An airworthiness directive commonly known as an AD is a mandatory instruction that must be carried out when it is applicable to your aircraft within a given time frame.
The airworthiness directive for example might be repetitive in nature, it might have an option to terminate the requirement by performing a modification or it might be a one-off task. One query you might have to address is the embodiment or accomplishment date for a given AD and this can be very important, especially when considering any instructions for continued airworthiness
(ICA).