At the simplest terms an Airworthiness Directive is:
"A regulatory notice sent out by the FAA to the registered owner of an aircraft informing the owner of a condition that prevents the aircraft from continuing to meet its conditions for airworthiness. Airworthiness Directives (AD notes) are to be complied with within the required time limit, and the fact of compliance, the date of compliance, and the method of compliance are recorded in the aircraft’s maintenance records."
Generally there are regular ADs and emergency ADs. Regular ADs usually have a time period (flight hours or calendar time) that it must be complied with and can be one-time compliance or recurring (usually an inspection). Emergency ADs bypass the normal rulemaking process and may need to be complied with before the aircraft can fly again, or in the case of avionics you could be restricted to VFR flying till its corrected.
Most of the questions we get are concerning ADs on a certain aircraft or part. This information can be found/searched for on the FAA's AD page. You'll want to remember when using this page that the AD may be under a different name. For example when looking for C172 ADs, you'll have to search for Textron instead of Cessna, as a search of the term Cessna doesn't bring up anything.
ADs are issued for airframe, powerplant, and appliances. Its a good idea to have a list of appliances (mags, starter, avionics, etc.) that are on your aircraft (manufacturer, serial number, time in service) so it makes the AD search and compliance much easier. Putting together AD compliance list that states what ADs have been complied with and which ones are coming due will make your life easier and should make future annuals faster and cheaper. It also will make your life easier when you go to fly and try to determine whether the aircraft is airworthy.
Please feel free to make comments below with more information of ADs that you think that other pilots/owners may find useful or questions you may have on the topic.
Question: I had some recalls on my car, but accomplishing the inspection/repair and such cost me nothing, other than time, a couple hours at the dealership. So for aviation, Why is the aircraft owner responsible for the cost of returning the aircraft to airworthy, and not the manufacturer ?
Why is the aircraft owner responsible for the cost of returning the aircraft to airworthy, and not the manufacturer ?
Because Federal law does not require it the way it does for automobiles. Beyond that, you'd have to ask your Congressional Representatives.
And that said, at the risk of getting political, it might also have something to do with the fact that hundreds of million of voters own cars but only tens of thousands of voters own airplanes.
May an owner/pilot legally determine the applicability of an airworthiness directive or must this be done by a certified mechanic. Example: I received and AD for a prop governor with a list of affected part numbers. I can verify in the prop log this part number is not installed on my aircraft. May I legally make a logbook entry stating the AD does not apply?
Since the owner is responsible under 91.403 to maintain their aircraft in compliance with AD's, they are also allowed to determine the applicability of an AD to their type. As always, READ CAREFULLY, as AD's can have many fine print traps. Owners are legal to do a maintenance record entry in accordance with 43.9 without being an A&P because no work is being performed on the aircraft. It will, however, be advisable for a non A&P owner's IA to double check the AD status at annual time.