DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2020-0792; Project Identifier 2018-SW-049-AD; Amendment
39-21368; AD 2020-26-13]
Airworthiness Directives; Sikorsky Aircraft Corporation
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
Sikorsky Aircraft Corporation (Sikorsky) Model S-92A helicopters. This
AD was prompted by seven incidents of fatigue cracks in the horizontal
stabilizer root fitting FWD (forward root fitting). This AD requires
establishing the life limit of certain part-numbered forward root
fittings, establishing the life limit of certain part-numbered
stabilizer strut fittings, repetitively inspecting certain parts, and
depending on the inspection results, removing parts from service. The
FAA is issuing this AD to address the unsafe condition on these
DATES: This AD is effective February 1, 2021.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of February 1, 2021.
ADDRESSES: For service information identified in this final rule,
contact your local Sikorsky Field Representative or Sikorsky's Service
Engineering Group at Sikorsky Aircraft Corporation, 124 Quarry Road,
Trumbull, CT 06611; telephone 1-800-946-4337 (1-800-Winged-S); email
firstname.lastname@example.org. Operators may also log on to the
Sikorsky 360 website at https://www.sikorsky360.com. You may view this
service information at the FAA, Office of the Regional Counsel,
Southwest Region, 10101 Hillwood Pkwy., Room 6N-321, Fort Worth, TX
76177. For information on the availability of this material at the FAA,
call 817-222-5110. It is also available on the internet at https://www.regulations.gov
by searching for and locating Docket No. FAA-2020-
Examining the AD Docket
You may examine the AD docket on the internet at https://www.regulations.gov
by searching for and locating Docket No. FAA-2020-
0792; or in person at Docket Operations between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays. The AD docket contains
this final rule, any comments received, and other information. The
address for Docket Operations is U.S. Department of Transportation,
Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200
New Jersey Avenue SE, Washington, DC 20590.
FOR FURTHER INFORMATION CONTACT: Dorie Resnik, Aerospace Engineer,
Boston ACO Branch, 1200 District Avenue, Burlington, Massachusetts
01803; telephone 781-238-7693; email email@example.com.
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to Sikorsky Model S-92A
helicopters with certain part-numbered horizontal stabilizer assemblies
(stabilizer assembly), certain part-numbered forward root fittings, or
certain part-numbered stabilizer strut fittings installed. The NPRM
published in the Federal Register on September 17, 2020 (85 FR 58007).
The NPRM was prompted by seven incidents of fatigue cracks in forward
root fittings. Fatigue cracking in a forward root fitting degrades the
load path and increases the load on other assembly parts, particularly
at the aft horizontal stabilizer attachment points.
The NPRM proposed to require establishing the life limit of certain
part-numbered forward root fittings and certain part-numbered
stabilizer strut fittings. The NPRM also proposed to require
repetitively inspecting each stabilizer assembly attachment bolt and
barrel nut set, each forward root fitting, each attachment fitting
including the bolt holes and fastener holes, condition of the
fasteners, and each attachment fitting mating surface. Depending on the
inspection results, the NPRM proposed to require removing parts from
service. Finally, the NPRM proposed to prohibit installing certain
stabilizer assemblies on any helicopter. The FAA is issuing this AD to
address the unsafe condition on these products.
The FAA gave the public the opportunity to participate in
developing this final rule, but the FAA did not receive any comments on
the NPRM or on the determination of the cost to the public.
The FAA reviewed the relevant data and determined that air safety
and the public interest require adopting this final rule as proposed.
Related Service Information under 1 CFR Part 51
The FAA reviewed S-92 Maintenance Manual, SA S92A-AMM-000,
Temporary Revision (TR) 55-33, dated March 24, 2020 (TR 55-33), which
adds additional part numbers (P/Ns) to the Horizontal Stabilizer--
Maintenance Practices and specifies procedures for inspecting each
forward root fitting and aft root fitting bolt holes and fasteners,
each forward and aft root fitting mating surface for wear of the
abrasion-resistant Teflon coating, procedures for chemically striping
the abrasion-resistant Teflon coating from the entire mounting pad,
applying alodine, and applying an abrasion-resistant Teflon coating.
This service information also describes procedures for removing and
installing a stabilizer (Tasks 55-11-01-900-001 and 55-11-01-900-002),
checking the torque stabilization (Task 55-11-01-280-001), and
inspecting the stabilizer and attaching hardware (Task 55-11-01-210-
004). This service information also provides assembly diagrams and
lists interchangeable stabilizer P/Ns and compatible strut P/Ns.
This service information is reasonably available because the
interested parties have access to it through their normal course of
business or by the means identified in the ADDRESSES section.
Other Related Service Information
The FAA also reviewed S-92 Maintenance Manual SA S92A-AWL-000, TR
No. 4-58, dated October 2, 2017 (TR 4-58), and S-92 Maintenance Manual
SA S92A-AWL-000, TR No. 4-66 dated November 20, 2019 (TR 4-66). This
service information revises Task 4-00-00-200-000, Table 1 Replacement
Schedule, dated November 30, 2015. Both TR 4-58 and 4-66 revise the
Airworthiness Limitations Schedule by removing certain part-numbered
components, introducing new part-numbered components,
and establishing replacement intervals and
recurring inspections for the forward root fitting and the horizontal
stabilizer strut fitting. TR 4-58 also specifies inspecting the
horizontal stabilizer and attaching hardware at a recurring interval of
250 hours time in service (TIS).
Differences Between This AD and the Service Information
The service information requires returning affected parts to a
Sikorsky specialist; this AD does not.
Costs of Compliance
The FAA estimates that this AD affects 85 helicopters of U.S.
registry. Labor costs are estimated at $85 per work-hour. Based on
these numbers, the FAA estimates the following costs to comply with
Visually inspecting the stabilizer assembly and attached hardware
will take about 3 work-hours for an estimated cost of $255 per
helicopter and $21,675 for the U.S. fleet per inspection cycle.
If required, replacing a hat bushing and both upper fittings and
lower fittings will take about 1 work-hour and parts will cost about
$10,000 for an estimated cost of $10,085 per replacement.
If required, replacing the upper and lower support strut rod ends,
including lug and conical fitting, will take about 1 work-hour and
parts will cost about $10,000 for an estimated cost of $10,085 per
If required, performing a fluorescent penetrant inspection will
take about 3 work-hours for an estimated cost of $255 per inspection.
If required, replacing a stabilizer assembly will take about 6
work-hours and parts will cost about $312,000 for an estimated cost of
$312,510 per replacement.
If required, replacing a forward root fitting will take about 10
work-hours and parts will cost about $25,000 for an estimated cost of
$25,850 per replacement.
If required, replacing a stabilizer strut fitting will take about
10 work-hours and parts will cost about $10,000 for an estimated cost
of $10,850 per replacement.
If required, replacing a forward root fitting and an aft attachment
fitting will take about 20 work-hours and parts will cost about $50,000
for an estimated cost of $51,700 per replacement.
If required, removing wear or corrosion and applying corrosion
preventative compound will take about 0.5 work-hour and parts will cost
a nominal amount for an estimated cost of $43 per action.
If required, replacing a stabilizer attachment bolt and barrel nut
set will take about 1 work-hour and parts will cost about $500 for an
estimated cost of $585 per replacement.
If required, replacing a fastener will take about 0.1 work-hour and
parts will cost a nominal amount for an estimated cost of $9 per
If required, removing the abrasion-resistant Teflon coating to
inspect each forward and aft attachment fitting mating surface will
take about 5 work-hours for an estimated cost of $425 per inspection.
If required, applying alodine or equivalent and applying abrasion-
resistant Teflon coating will take about 5 work hours with minimal
parts cost for an estimated cost of $425 per application.
According to Sikorsky, some of the costs of this AD may be covered
under warranty, thereby reducing the cost impact on affected
individuals. The FAA does not control warranty coverage for affected
individuals. As a result, the FAA has included all costs in this cost
Authority for This Rulemaking
Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs,
describes in more detail the scope of the Agency's authority.
The FAA is issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701: General requirements.
Under that section, Congress charges the FAA with promoting safe flight
of civil aircraft in air commerce by prescribing regulations for
practices, methods, and procedures the Administrator finds necessary
for safety in air commerce. This regulation is within the scope of that
authority because it addresses an unsafe condition that is likely to
exist or develop on products identified in this rulemaking action.
This AD will not have federalism implications under Executive Order
13132. This AD will not have a substantial direct effect on the States,
on the relationship between the national government and the States, or
on the distribution of power and responsibilities among the various
levels of government.
For the reasons discussed above, I certify that this AD:
(1) Is not a "significant regulatory action" under Executive Order 12866,
(2) Will not affect intrastate aviation in Alaska, and
(3) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
Adoption of the Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 14 CFR part 39 as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. The FAA amends Sec. 39.13 by adding the following new airworthiness