so. They are often still smart to follow.
How Wingman handles it
Wingman AeroCare performs AD and service bulletin compliance in-house for piston singles and twins at Northern Colorado Regional Airport (KFNL), and every annual includes a review of the ADs that apply to your airframe, engine, propeller, and appliances. Any AD work we find due shows up on your online estimate as an Airworthy item, with photos, so you see exactly what is required and why. Members of our Managed Maintenance Program get AD and SB tracking to the tail number, so recurring items do not sneak up on you. See AD compliance services or contact us.