• David Botich

Do Experimental Aircraft need to comply with AD's and Airworthiness Limitations?

January, 2021

This question has come up in the past so I wanted to clarify this. Some people are under the impression that an aircraft operating under an Experimental Airworthiness Certificate is not required to comply with AD’s or Airworthiness Limitations. All of this is spelled out in the FAA Regulations. All aircraft operating within the US must comply with FAR Part 91.

91.1 Applicability.

(a) Except as provided in paragraphs (b), (c), (e), and (f) of this section and §§91.701 and 91.703, this part prescribes rules governing the operation of aircraft within the United States, including the waters within 3 nautical miles of the U.S. coast.

Part 91 is applicable to aircraft regardless as to what type of Airworthiness Certificate that aircraft carries. The only exceptions here are ultralight vehicles, small unmanned systems, operation outside of the US, etc.

91.403 General.

(a) The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39 of this chapter.

(b) No person may perform maintenance, preventive maintenance, or alterations on an aircraft other than as prescribed in this subpart and other applicable regulations, including part 43 of this chapter.

(c) No person may operate an aircraft for which a manufacturer's maintenance manual or instructions for continued airworthiness has been issued that contains an airworthiness limitations section unless the mandatory replacement times, inspection intervals, and related procedures specified in that section or alternative inspection intervals and related procedures set forth in an operations specification approved by the Administrator under part 121 or 135 of this chapter or in accordance with an inspection program approved under §91.409(e) have been complied with.

(d) A person must not alter an aircraft based on a supplemental type certificate unless the owner or operator of the aircraft is the holder of the supplemental type certificate, or has written permission from the holder.

Regarding AD’s

Refer to 91.403(a) above. AD’s are issued by the FAA and are mandatory for any product as specified within the AD. This includes the airframe, engine, propeller, instrument, equipment, etc. that is installed on any aircraft that is operating under US registration. That means that if it has an N number this will apply.

39.3 Definition of airworthiness directives

FAA' airworthiness directives are legally enforceable rules that apply to the following products: aircraft, aircraft engines, propellers, and appliances.

Regarding Airworthiness Limitations

Refer to 91.403(c) above. This is pretty clear as it states that the Airworthiness Limitations issued by the manufacturer must be complied with. IE: If you are operating a Bell OH58 helicopter that has an Experimental Exhibition AW Certificate you are still required to comply with all the original manufacturer's Airworthiness Limitations section that spells out the life limited components, such as main rotor blades, tail rotor blades, driveshafts, engine turbine wheels, etc.

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