[Federal Register Volume 90, Number 148 (Tuesday, August 5, 2025)]
[Rules and Regulations]
[Pages 37373-37376]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-14779]
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Rules and Regulations
Federal Register
________________________________________________________________________
This section of the FEDERAL REGISTER contains regulatory documents
having general applicability and legal effect, most of which are keyed
to and codified in the Code of Federal Regulations, which is published
under 50 titles pursuant to 44 U.S.C. 1510.
The Code of Federal Regulations is sold by the Superintendent of Documents.
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Federal Register / Vol. 90, No. 148 / Tuesday, August 5, 2025 / Rules
and Regulations
[[Page 37373]]
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.
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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 [email protected].
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 Sec. 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 Sec. 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
Sec. 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 Sec. 11.19, in
accordance with Sec. 11.38, and they become part of the type
certification basis under Sec. 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.
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\1\ External Load Working Group report https://www.faa.gov/sites/faa.gov/files/advisory_rulemaking_committees/RelwgT1-12041991.pdf.
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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 Sec. Sec.
27.865 and 29.865 do not address hoist systems with OLPD features.
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\2\ Docket No. 29277; Notice No. 98-6, ``Rotorcraft Load
Combination Safety Requirements.''
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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
[[Page 37374]]
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 Sec. Sec. 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\
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\3\ SAE AS6342 is available for purchase at https://saemobilus.sae.org/standards/as6342-minimum-operational-performance-standard-mops-helicopter-hoist-systems.
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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 Sec. Sec. 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 Sec. Sec. 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.
The FAA agrees. Paragraph (a)(2) of the special condition already
requires a minimum activation range of 2.2 times
[[Page 37375]]
the rated load. No changes are necessary as a result of this comment.
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 Sec.
29.865(a) maximum external limit load.
(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.
[[Page 37376]]
(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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