DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-8501; Product Identifier 2014-SW-042-AD; Amendment
39-19678; AD 2019-13-05]
RIN 2120-AA64

Airworthiness Directives; Sikorsky Aircraft Corporation
Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain Sikorsky Aircraft Corporation (Sikorsky) Model S-92A
helicopters. This AD was prompted by fatigue analysis indicating stress
concentrations, as well as the discovery of a helicopter with a crack
in the station (STA) 362 frame and skin. This AD requires inspecting
the main transmission forward and aft frame assemblies and adjacent
skins for a crack and loose fasteners, and establishing life limits for
certain frame assemblies. The FAA is issuing this AD to address the
unsafe condition on these products.

DATES: This AD is effective August 29, 2019.

ADDRESSES: For service information identified in this final rule,
contact Sikorsky Aircraft Corporation, Customer Service Engineering,
124 Quarry Road, Trumbull, CT 06611; telephone 1-800-Winged-S or 203-
416-4299; email: wcs_cust_service_eng.gr-sik@lmco.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.

Examining the AD Docket

You may examine the AD docket on the internet at http://www.regulations.gov
gov by searching for and locating Docket No. FAA-2016-
8501; 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, the regulatory evaluation, 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: Kristopher Greer, Aviation Safety
Engineer, Boston ACO Branch, Compliance and Airworthiness
Division, 1200 District Avenue, Burlington, Massachusetts 01803;
telephone (781) 238-7799; email Kristopher.Greer@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to certain Sikorsky Model
S-92A helicopters. The NPRM published in the Federal Register on July
15, 2016 (81 FR 46002). The NPRM was prompted by a fatigue analysis
that indicates stress concentrations may develop at the steel doublers
on the main transmission airframe support structure top deck, adjacent
to the transmission feet. Additionally, a helicopter was discovered
with a crack in the STA 362 frame and skin. The NPRM proposed to
require inspecting the main transmission forward and aft frame
assemblies and adjacent skins for a crack and loose fasteners, and
replacing or repairing any cracked part or loose fastener. The NPRM
also proposed to require establishing life limits for certain frame assemblies.

The FAA issued a supplemental NPRM (SNPRM) (83 FR 66167, December
26, 2018) that proposed to revise the NPRM by increasing the estimated
costs of compliance and removing the daily inspection requirements.

The FAA is issuing this AD to detect a crack in a main transmission
airframe support structure, which could result in failure of a main
transmission frame and subsequent loss of control of the helicopter.

Comments

The FAA gave the public the opportunity to participate in
developing this final rule. The following presents the comments
received on the SNPRM and the FAA's response to each comment.

Request To Reference the Latest Service Information

Sikorsky requested that the FAA reference the latest revision of
Sikorsky S-92A-AMM-000 Maintenance Manual, Chapter 53-20-00, Task 53-
20-00-210-003, "Inspection of Main Transmission Airframe Support Structure."

The FAA agrees. The FAA has revised this final rule to reference
Sikorsky S-92A-AMM-000 Maintenance Manual, Chapter 53-20-00, Task 53-
20-00-210-003, "Inspection of Main Transmission Airframe Support
Structure," dated November 30, 2018.

Request To Revise Certain Terminology in the SNPRM

Sikorsky requested that all instances of "life limits" be changed
to "replacement intervals." Sikorsky stated that this terminology is
consistent with 14 CFR Appendix A to part 29 and the approved
airworthiness limitations section of the maintenance manual.

The FAA disagrees. The term "life limit" has been used in
previous ADs applicable to Sikorsky aircraft and is well understood by
the aviation industry. In addition, the use of life limit conveys the
mandatory nature of the replacement intervals. The FAA has not changed
this final rule in this regard.

Request To Revise the Life Limit Hours Time-In-Service (TIS) in the SNPRM

Sikorsky requested that the FAA revise the values for the life
limit hours TIS. Sikorsky stated that the replacement intervals for the
frame assembly part numbers shown in table 1 to paragraph (e)(1) of the
SNPRM (which is referred to as figure 1 to paragraphs (a) and (e) in
this final rule) increased since issuance of the NPRM. Sikorsky also
stated that a recent certification effort for these parts increased the
replacement intervals by a minimum of 7,900 hours, to as much as 17,400
hours, above the limits proposed in the SNPRM. Sikorsky commented that
incorporation of these new replacement intervals (ranging from 18,300
life limit hours TIS to 29,400 life limit hours TIS, as applicable)
will avoid unnecessary removal from service of frame assemblies and
avoid the need for issuance of alternate methods of compliance to
address differences between the life limits proposed by the SNPRM and
those subsequently approved by the FAA.

The FAA agrees. The FAA has revised the life limits in this final
rule for the reasons provided by the commenter because these longer
life limits have been approved by the FAA.

Sikorsky further commented that with approval of recent
certification work, Forward STA 328 frame assemblies that are altered
and changed to P/N 92070-20124-064, 92070-20124-067, 92070-20127-045,
92070-20124-065, 92070-20124-047, or 92070-20127-046 are no longer
counted from TIS of alternation. They are only counted from the
original frame part number initial service date instead. These part-
numbered assemblies were proposed in the SNPRM for removal from service
upon accumulating 12,000 hours TIS from the alteration or 28,500 hours
TIS total (regardless of part number) from the total original frame
part number initial service date, whichever occurs first.

The FAA agrees and has omitted "remove from service of upon
accumulating 12,000 hours TIS from the alteration" in this final rule.

Additional Changes Made in This Final Rule

The four tables in the SNPRM have been re-identified as figures in
this AD. The FAA has also relocated these figures to all follow
paragraph (a) of this AD.

FAA's Determination

The FAA has reviewed the relevant information, considered the
comments received, and determined that an unsafe condition exists and
is likely to exist or develop on other helicopters of the same type
design and that air safety and the public interest require adopting the
AD requirements as proposed with the changes described previously.
These changes are consistent with the intent of the proposals in the
SNPRM and do not add any additional burden upon the public than was
already proposed in the SNPRM. Additionally, these changes will not
increase the economic burden on any operator or increase the scope of
the AD.

Related Service Information

Sikorsky issued Alert Service Bulletin (ASB) 92-53-008, Basic
Issue, dated June 13, 2012 (ASB 92-53-008); ASB 92-53-009, Basic Issue,
dated December 6, 2012 (ASB 92-53-009); ASB 92-53-012, Basic Issue,
dated February 10, 2014 (ASB 92-53-012); and S-92A-AMM-000 Maintenance
Manual, Chapter 53-20-00, Task 53-20-00-210-003, "Inspection of Main
Transmission Airframe Support Structure," dated November 30, 2018
(Task 53-20-00-210-003).

ASB 92-53-008 provides procedures for a one-time inspection of the
main transmission frames and beams for a crack, missing or loose
fastener or collar, damage, deformation, and corrosion. ASB 92-53-009
specifies, among other actions, a recurring 150-hour inspection of the
interior and exterior surfaces of the upper flanges and beams. ASB 92-
53-012 specifies altering the forward and aft transmission support
frames by removing steel doublers, cold-working the holes, oversizing
the holes, trimming skin panels, and reassembling the parts with
interference fit fasteners in accordance with Special Service
Instructions 92-074-E. After this alteration, the parts are re-
identified with a new part number. Sikorsky refers to this alteration
as a service life
extension program modification. Task 53-20-00-210-003 describes
procedures for an inspection of the main transmission airframe support
structure.

Differences Between This AD and the Service Information

The service information recommends providing certain information to
Sikorsky, and this AD does not. The service information specifies
performing a fluorescent penetrant inspection if there is a suspected
crack and contacting Sikorsky if there is a crack, while this AD only
requires repairing or replacing any cracked part. Contacting Sikorsky
is not required by this AD.

Costs of Compliance

The FAA estimates that this AD affects 50 helicopters of U.S.
Registry. The FAA estimates that operators may incur the following
costs to comply with this AD. Labor costs are estimated at $85 per
work-hour.

The FAA estimates a minimal cost to establish and revise the life
limit of the frame assembly. The FAA estimates it takes 1 work-hour to
inspect STA 328 and 362 frames. No parts are needed for a total cost of
$4,250 for the U.S. fleet for each inspection per inspection cycle. If
a fastener is replaced, the FAA estimates the cost to be minimal. If a
frame is replaced, it takes 5,000 work-hours and required parts cost
$296,000 for a total cost of $721,000 per helicopter.

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.

Regulatory Findings

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
reference, Safety.

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
directive (AD):