What Are Airworthiness Directives?
Dr. Mary Ann O’Grady
The Federal Aviation Administration (FAA) issues legally enforceable Airworthiness Directives or ADs for the purpose of correcting an unsafe condition in an aircraft, aircraft engine, propeller, or appliance under 14 CFR Part 39. The FAA Aircraft Certification Service maintains 12 Aircraft Certification Offices (ACOs) within four Directorates, and each one is responsible for the continued operational safety of the products over which it holds jurisdiction. This directorate responsibility is assigned by the type of product: transport category airplanes, small airplanes, rotorcraft, or engines and propellers. The Aviation Safety Engineers (ASEs) employed by the Directorate monitor the assigned products to identify unsafe conditions, and the necessity to generate airworthiness directives. These ASEs are also responsible for monitoring products that are manufactured in other countries but are approved for use in the United States as well as initiating airworthiness directives for those products as deemed necessary. The functions of the four Directorates can be details as follows: to draft, coordinate, and issue airworthiness directives based upon the information that is provided by an ACO or Directorate Standards Staff.
The responsibility of the owner of a Type Certificate that has been issued an AD involves:
- Notifying the FAA when they are made aware of any failure malfunction, or defect in any product, part, process, or article manufactured by them.
- Developing appropriate design changes to correct any unsafe condition.
- Incorporating the correction (corrective action) in the future generation of the product that will ensure that the product remains in a safe operating condition.
Aircraft owners as well as operators are responsible for ensuring that they are in compliance with the requirements of all airworthiness directives that apply to their aircraft. Anyone who continues to operate a product that is not in compliance with an applicable AD is in violation of 14 CFR 39.7. In order to locate all applicable ADs, an online search must be conducted for the product, such as for the aircraft, engine(s), propeller, or any other installed appliance. If multiple series are discovered under the aircraft or engine model, it then becomes necessary to also search for ADs that are applicable to the model as well as to the specific series of that model. No person may operate a product to which an AD has been issued except in accordance with the requirements of the AD, and the owner or operator of an aircraft must continue to remain in compliance with all ADs within the compliance time that relates to the effective date of the AD which determines when the actions are required.
Airworthiness directives are constructed in two parts: the preamble and the rule, where the former section provides the basis and the purpose of the AD while the latter section provides the regulatory requirements for correcting the unsafe condition(s). Typically the ADs will include: the description of the unsafe condition; the product to which the AD applies; the required corrective action, operating limitations or both; the AD effective date; a compliance time; the source for additional information; and information regarding alternative methods of compliance with the requirements of the AD. ADs provide a three-part number designator which can be demystified as follows: the first part is the calendar year of issuance; the second part consists of the biweekly period of the year when the number is assigned; and the third part is issued sequentially within each biweekly period. It is important to note that not all ADs necessitate a corrective action; some ADs just include limitations, but each AD is intended to resolve an unsafe condition.
The Federal Register is the official daily publication of the United States government which generates the printed or hard copy method of providing information to the public regarding laws that have been enacted or will be enacted. Electronic versions of the airworthiness directives are available from the Federal Register and from the FAA Regulatory and Guidance Library (RGL). The RGL contains all of ADs which can be searched under the manufacturer, model or AD number itself. Electronic copies of the ADs can be downloaded from the RGL to the computer of the owner or operator, and subscription services are also available via email from the RGL home page. Once a subscription has been activated, any AD that pertains to aircraft and engine makes and models that have been selected, will be emailed as attachments within minutes of the document being posted. The FAA provides the public an opportunity to comment on the notices of proposed rulemaking as well as on final rule ADS that are published without prior notice. They are all published in the Federal Register and include information regarding how to submit comments. The FAA does not request comments regarding Emergency ADs at the time of their issuance although the FAA does request comments when they are published as a final rule AD in the Federal Register.
The standard airworthiness directive process for the three types of ADs (Notice of Proposed Rulemaking or NPRM, which is followed by a Final Rule, Final Rule, Request for Comments and Emergency ADs) adheres to the following procedure: once an unsafe condition is identified, a proposed solution is published as an NPRM, which then solicits public comment on the proposed action. After the comment period concludes, the final rule is generated while considering all substantive comments received, with the rule perhaps being changed as warranted by those comments. The preamble to the final rule AD provides response to the substantive comments or states that there were no comments received. In cases where the critical nature of an unsafe condition warrants the immediate adoption of a rule without prior notice and/or the solicitation of comments (typically in less than 60 days), a finding of impracticability becomes justified for the terminating action which allows it to be issued as an immediately adopted rule which is then published in the Federal Register with a request for comments. The Final Rule AD may be changed later if substantive comments are received. When an Emergency AD is issued, it requires immediate action by the owner or operator since its intent is to rapidly correct an urgent safety of flight situation. An AD is considered to be no longer in effect when it has been superseded by a new AD which states that the previous AD is no longer in effect and that there are no compliance requirements for an AD that has been superseded.
Different approaches or Alternative Methods of Compliance (AMOC) that are not specified in an original airworthiness directive can, with FAA approval, be used to correct an unsafe condition on an aircraft or aircraft product. Although the proposed alternative may not have been known at the time the AD was originally issued, it could be acceptable to accomplish the intent of the original AD. A compliance time that differs from the requirements of the original AD can also be approved if the revised time period provides an acceptable level of safety that equals or exceeds the requirements posted in the original AD. Provisions for an AMOC are desirable from the owner’s or operator’s point of view because it can eliminate the necessity of constant AD revisions when acceptable methods are developed for AD compliance. If an AD does not contain any provision(s) for approving an AMOC, the AD must undergo revisions before compliance can be accomplished by any method other than what is stated in the original AD. Each AD states which office within the FAA Aircraft Certification Service that is responsible for that particular AD. An AMOC can be approved by the manager of the office that is responsible for that specific AD including different compliance times for the requirements of a specific AD. One FAA Aircraft Certification Office will have responsibility for AMOC approvals for products manufactured within the United States while a product manufactured outside of the United States will be under the jurisdiction of a Standards Staff branch office of one of the four FAA Aircraft Certification Directorates.
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