Special Conditions: Skyryse, Robinson Helicopter Company Model R66 Helicopter; Interaction of Systems and Structures

<RULE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 27</CFR> <DEPDOC>[Docket No. FAA-2024-0875; Special Conditions No. 27-058-SC]</DEPDOC> <SUBJECT>Special Conditions: Skyryse, Robinson Helicopter Company Model R66 Helicopter; Interaction of Systems and Structures</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), DOT. <HD SOURCE="HED">ACTION:</HD> Final special conditions. <SUM> <HD SOURCE="HED">SUMMARY:</HD> These special conditions are issued for the Robinson Helicopter Company (Robinson) Model R66 helicopter. This helicopter, as modified by Skyryse, will have a novel or unusual design feature when compared to the state of technology envisioned in the airworthiness standards for normal category helicopters. This design feature is a novel control input and fly-by-wire (FBW) system. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for this design feature. These special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Effective December 13, 2024. </EFFDATE> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Daniel Moore, Airframe Section, AIR-622, Technical Policy Branch, Policy and Standards Division, Aircraft Certification Service, Federal Aviation Administration, 901 Locust, Kansas City, MO 64106; telephone (303) 342-1066; email <E T="03">Daniel.E.Moore@faa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Background</HD> On April 10, 2023, Skyryse applied for a supplemental type certificate for removal of the mechanical control system and installation of a computer controlled flight control system in the Model R66 helicopter. The Robinson Model R66 helicopter, currently approved under Type Certificate No. R00015LA, is a single engine normal category rotorcraft. The maximum take-off weight is 2,700 pounds, with a maximum seating capacity of five passengers. <HD SOURCE="HD1">Type Certification Basis</HD> Under the provisions of 14 CFR 21.101, Skyryse must show that the Robinson Model R66 helicopter, as changed, continues to meet the applicable provisions of the regulations listed in Type Certificate No. R00015LA or the applicable regulations in effect on the date of application for the change, except for earlier amendments as agreed upon by the FAA. If the Administrator finds that the applicable airworthiness regulations do not contain adequate or appropriate safety standards for the Robinson Model R66 helicopter because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16. Special conditions are initially applicable to the model for which they are issued. Should the applicant apply for a supplemental type certificate to modify any other model included on the same type certificate to incorporate the same novel or unusual design feature, these special conditions would also apply to the other model under § 21.101. In addition to the applicable airworthiness regulations and special conditions, the Robinson Model R66 helicopter must comply with the fuel-vent and exhaust-emission requirements of 14 CFR part 34, and the noise-certification requirements of 14 CFR part 36. The FAA issues special conditions, as defined in 14 CFR 11.19, in accordance with § 11.38, and they become part of the type certification basis under § 21.101. <HD SOURCE="HD1">Novel or Unusual Design Feature</HD> The Robinson Model R66 helicopter will incorporate the following novel or unusual design feature: Novel control input and FBW system. <HD SOURCE="HD1">Discussion</HD> Skyryse has proposed to install an FBW flight control system (FCS) intended to replace the current hydraulicly boosted mechanical primary FCS, on a Robinson Model R66 helicopter. FBW systems are new to part 27 rotorcraft and as such, the rotorcraft FCS will now contain control functions that affect the static strength of rotorcraft structure. These special conditions would give the applicant an option to offset the structural factor of safety based on the probability of system failure. These special conditions apply to systems that can induce loads on the airframe or change the response of the rotorcraft to maneuvers or to control inputs, as a result of failure. Some potential examples include part 27 rotorcraft equipped with FBW or fly-by-light FCSs, autopilots, stability augmentation systems, load alleviation systems, flutter control systems, fuel management systems, and other systems that either directly or as a result of failure or malfunction affect structural performance. The FAA has issued special conditions for the interaction of systems and structures to other aircraft in the past (parts 23, 25, and 29). Active flight control systems are capable of providing automatic responses to inputs from sources other than the pilots. These automatic systems may become inoperative or may operate in a degraded mode, which could impact the loads envelope and rotorcraft static strength. Therefore, it is necessary to determine the structural factors of safety and operating margins such that the joint probability of structural failures due to application of loads during system malfunctions is not greater than that found in rotorcraft equipped with earlier technology control systems. To achieve this objective, it is necessary to define the failure conditions with their associated frequency of occurrence in order to determine the structural factors of safety and operating margins that will ensure an acceptable level of safety. The special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards. <HD SOURCE="HD1">Discussion of Comments</HD> The FAA issued Notice of Proposed Special Conditions No. 27-24-01-SC for the Robinson Model R66 helicopter, as modified by Skyryse, which was published in the <E T="04">Federal Register</E> on August 28, 2024 (89 FR 68833). No comments were received, and the special conditions are adopted as proposed. <HD SOURCE="HD1">Applicability</HD> As discussed above, these special conditions are applicable to the Robinson R66 helicopter. Should Skyryse apply at a later date for a supplemental type certificate to modify any other model included on Type Certificate No. R00015LA to incorporate the same novel or unusual design feature, these special conditions would apply to that model as well. Under standard practice, the effective date of final special conditions would be 30 days after the date of publication in the <E T="04">Federal Register</E> . However, as the certification date for the Robinson R66 helicopter, as modified by Skyryse, is imminent, the FAA finds that good cause exists to make these special conditions effective upon publication. <HD SOURCE="HD1">Conclusion</HD> This action affects only a certain novel or unusual design feature on one model of helicopter. It is not a rule of general applicability and affects only the applicant who applied to the FAA for approval of these features on the helicopter. <HD SOURCE="HD1">List of Subjects in 14 CFR Part 27</HD> Aircraft, Aviation safety, Reporting and recordkeeping requirements. <HD SOURCE="HD1">Authority Citation</HD> The authority citation for these special conditions is as follows: <HD SOURCE="HED">Authority:</HD> 49 U.S.C. 106(f), 106(g), 40113, 44701, 44702, 44704. <HD SOURCE="HD1">The Special Conditions</HD> Accordingly, pursuant to the authority delegated to me by the Administrator, the following special conditions are issued as part of the type certification basis for the Robinson R66 helicopter, as modified by Skyryse. <HD SOURCE="HD2">Interaction of Systems and Structures</HD> For rotorcraft equipped with systems that affect structural performance, either directly or as a result of a failure or malfunction, the influence of these systems and their failure conditions must be taken into account when showing compliance with the requirements of subparts C and D of part 27 of title 14 of the Code of Federal Regulations (14 CFR). The following criteria must be used for showing compliance with these special conditions: (a) The criteria defined herein only address the direct structural consequences of the system responses and performance. They cannot be considered in isolation but should be included in the overall safety evaluation of the rotorcraft. These criteria may, in some instances, duplicate standards already established for this evaluation. These criteria are only applicable to structures whose failure could prevent continued safe flight and landing. Specific criteria that define acceptable limits on handling characteristics or stability requirements, when operating in the system degraded or inoperative mode, are not provided in these special conditions. (b) Depending upon the specific characteristics of the rotorcraft, additional studies may be required that go beyond the criteria provided in these special conditions in order to demonstrate the capability of the rotorcraft to meet other realistic conditions such as alternative gust or maneuver descriptions for a rotorcraft equipped with a load alleviation system. (c) The following definitions are applicable to these special conditions. (1) <E T="03">Structural performance:</E> Capability of the rotorcraft to meet the structural requirements of 14 CFR part 27. (2) <E T="03">Flight limitations:</E> Limitations that can be applied to the rotorcraft flight conditions following an in-flight occurrence and that are included in the flight ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 20k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━