In accordance with part 91 the owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with AD's. The owners and operators are responsibility for complying with airworthiness directives (AD) and recording AD compliance in the appropriate maintenance records. However, during aircraft inspections FAA Airframe and Powerplant (A&P) mechanic share a dual responsible in complying with ADs if the product is manufactured to FAA rules under part 21. The FAA issues AD's when an unsafe condition is found to exist in a product (aircraft, aircraft engine, propeller, or appliance) of a particular type design. AD's are used by the FAA to notify aircraft owners and operators of unsafe conditions and to require their correction. AD's prescribe the conditions and limitations, including inspection, repair, or alteration under which the product may continue to be operated. AD's may be issued which apply to aircraft engines, propellers, or appliances installed on multiple makes or models of aircraft. When the product can be identified as being installed on a specific make or model aircraft, the AD is distributed by first class mail to the registered owners of those aircraft. APPLICABILITY OF AD's Each AD contains an applicability statement specifying the product (aircraft, aircraft engine, propeller, or appliance) to which it applies. Some aircraft owners and operators mistakenly assume that AD's do not apply to aircraft with other than standard airworthiness certificates, i.e., special airworthiness certificates in the restricted, limited, or experimental category. Unless specifically stated, AD's apply to the make and model set forth in the applicability statement regardless of the classification or category of the airworthiness certificate issued for the aircraft. Type certificate and airworthiness certification information are used to identify the product affected. Limitations may be placed on applicability by specifying the serial number or number series to which the AD is applicable. When there is no reference to serial numbers, all serial numbers are affected. EXPERIMENTAL AIRCRAFT As stated above the AD will apply regardless of the classification or category of the airworthiness certificate issued for the aircraft. What this means is if you own an experimental aircraft that has a product installed which an AD applies you MUST comply with the AD. Some owner are misinformed that by taking the data plate off an engine or propeller will do away with the AD, but it will not. This is where the experimental limitations which are part of the experimental airworthiness certificate play into how the aircraft is maintained. Do NOT assume ADs to not apply because you are it is an experimental aircraft they do apply. Every AD applies to each product identified in the applicability statement, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of the AD. For products that have been modified, altered, or repaired so that performance of the requirements of the AD is affected, the owner/operator must use the authority provided in the alternative methods of compliance provision of the AD to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or, different actions necessary to address the unsafe condition described in the AD. In no case, does the presence of any alteration, modification, or repair remove any product from the applicability of this AD. Performance of the requirements of the AD is “affected” if an operator is unable to perform those requirements in the manner described in the AD. In short, either the requirements of the AD can be performed as specified in the AD and the specified results can be achieved, or they cannot. The belief that AD compliance is only required at the time of a required inspection, e.g., at a 100-hour or annual inspection is not correct. The required compliance time is specified in each AD, and no person may operate the affected product after expiration of that stated compliance time. NOTE: When a direct relationship between airworthiness and calendar time is identified, compliance time may be expressed as a calendar date. For example, if the compliance time is specified as "within 12 months after the effective date of this AD...." with an effective date of July 15, 1995, the deadline for compliance is July 15, 1996. This is a part 91.417 rule. MAINTENANCE PERSONNEL The person accomplishing the AD is required by part 43 section § 43.9 to record AD compliance. The entry must include those items specified in § 43.9 (a) (1) through (a) (4). The owner or operator is required by § 91.405 to ensure that maintenance personnel make appropriate entries and, by § 91.417, to maintain those records. Owners and operators should note that there is a difference between the records required to be kept by the owner under § 91.417 and those § 43.9 requires maintenance personnel to make. In either case, the owner or operator is responsible for maintaining proper records. REGISTERED OWNER OR OPERATOR of an aircraft is responsible for compliance with AD's applicable to the airframe, engine, propeller, appliances, and parts and components thereof for all aircraft it owns or operates. MAINTENANCE PERSONNEL are responsible for determining that all applicable airworthiness requirements are met when they accomplish an inspection in accordance with part 43 even on experimental aircraft.