Special Conditions: Sikorsky Model S-61A, S-61L, and S-61N (Including Those Modified by Supplemental Type Certificate (STC) No. SH640NE) Helicopters; Overload Protection Device in a Hoist

<RULE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 29</CFR> <DEPDOC>[Docket No. FAA-2024-2383; Special Conditions No. 29-059-SC]</DEPDOC> <SUBJECT>Special Conditions: Sikorsky Model S-61A, S-61L, and S-61N (Including Those Modified by Supplemental Type Certificate (STC) No. SH640NE) Helicopters; Overload Protection Device in a Hoist</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 Sikorsky Aircraft Corporation and Sikorsky Aircraft (Sikorsky) Model S-61A, S-61L, and S-61N helicopters. These helicopters, as modified by Carson Helicopters Inc. (Carson), will have a novel or unusual design feature when compared to the state of technology envisioned in the airworthiness standards for transport category rotorcraft. This design feature is an overload protection device (OLPD) installed in the hoist. 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 August 5, 2025. </EFFDATE> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Scott Johnson, Mechanical Systems Section, AIR-623, Technical Policy Branch, Policy and Standards Division, Aircraft Certification Service, Federal Aviation Administration, telephone 202-267-4644; email <E T="03">Scott.R.Johnson@faa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Background</HD> On September 21, 2021, Carson applied for an amendment to supplemental type certificate (STC) No. SR02507NY to add a hoist with an OLPD to be installed on Sikorsky Model S-61A, S-61L, and S-61N (including those modified by STC No. SH640NE, which shortens the S-61N by 50 inches) helicopters. The Model S-61 helicopters subject to these special conditions, currently approved under Type Certificate Nos. H2EA and 1H15, are twin-engine rotorcraft. The maximum takeoff weight is between 19,000 and 22,000 pounds, depending on configuration, and the helicopter has a maximum capacity of 39 passengers and a crew of 2. <HD SOURCE="HD1">Type Certification Basis</HD> Under the provisions of § 21.101, Carson must show that the helicopters for which it makes application to modify by STC No. SR02507NY, as changed, continue to meet the applicable provisions of the regulations listed in each helicopter's respective type certificate 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 ( <E T="03">e.g.,</E> 14 CFR part 29) do not contain adequate or appropriate safety standards for the Sikorsky Model S-61A, S-61L, and S-61N (including those modified by STC No. SH640NE) helicopters 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 Sikorsky Model S-61A, S-61L, and S-61N (including those modified by STC No. SH640NE) helicopters must comply with the exhaust-emission requirements of part 34 and the noise-certification requirements of part 36. The FAA issues special conditions, as defined in § 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 Features</HD> The Sikorsky Model S-61A, S-61L, and S-61N (including those modified by STC No. SH640NE) helicopters will incorporate the following novel or unusual design feature: An OLPD installed in a hoist. <HD SOURCE="HD1">Discussion</HD> These special conditions are necessary because regulations concerning external load carriage requirements for part 29 rotorcraft do not address hoists that include an OLPD feature. In 1991 the FAA tasked the External Load Working Group (Working Group) of the Aviation Rulemaking Advisory Committee (ARAC) with investigating the need to complement the rotorcraft 14 CFR part 133 Class D external load carriage regulations (including transport of passengers external to the rotorcraft). Upon completion of their review, the Working Group issued a report  <SU>1</SU> <FTREF/> recommending updates to the external load regulations in 14 CFR part 27 and part 29. <FTNT> <SU>1</SU>  External Load Working Group report <E T="03">https://www.faa.gov/sites/faa.gov/files/advisory_rulemaking_committees/RelwgT1-12041991.pdf.</E> </FTNT> Based on the Working Group's report, the FAA recommended several changes to part 27 and part 29 to improve safety. On July 13, 1998, the FAA published a Notice of Proposed Rulemaking  <SU>2</SU> <FTREF/> (NPRM) (63 FR 37746). This NPRM proposed amendments to the airworthiness standards for rotorcraft load combination certification. The FAA issued the final rule based on this NPRM for part 27 at amendment 27-36 and part 29 at amendment 29-43; however, the revised parts 27 and 29 did not address OLPD features in hoist systems. As a result, the current §§ 27.865 and 29.865 do not address hoist systems with OLPD features. <FTNT> <SU>2</SU>  Docket No. 29277; Notice No. 98-6, “Rotorcraft Load Combination Safety Requirements.” </FTNT> The hoist being installed by Carson includes an OLPD in its design. The OLPD reduces the likelihood of the loss of rotorcraft and crew due to an entanglement of the hoist cable. Upon activation, the OLPD affords the pilot time to respond and potentially jettison the load to save the aircraft and the crew onboard. Because the OLPD activation range is less than the limit static load factor for human external cargo published in §§ 27.865 and 29.865, it introduces a risk that the cable could completely unspool ( <E T="03">i.e.,</E> loss of cargo), particularly if unspooling is not subsequently arrested once the load is reduced below the activation threshold. Despite this risk, the overall safety will be improved with the inclusion of this OLPD. Meeting the requirements of these special conditions demonstrates that the OLPD in the hoist installed by Carson will allow an OLPD activation and recapture in response to the load conditions outlined in these special conditions. By “activation” the FAA means uncommanded cable payout ( <E T="03">i.e.,</E> slippage). The FAA intends the activation range to bound payout. The FAA is requiring an activation range for these special conditions of 2.2 to 3.5 times the rated load. The functionality and activation requirement comes from SAE AS6342, “Minimum Operational Performance Standard (MOPS) for Helicopter Hoist Systems,” December 2020, section 4.7 paragraph 2. <SU>3</SU> <FTREF/> <FTNT> <SU>3</SU>  SAE AS6342 is available for purchase at <E T="03">https://saemobilus.sae.org/standards/as6342-minimum-operational-performance-standard-mops-helicopter-hoist-systems.</E> </FTNT> The OLPD must activate within the range of 2.2 to 3.5 times the rated load. These special conditions do not change the structural limit load factors specified in §§ 27.865 and 29.865. 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. In addition to the activation range explained previously, the OLPD must be designed to continue working correctly or as expected in every way ( <E T="03">i.e.,</E> function properly) when experiencing the maximum external limit load specified in §§ 27.865 and 29.865. <HD SOURCE="HD1">Discussion of Comments</HD> The FAA issued Notice of Proposed Special Conditions No. 29-24-02-SC for Sikorsky Model S-61A, S-61L, and S-61N (including those modified by STC No. SH640NE, which shortens the S-61N by 50 inches) helicopters, which published in the <E T="04">Federal Register</E> on March 26, 2025 (90 FR 13705). The FAA received comments from five commenters, including Carson, Onboard Systems, Airbus Helicopters, and the European Union Aviation Safety Agency (EASA). <HD SOURCE="HD1">Supportive Comments</HD> The FAA received a comment from an anonymous commenter, who supported the proposed special conditions without change. <HD SOURCE="HD1">Load Function</HD> Paragraph (a)(1) of the special conditions requires the OLPD to function properly. EASA requested the FAA clarify paragraph (a)(1) regarding the following points: (1) a single failure should not lead to a catastrophic event, which includes serious injury or fatality of human external cargo; and (2) the reliability of the OLPD should be in accordance with the potential failure criticality. The FAA addresses structural requirements through 14 CFR 29.571 and system requirements through 14 CFR 29.1309. The FAA's current guidance on reliability and failure criticality is contained in Advisory Circular (AC) No. 29-2C, “Certification of Transport Category Rotorcraft.” AC No. 29-2C at change 9 references ARP4761 “Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment,” which provides guidance on labeling the severity and probability and assign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 22k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━