Airworthiness Criteria: Special Class Airworthiness Criteria for the Archer Aviation, Inc. Model M001 Powered-Lift

<RULE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 21</CFR> <DEPDOC>[Docket No. FAA-2022-1548]</DEPDOC> <SUBJECT>Airworthiness Criteria: Special Class Airworthiness Criteria for the Archer Aviation, Inc. Model M001 Powered-Lift</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), DOT. <HD SOURCE="HED">ACTION:</HD> Issuance of final airworthiness criteria. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The FAA announces the special class airworthiness criteria for the Archer Aviation, Inc. (Archer) Model M001 powered-lift. This document sets forth the airworthiness criteria the FAA finds to be appropriate and applicable for the powered-lift design. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> These airworthiness criteria are effective June 24, 2024. </EFFDATE> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> James Clary, Emerging Technology Coordination Section, AIR-611, Policy and Standards Division, Aircraft Certification Service, Federal Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX 76177; telephone 817-222-5138; email <E T="03">james.clary@faa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Background</HD> On March 30, 2022, Archer applied for a type certificate for the Model M001 powered-lift. The Archer Model M001 powered-lift has a maximum gross takeoff weight of 6,500 lbs. and is capable of carrying a pilot and four passengers. The aircraft has a high-wing and V-tail  <SU>1</SU> <FTREF/> configuration with fixed tricycle landing gear. The aircraft uses 12 electric engines powered by onboard batteries for propulsion instead of conventional air and fuel combustion. Six engines with five-bladed variable-pitch propellers are mounted on the forward edge of the main wing, three to each side, which are capable of tilting to provide both vertical and forward thrust. The other six electric engines drive two-bladed fixed-pitch propellers and are mounted on the aft edge of the main wing, three to each side; they are fixed in place to provide only vertical thrust. The aft-mounted engines operate only during thrust-borne or semi-thrust- borne flight; in wing-borne forward flight, these engines are switched off and the propellers are faired in line with the aircraft fuselage. The aircraft structure and propellers are constructed of composite materials. The Archer Model M001 powered-lift is intended to be used for Title 14, Code of Federal Regulations (14 CFR) parts 91 and 135 operations, with a single pilot onboard, under visual flight rules (VFR). <FTNT> <SU>1</SU>  A V-Tail aircraft design incorporates two slanted tail surfaces instead of the horizontal and vertical fins of a conventional aircraft empennage. The two fixed tail surfaces of a V-Tail act as both horizontal and vertical stabilizers and each has a moveable flight-control surface referred to as a ruddervator. </FTNT> The FAA issued a notice of proposed airworthiness criteria for the Model M001 powered-lift, which published in the <E T="04">Federal Register</E> on December 20, 2022 (87 FR 77749). <HD SOURCE="HD1">Discussion</HD> Because the FAA has not yet established powered-lift airworthiness standards in 14 CFR, the FAA type certificates powered-lift as special class aircraft. Under the procedures in § 21.17(b), the airworthiness requirements for special class aircraft, including the engines and propellers installed thereon, are the portions of the requirements in 14 CFR parts 23, 25, 27, 29, 31, 33, and 35 found by the FAA to be appropriate and applicable to the specific type design and any other airworthiness criteria found by the FAA to provide an equivalent level of safety to the existing standards. These final airworthiness criteria announce the applicable regulations and other airworthiness criteria developed, under § 21.17(b), for type certification of the Model M001 powered-lift. The Model M001 powered-lift has characteristics of both a rotorcraft and an airplane. It is designed to function as a rotorcraft for takeoff and landing and as an airplane cruising at speeds higher than a rotorcraft during the enroute portion of flight operations. The electric engines on the Model M001 powered-lift will use electrical power instead of air and fuel combustion to propel the aircraft through six five-bladed composite variable-pitch propellers for all phases of flight, and six two-bladed fixed-pitch propellers for vertical and transitional flight modes only. Accordingly, the Archer Model M001 powered-lift proposed airworthiness criteria contained standards from parts 23, 33, and 35 as well as other proposed airworthiness criteria specific for a powered-lift and the electric engines and propellers installed thereon. For the existing regulations that were included without modification, the proposed airworthiness criteria included all amendments to the existing parts 23, 33, and 35 airworthiness standards in effect as of the application date of March 30, 2022. These are part 23, amendment 23-64, part 33, amendment 33-34, and part 35, amendment 35-10. The Archer Model M001 powered-lift proposed airworthiness criteria also included new performance-based airworthiness criteria. The FAA developed these criteria because no existing standard captured the powered-lift's various flight modes and electric engines and some unique characteristics of their propellers. The new requirements specific to the Archer Model M001 in the proposed airworthiness criteria used an “AM1.xxxx” section-numbering scheme. Because many of the proposed airworthiness criteria are performance-based, like the regulations found in part 23, the FAA has proposed to adopt § 23.2010 by reference, which would require that the means of compliance used to comply with the airworthiness criteria be accepted by the Administrator. Because no powered-lift consensus standards are currently accepted by the Administrator, the means of compliance will be accepted through the issue paper process. <SU>2</SU> <FTREF/> <FTNT> <SU>2</SU>  See Order 8110.112A, <E T="03">Standardized Procedures for Usage of Issue Papers and Development of Equivalent Levels of Safety Memorandums.</E> </FTNT> <HD SOURCE="HD1">Summary of Changes From the Proposed Airworthiness Criteria</HD> These final airworthiness criteria reflect the following changes, in addition to others as explained in more detail under Discussion of Comments: The FAA made changes to the aircraft performance section to incorporate an optional, “increased performance” approval, which requires greater aircraft performance capabilities beyond that of the baseline “essential performance” approval. The expectations for aircraft performance at both levels are clearly defined at the requirement level. Requirements to address various scenarios involving failures that can lead to loss of thrust were clarified and consolidated into a consistent terminology across all airworthiness criteria. Expectations were added for the aircraft to be capable of a controlled emergency landing following any condition where the aircraft can no longer provide the commanded power or thrust required for continued safe flight and landing (CSFL). The proposed requirement to incorporate a bird strike deterrent system was not adopted in these final airworthiness criteria, nor were other requirements not applicable to the Model M001, such as requirements for operations on water, approval for aerobatic flight, and others, as discussed in further detail under Discussion of Comments. The FAA modified and developed revised aeroelasticity criteria to more directly address concerns expressed by commenters related to “whirl flutter” and aeromechanical stability. The FAA revised requirements in response to numerous comments requesting clarification or recommending changes to address safety gaps in the proposed criteria, particularly in the areas of aircraft handling and control, structural airframe loads and durability, flight controls, protection of occupants, and protection of systems from high-intensity radiated fields (HIRF) and lightning. The FAA updated requirements for electric engines in response to requests for improved clarity on applicability and relationship to the airframe requirements. The FAA also updated definitions for “controlled emergency landing,” “CSFL,” and “sources of lift” and added a definition for “local events.” Lastly, the FAA clarified that, should Archer apply to amend the type certificate to include another model powered-lift, these airworthiness criteria would apply to that model also, provided the criteria remain appropriate to the changed aircraft in accordance with part 21, subpart D. This change was necessary so that each future change to the aircraft will not necessarily require an application for a new type certificate. <HD SOURCE="HD1">Discussion of Comments</HD> The FAA received responses from 22 commenters. The majority of commenters were government agencies, private companies, and organizations as follows: Agência Nacional de Aviação Civil (ANAC); Airbus; Air Line Pilots Association (ALPA); Alaka'i Technologies Corporation (Alaka'i); Aerospace, Security and Defence Industries Association of Europe (ASD-Europe); Association for Uncrewed Vehicle Systems International (AUVSI); United Kingdom Civil Aviation Authority (UKCAA); European Union Aviation Safety Agency (EASA); General Aviation Manufacturers Association (GAMA); IPR; Japan Civil Aviation Bureau (JCAB); Leonardo Helicopters (Leonardo); Lilium eAircraft GmbH (Lilium); Odys Aviation (Odys); Overair Inc. (Overair); Rolls-Royce Deutschland Ltd & Co KG (Rolls-Royce); SkyDrive, Inc. (SkyDrive); Transport Canada Civil Aviation (TCCA); Vertical Aerospace; and Volocopter GmbH (Volocopter). The FAA received comments from one individual commenter and from one anon ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 243k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━