Airworthiness Directives (Ads) are substantive regulations issued by the Federal Aviation Administration (FAA) in accordance with Title 14 of the Code of Federal Regulations (14 CFR) part 39. Ads are issued when (1) an unsafe condition exists in the product (i.e., aircraft, aircraft engine, propeller, or appliance), and (2) the condition is likely to exist or develop in other products of the same type design. Once an AD is issued, no person may operate a product to which the AD applies except in accordance with the requirements of that AD. This manual provides policy and guidance for the drafting, issuance, and distribution of Ads. It is intended to explain the laws that apply to Ads, procedures for writing an AD, and policies on key AD-related issues. About the Author: The Federal Aviation Administration (FAA) is an agency of the United States Department of Transportation with authority to regulate and oversee all aspects of civil aviation in the U.S. (National Airworthiness Authority). The Federal Aviation Act of 1958 created the group under the name "Federal Aviation Agency", and adopted its current name in 1967 when it became a part of the United States Department of Transportation. The Federal Aviation Administration's major roles include: Regulating U.S. commercial space transportation. Regulating air navigation facilities' geometry and Flight inspection standards. Encouraging and developing civil aeronautics, including new aviation technology. Issuing, suspending, or revoking pilot certificates. Regulating civil aviation to promote safety, especially through local offices called Flight Standards District Offices. Developing and operating a system of air traffic control and navigation for both civil and military aircraft. Researching and developing the National Airspace System and civil aeronautics. Developing and carrying out programs to control aircraft noise and other environmental effects of civil aviation.