90 FR 148 pgs. 37373-37376 - 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
Type: RULEVolume: 90Number: 148Pages: 37373 - 37376
Pages: 37373, 37374, 37375, 37376Docket number: [Docket No. FAA-2024-2383; Special Conditions No. 29-059-SC]
FR document: [FR Doc. 2025-14779 Filed 8-4-25; 8:45 am]
Agency: Transportation Department
Sub Agency: Federal Aviation Administration
Official PDF Version: PDF Version
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 29
[Docket No. FAA-2024-2383; Special Conditions No. 29-059-SC]
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
AGENCY:
Federal Aviation Administration (FAA), DOT.
ACTION:
Final special conditions.
SUMMARY:
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.
DATES:
Effective August 5, 2025.
FOR FURTHER INFORMATION CONTACT:
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 Scott.R.Johnson@faa.gov.
SUPPLEMENTARY INFORMATION:
Background
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.
Type Certification Basis
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.g., 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.
Novel or Unusual Design Features
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.
Discussion
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? 1 recommending updates to the external load regulations in 14 CFR part 27 and part 29.
Footnotes:
1 ?External Load Working Group report https://www.faa.gov/sites/faa.gov/files/advisory_rulemaking_committees/RelwgT1-12041991.pdf.
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? 2 (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.
Footnotes:
2 ?Docket No. 29277; Notice No. 98-6, "Rotorcraft Load Combination Safety Requirements."
[top] 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
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 ( i.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 ( i.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. 3
Footnotes:
3 ?SAE AS6342 is available for purchase at https://saemobilus.sae.org/standards/as6342-minimum-operational-performance-standard-mops-helicopter-hoist-systems.
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 ( i.e., function properly) when experiencing the maximum external limit load specified in §§?27.865 and 29.865.
Discussion of Comments
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 Federal Register 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).
Supportive Comments
The FAA received a comment from an anonymous commenter, who supported the proposed special conditions without change.
Load Function
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 assigning an assurance level requirement for which to hold the applicant accountable.
Load Limits
Airbus Helicopters, Onboard Systems, and Carson requested the FAA revise the special conditions to define activation consistent with SAE AS6342. Onboard Systems stated activation should be limited to the OLPD static response, and the OLPD dynamic response should be characterized or demonstrated through tests in SAE AS6342 Section 5.1.9.1. Carson requested the FAA define activation solely as the initiation of slip (static slip point). Airbus Helicopters stated that while the lower limit of the activation band can be well controlled, the upper limit may be higher than 3.2 times the rated load, that the 3.2 value is arbitrary, and that any upper limit should be justified depending on the undesired event the OLPD is designated for. Airbus Helicopters further stated that in this context, the upper limit as specified in paragraph (a)(2) of the special conditions appears to be redundant with paragraph (a)(3)(i). Airbus Helicopters and Onboard Systems expressed concern that, under the special conditions as written, existing hoist/OLPD designs would be ineligible for installation certification and new designs would be unable to meet the requirements.
The FAA agrees and has revised the Discussion section to clarify that "activation" means uncommanded cable payout ( i.e., slippage). The FAA also agrees that the proposed maximum limit of the activation range tolerance is too restrictive for both OLPD activation and recapture and has revised paragraph (a)(2) of the special conditions to change the activation range to 2.2 to 3.5 times the rated load. The FAA has also added a requirement to paragraph (a)(2) that recapture must occur before the load falls below 2.2 times the rated load (2.2 or greater). Paragraph (a)(3)(i) of the special conditions requires that the OLPD prevent excess cable tension that could result in cable failure or pulling the aircraft into an unrecoverable attitude.
The FAA notes that it did not choose the proposed 3.2 value arbitrarily. Over several years of discussions among the FAA, EASA, and industry, 3.2 was determined to be an appropriate value that would provide enough protection from cable failure due to excessive loads. This number also keeps the energy from a broken cable low enough to prevent the cable from rebounding into the rotor system. However, as previously explained, the FAA has increased the limit to 3.5 times the rated load to provide additional range to the tolerance band. Regarding the comment on justification for the upper limit setting, the FAA has determined that the minimum operational performance for OLPD is that it must prevent excess cable tension that might result in cable failure or loads on the helicopter that endanger the aircraft. Paragraphs (a)(2) and (a)(3)(i) are two separate requirements. Paragraph (a)(2) establishes a maximum hoist design point, while paragraph (a)(3) contains installation level requirements protecting the aircraft and HEC. EASA requested the FAA evaluate whether the minimum load factor of 2.2 is sufficiently above the normal operational load to prevent the activation of the OLPD during normal operation.
The FAA acknowledges the comment and finds the 2.2 load factor acceptable, as established and published in SAE AS6342. No changes were made as a result of this comment.
Carson recommended that OLPD activation must not occur below 2.2 times the rated load to prevent unintentional OLPD activation.
[top] The FAA agrees. Paragraph (a)(2) of the special condition already requires a minimum activation range of 2.2 times
Carson recommended the FAA revise paragraph (a)(3)(iv) of the proposed special conditions to address arresting cable slip (recapture) separately.
The FAA agrees. The Discussion section of the proposed special conditions defined activation as all states of its intended function (uncommanded cable payout and recapture). The FAA has revised the Discussion section of these final special conditions to limit the definition of activation as cable payout (slippage). Recapture is a separate event from OLPD activation. Recapture must occur before the load falls below 2.2 times the rated load as stated in paragraph (a)(2).
Aging Factors
EASA stated that the proposed special conditions do not address the aging of the OLPD through time or through an OLPD activation event and that friction material could degrade over time, which could lower the OLPD set point below the prescribed value. EASA requested the FAA revise the proposed special conditions to account for these factors.
The FAA agrees and has revised paragraph (a)(2) of the special conditions to clarify that production and maintenance tolerances include aging and wear considerations.
Design Activation Limits
EASA requested the FAA clarify that "design activation limit ( i.e. defined set point(s))" in paragraph (a)(3) of the proposed special conditions corresponds to the activation range in paragraph (a)(2).
The FAA concurs with EASA that the "design activation limit ( i.e. defined set point(s))" corresponds to the activation range and added clarification to the special condition.
Airbus Helicopters commented that the OLPD effectivity may be impacted when the hoist-cable is fully reeled-out due to the cable being attached to the drum. Airbus Helicopters stated that in this condition, the load required to break the cable off the drum can be even higher than the OLPD upper activation limit.
The FAA disagrees. The OLPD would not be further impacted from the cable being fixed to the drum causing even higher loads to break the cable from the drum. There is a minimum requirement of cable wraps around the drum determined by the hoist manufacturers that must be present in order to maintain load capacity.
Airbus Helicopters commented that with state-of-the-art hoists available on the market, arresting the cable after a triggering event may occur close to or slightly below the lower OLPD activation limit due to the physics of friction. Airbus Helicopters further stated that the time or cable-length to arrest the load after an activation event is dependent on various conditions, such as actual payload, cable-length, cable-reeling (slipping) speed, and temperature.
The FAA disagrees that the hoist will not recapture below 2.2 times the rated load. Industry set this condition in SAE AS6342 Section 4.7. The FAA will not certify a hoist installation that allows the load to go below 2.2 times the rated load.
Out of Scope Comments
The FAA received some comments that were beyond the scope of the proposed special conditions. The FAA did not make any changes as a result of these comments.
EASA requested the FAA revise the proposed special conditions to include a requirement that the cable sustain a minimum load of 3.2g.
These special conditions address the OLPD installed on the hoist system and do not address the cable. The cable is part of the hoist critical load path and is addressed through compliance with 14 CFR 29.865 and other relevant regulations within 14 CFR part 29 Subparts C and D.
EASA requested the FAA revise paragraph (a)(3)(iv) of the proposed special conditions to include a maximum unspooling length before arresting the human external cargo (HEC) and a maximum arresting load similar to the one in the EASA ETSO-2C208 paragraph 5.1.9.1.2. EASA expressed concern that a full cable unspooling or significant shock load from the cable arresting could cause injury to the HEC.
The FAA disagrees. While the FAA acknowledges the comment that human external cargo could experience bodily injury from a full cable unspooling or shock loads from recapture, these conditions are out of scope for these special conditions. These events are speculative, and the FAA does not have data to support this happens regularly during operations in the field.
Except as discussed above and in the Summary of Changes, the special conditions are adopted as proposed.
Applicability
As discussed above, these special conditions are applicable to the Model S-61 helicopters listed on the approved model list (AML) of STC No. SR02507NY, which is available at https://drs.faa.gov/. Should Carson apply at a later date for a change to STC No. SR02507NY to include any other model on the AML 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 Federal Register . However, as the certification date 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, as modified by Carson, is imminent, the FAA finds that good cause exists to make these special conditions effective upon publication.
Conclusion
This action only affects certain novel or unusual design features for the helicopters listed on the AML of STC No. SR02507NY. 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.
List of Subjects in 14 CFR Part 29
Aircraft, Aviation safety, Reporting and recordkeeping requirements.
Authority Citation
The authority citation for these special conditions is as follows:
Authority:
49 U.S.C. 106(f), 106(g), 40113, 44701, 44702, 44704.
The Special Conditions
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 Sikorsky Model S-61A, S-61L, and S-61N, and S-61N (including those modified by STC No. SH640NE) helicopters listed on the AML of STC No. SR02507NY, as modified by Carson.
(a) The Overload Protection Device (OLPD) must:
(1) Function properly for all loads up to and including the §?29.865(a) maximum external limit load.
[top] (2) Be designed to hold any load up to 2.2 times the rated load and shall activate between 2.2 times the rated load and 3.5 times the rated load. This activation range must take into account production and maintenance tolerances (including aging and wear considerations), variations due to the environment ( e.g., temperature and humidity), and operations ( e.g., length of cable paid out). The above requirements must be met over the entire activation range. Recapture must never be below 2.2 times the rated load.
(3) Protect the helicopter and cargo by incorporating design activation limits ( i.e., defined set point(s) established in paragraph (a)(2)) which:
(i) Prevent excess cable tension that might result in cable failure or loads on the helicopter that endanger the aircraft,
(ii) Prevent uncommanded cable payout when experiencing cable loads below the activation range,
(iii) Allow cable payout when experiencing loads above the activation range, and
(iv) Arrest cable unspooling to prevent loss of cargo after an activation event.
(b) The OLPD installation, maintenance, and inspection instructions must be made a part of the applicable section(s) of the Instructions for Continued Airworthiness (ICA).
Issued in Des Moines, Washington, on July 31, 2025.
Michael T. Thompson,
Acting Manager, Technical Policy Branch, Policy and Standards Division, Aircraft Certification Service.
[FR Doc. 2025-14779 Filed 8-4-25; 8:45 am]
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