Airworthiness Criteria: Special Class Airworthiness Criteria for the AgustaWestland Philadelphia Corporation Model AW609 Powered-Lift

<RULE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 21</CFR> <DEPDOC>[Docket No. FAA-2022-1726]</DEPDOC> <SUBJECT>Airworthiness Criteria: Special Class Airworthiness Criteria for the AgustaWestland Philadelphia Corporation Model AW609 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 AgustaWestland Philadelphia Corporation (AWPC) Model AW609 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 December 2, 2024. </EFFDATE> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Richard C Snyder, Certification Coordination Section, AIR-613, Policy and Standards Division, Aircraft Certification Service, 10101 Hillwood Parkway, Fort Worth, TX 76177; telephone and fax 817-222-4486; email <E T="03">richard.c.snyder@faa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Background</HD> The AWPC Model AW609 is a two-engine powered-lift with a maximum weight of 17,500 lbs., and a capacity of two crew and nine passengers. The aircraft has two “proprotors” instead of propellers or rotors. The AW609 design is a direct descendant of the Bell Helicopter Model BA609 certification project, which had design origins from the experimental Bell XV-15 aircraft. The FAA issued a notice of proposed airworthiness criteria for the AW609 powered-lift, which published in the <E T="04">Federal Register</E> on June 9, 2023 (88 FR 37805). After several changes of applicants, on February 15, 2012, AgustaWestland Tilt-Rotor Company, now AWPC, applied for a type certificate for the Model AW609. Under 14 CFR 21.17(c), an application for type certification is effective for three years, unless the FAA approves a longer period. Section 21.17(d) provides that, where a type certificate has not been issued within the time limit established under § 21.17(c), the applicant may file for an extension and update the designated applicable regulations in the type certification basis. Since the project was not certificated within the established time limit, the FAA approved a series of requests for extension by AWPC with the most recent request submitted on February 22, 2024. If the application extension is approved, the date of the updated type certification basis will change from March 31, 2021, to March 31, 2024. <HD SOURCE="HD1">Discussion</HD> Powered-lift are type certificated as special class aircraft because the FAA has not yet established powered-lift airworthiness standards as a separate part of subchapter C of 14 CFR. Under the procedures in § 21.17(b), the airworthiness requirements for special class aircraft are the portions of the requirements in 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 for type certification of the Model AW609 powered-lift under § 21.17(b). The powered-lift has characteristics of both a rotorcraft and an airplane. It is designed to function as a helicopter for takeoff and landing, and as an airplane cruising at higher speeds than a helicopter during the enroute portion of flight operations. Accordingly, the Model AW609 certification basis contains standards from parts 23, 25, and 29, as well as other airworthiness criteria specific for a powered-lift. This certification basis includes parts 23, 25, and 29 airworthiness standards. These are part 23 at amendment 23-62, part 25 at amendment 25-135 (except § 25.903(a) at amendment 25-140 and § 25.1517 at amendment 25-86), and part 29 at amendment 29-55 (except § 29.1353 at amendment 29-59). The certification basis incorporates by reference existing transport category airplane and rotorcraft standards, one normal category airplane standard, Category A rotorcraft standards, optional Category B rotorcraft standards, and criteria for operation under instrument flight rules. Flight into known icing conditions (FIKI) is not being sought with the current certification; however, FIKI is included in these airworthiness criteria for future certifications. The certification basis also includes new criteria unique to the powered-lift design, designated as tiltrotor (TR) criteria. Many of these TR criteria consist of modified part 25 or 29 standards. Some include criteria that combine existing parts 23, 25, and 29 standards, as the maximum weight of the Model AW609 exceeds the weight for normal category rotorcraft and most part 23 category airplanes, but its passenger seating is less than that of a transport category airplane or a transport category rotorcraft. The FAA also developed TR criteria because no existing standard captures the powered-lift's transitional flight modes (during flight, the powered-lift nacelle rotates the proprotor system from providing vertical lift to horizontal propulsion). The TR criteria also contain definitions specific for the powered-lift, such as flight modes, configurations, speeds, and terminology (“flaperon” instead of “aileron” or “flap;” “proprotor” instead of “rotor” or “propeller”). For example, while existing parts 25 and 29 standards for passenger emergency exits include a size classification (types I, II, III, IV) depending on the passenger seating capacity and other factors, the certification basis has a TR with criteria for the specific type of passenger emergency exit that is part of the design of the Model AW609. Another example involves fatigue evaluation. Part 25 contains requirements such as a limit of validity (LOV) on airframe fatigue for pressurized fuselages, which are not in part 29. Instead, fatigue evaluation in part 29 includes a composite structures fatigue rule, due to the more extreme fatigue environment of rotorcraft. For small airplanes, part 23, amendment 23-48, added a composite airframe evaluation requirement for bonded joints, which is included in agency compliance guidance for parts 25 and 29 but not required by a specific regulation (the safety requirement is complied with through other broad existing regulations in those parts). Since the Model AW609 has a pressurized fuselage, the FAA developed TR criteria to include the LOV requirement. The certification basis incorporates by reference the part 29 composite rotorcraft structures fatigue rule, TR criteria to include the composite bonding requirements from part 23, as well as TR criteria to include fatigue requirements for elastomeric primary structural elements. The new requirements specific to the AWPC Model AW609 in the proposed airworthiness criteria used a “TR.xxxx” section-numbering scheme. <HD SOURCE="HD1">Summary of Changes From the Proposed Airworthiness Criteria</HD> Based on comments received, these final airworthiness criteria reflect the following changes, in addition to others as explained in more detail in the Discussion of Comments section: • Added § 29.1547 to the final airworthiness criteria for the case where a magnetic compass is installed. • Revised these final airworthiness criteria to provide clarification on future certification for FIKI conditions. • Clarified statements about TR.45 applicability. • Revised proposed TR.575 to account for the unique nature and operating environment of elastomeric principle structural elements (PSEs). • Updated § 25.775 to clarify that the reference to § 25.335(a) is replaced with TR.335(a) for the purposes of these airworthiness criteria. • Did not include § 25.875 and updated TR.875 in these final airworthiness criteria to prevent confusion between the terms propeller and proprotor, thereby combining proposed TR.875 and § 25.875, which call out requirements for buffeting, proprotor (propeller), and other rotating components. Accordingly, TR.875 in these final airworthiness criteria addresses both proposed TR.875 and § 25.875. • Revised the incorporation by reference of § 29.1521 to reflect that the reference to § 29.1509(c) is replaced with TR.1509(c) since § 29.1509 is not part of the type certification basis for the Model AW609. • Specified the amendment level for § 25.1517 to be 25-86. • Revised these airworthiness criteria to remove § 25.1353 and include § 29.1353 at amendment 29-59 for electrical wiring protection due to recent amendments to part 29. <HD SOURCE="HD1">Addition of Position Light TRs</HD> After the FAA issued the notice of proposed airworthiness criteria for public comment, AWPC presented a forward left and right position light design that would not meet the prescriptive regulatory requirements defined under §§ 29.1385-29.1395. In general terms, the existing requirements define the use of a single left and a single right forward-looking position light. Due to the AW609 configuration, AWPC proposed using multiple light sources for each forward position light providing lighting at a level comparable to the part 29 lighting requirements. The FAA developed TR.1385, TR.1387, TR.1389, TR.1391, TR.1393, and TR.1395 to establish the same level of safety to §§ 29.1385, 29.1387, 29.1389, 29.1391, 29.1393, and § 29.1395 to address the non-traditional configuration of the AW609 powered-lift's position lights. These TRs modified the language in certain part 29 sections to allow for a group of forward position lights to be installed on each side of the aircraft. <HD SOURCE="HD1">Discussion of Comments</HD> The ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 33k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━