DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2020-0792; Product Identifier 2018-SW-049-AD]
Airworthiness Directives; Sikorsky Aircraft Corporation
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
SUMMARY: The FAA proposes to adopt a new airworthiness directive
for Sikorsky Aircraft Corporation (Sikorsky) Model S-92A helicopters.
This proposed AD was prompted by seven incidents of fatigue cracks in
the horizontal stabilizer root fitting FWD (forward root fitting). This
proposed AD would require 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. This proposed AD would also prohibit the installation of
certain parts. The FAA is proposing this AD to address the unsafe
condition on these products.
DATES: The FAA must receive comments on this proposed AD by November
ADDRESSES: You may send comments, using the procedures found in
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow
instructions for submitting comments.
Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.
Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
For service information identified in this NPRM, 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
email@example.com. 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,
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 NPRM, any comments received, and other information. The street
address for Docket Operations is listed above. Comments will be
available in the AD docket shortly after receipt.
FOR FURTHER INFORMATION CONTACT: Dorie Resnik, Aerospace Engineer,
Boston ACO Branch, 1200 District Avenue, Burlington, Massachusetts
01803; telephone 781-238-7693; email firstname.lastname@example.org.
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. The most helpful comments reference a
specific portion of the proposal, explain the reason for any
recommended change, and include supporting data. To ensure the docket
does not contain duplicate comments, commenters should send only one
copy of written comments, or if comments are filed electronically,
commenters should submit only one time.
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other information as described in 14 CFR
11.35, the FAA will file in the docket all comments received, as well
as a report summarizing each substantive public contact with FAA
personnel concerning this proposed rulemaking. Before acting on this
proposal, the FAA will consider all comments received on or before the
closing date for comments. The FAA will consider comments filed after
the comment period has closed if it is possible to do so without
incurring expense or delay. The FAA may change this proposal in light
of the comments received.
Confidential Business Information
Confidential Business Information (CBI) is commercial or financial
information that is both customarily and actually treated as private by
its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552),
CBI is exempt from public disclosure. If your comments responsive to
this NPRM contain commercial or financial information that is
customarily treated as private, that you actually treat as private, and
that is relevant or responsive to this NPRM, it is important that you
clearly designate the submitted comments as CBI. Please mark each page
of your submission containing CBI as "PROPIN." The FAA will treat
such marked submissions as confidential under the FOIA, and they will
not be placed in the public docket of this NPRM. Submissions containing
CBI should be sent to Dorie Resnik, Aviation Safety Engineer, Boston
ACO Branch, 1200 District Avenue, Burlington, Massachusetts 01803;
telephone 781-238-7693; email email@example.com. Any commentary that
the FAA receives which is not specifically designated as CBI will be
placed in the public docket for this rulemaking.
The FAA proposes to adopt a new AD for 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. This
proposed AD 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.
This proposed AD would require establishing the life limit of
certain part-numbered forward root fittings and certain part-numbered
stabilizer strut fittings. This proposed AD would also 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, this proposed AD would require removing parts from
service. Finally, this proposed AD would prohibit installing certain
stabilizer assemblies on any helicopter.
The proposed actions are intended to prevent a forward root fitting
remaining in service beyond its fatigue life, detect fatigue cracking
in a forward root fitting, and prevent increased load and stress
cracking in the stabilizer root fitting aft. This condition, if not
addressed, could result in failure of a forward root fitting,
separation of the stabilizer assembly from the helicopter, and
subsequent loss of control of the helicopter.
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/N) 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).
The FAA is proposing this AD after evaluating all the relevant
information and determining the unsafe condition described previously
is likely to exist or develop in other helicopters of the same type
Proposed AD Requirements
This proposed AD would require determining the total hours TIS of
the forward root fitting and the stabilizer strut fitting. This
proposed AD would require establishing a life limit of 7,900 hours TIS
for certain part-numbered forward root fittings and establishing a life
limit of 19,100 hours TIS for stabilizer strut fitting P/N 92070-20117-
041. This proposed AD would also require for certain part-numbered
stabilizer strut fittings installed, repetitively inspecting the
following at intervals not to exceed 50 hours TIS:
The hat bushing and both upper and lower fittings for a
crack, corrosion, fretting, deformation, and wear.
Both upper and lower support strut rod ends, including lug
and conical fitting, and both upper and lower attachment fittings on
the stabilizer and pylon, including the bushings, for a crack,
corrosion, fretting, deformation, and wear.
This proposed AD would also require repetitively inspecting the
following at intervals not to exceed 250 hours TIS or one year,
whichever occurs first:
Each stabilizer attachment bolt and barrel nut set for
corrosion, a crack, and damage to the threads indicated by uneven
threads, missing threads, or cross-threading.
Each forward root fitting and aft attachment fitting,
including inspecting the bolt holes and fastener holes for a crack,
wear, and corrosion, or as an alternative to detect cracks, fluorescent
penetrant inspecting (FPI) the area.
Each forward and aft attachment fitting mating surface for
wear of the abrasion-resistant Teflon coating and degradation. For the
purposes of this inspection, degradation may be indicated by fretting.
If there is any wear of the coating or fretting, this proposed AD would
require stripping the coating and performing a FPI or eddy current
inspection to inspect for a crack. If there are no cracks, this
proposed AD would require recoating the surfaces.
Depending on the inspection results, this proposed AD would require
removing parts from service before further flight.
Finally, this proposed AD would prohibit installing stabilizer
assembly P/N 92205-07400-043, 92205-07400-045, and 92205-07400-047 on
Differences Between This Proposed AD and the Service Information
The service information requires returning affected parts to a
Sikorsky specialist; this proposed AD would not.
Costs of Compliance
The FAA estimates that this proposed AD would affect 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
this proposed AD.
Visually inspecting the stabilizer assembly and attached hardware
would 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 would take about 1 work-hour and parts would 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, would take about 1 work-hour and
parts would cost about $10,000 for an estimated cost of $10,085 per
If required, performing a fluorescent penetrant inspection would
take about 3 work-hours for an estimated cost of $255 per inspection.
If required, replacing a stabilizer assembly would take about 6
work-hours and parts would cost about $312,000 for an estimated cost of
$312,510 per replacement.
If required, replacing a forward root fitting would take about 10
work-hours and parts would cost about $25,000 for
an estimated cost of $25,850 per replacement.
If required, replacing a stabilizer strut fitting would take about
10 work-hours and parts would 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 would take about 20 work-hours and parts would cost about
$50,000 for an estimated cost of $51,700 per replacement.
If required, removing wear or corrosion and applying corrosion
preventative compound would take about 0.5 work-hour and parts would
cost a nominal amount for an estimated cost of $43 per action.
If required, replacing a stabilizer attachment bolt and barrel nut
set would take about 1 work-hour and parts would cost about $500 for an
estimated cost of $585 per replacement.
If required, replacing a fastener would take about 0.1 work-hour
and parts would 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 would
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 would 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 proposed 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.
The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would 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 this proposed
1. Is not a "significant regulatory action" under Executive Order
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
The Proposed Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 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