DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2019-0663; Product Identifier 2018-SW-057-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 certain Sikorsky Aircraft Corporation (Sikorsky) Model S-70, S-70A,
S-70C, S-70C(M), and S-70C(M1) helicopters. This proposed AD was
prompted by four incidents of disbonding between the tail rotor (T/R)
blade pitch horn and the torque tube. This proposed AD would require
recurring visual and tap inspections of the T/R blade, and depending on
the outcome, replacing the T/R blade. 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 October
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 http://www.regulations.gov. Follow the
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-Winged-S or (203) 416-4299; email
email@example.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)
Examining the AD Docket
You may examine the AD docket on the internet at http://www.regulations.
gov by searching for and locating Docket No. FAA-2019-
0663; 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, the regulatory evaluation, 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: Kristopher Greer, Aviation Safety
Engineer, Boston ACO Branch, Compliance & Airworthiness Division, FAA,
1200 District Avenue, Burlington, MA 01803; telephone (781) 238-7799;
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under the ADDRESSES section. Include "Docket No. FAA-2019-0663;
Product Identifier 2018-SW-057-AD" at the beginning of your comments.
The FAA specifically invites comments on the overall regulatory,
economic, environmental, and energy aspects of this NPRM. The FAA will
consider all comments received by the closing date and may amend this
NPRM because of those comments.
The FAA will post all comments the FAA receives, without change, to
http://www.regulations.gov, including any personal information you
provide. The FAA will also post a report summarizing each substantive
verbal contact the FAA receives about this NPRM.
The FAA proposes to adopt a new AD for Sikorsky Model S-70, S-70A,
S-70C, S-70C(M), and S-70C(M1) helicopters with T/R blade part number
70101-31000 (all dash numbers) and with a serial number up to and
This proposed AD is prompted by four incidents of disbonding
between the T/R blade pitch horn and the torque tube on Model UH-60L
and SH-60F helicopters. The disbonding produced minor to severe
vibrations due to the mass imbalance. This condition may also occur on
Sikorsky Model S-70, S-70A, S-70C, S-70C(M), and S-70C(M1) helicopters
due to design similarity.
Disbonding between the T/R blade pitch horn and the torque tube, if
not addressed, could result in the T/R blade pitch horn rocking in the
torque tube, leading to increased T/R vibrations. These vibrations
could lead to crushing of the torque tube and subsequent loss of
control of the helicopter. While Sikorsky continues to test T/R blades
returned from the field, investigation has revealed blades produced
prior to manufacturing improvements implemented between 2006 and 2007
are prone to this disbonding. To address this condition, Sikorsky is
assessing design change options to retrofit the affected T/R blades.
Related Service Information
The FAA reviewed Sikorsky Aircraft Model S-70 Blackhawk Derivatives
Maintenance Manual Temporary Revision No. 72, dated October 12, 2017.
This service information specifies replacing a 10-hour/14-day T/R
inspection with a before first flight of the day T/R inspection.
The FAA also reviewed section 5-3-13.2 Coin-Tapping Inspection
Method of Sikorsky Technical Manual TM 1-70-23-3, Change 12, dated July
1, 2018. This service information specifies procedures for coin-tap
inspecting T/R blades. This service information also specifies general
repair limits and includes figures illustrating the different types of
materials of the T/R blade skin and core regions.
The FAA is proposing this AD because the FAA evaluated all the
relevant information and determined the unsafe condition described
previously is likely to exist or develop in other products of these
same type designs.
Proposed AD Requirements
This proposed AD would require, before the first flight of each
day, visually inspecting each T/R blade for any crack, leading edge
erosion, and trailing edge skin disbonding and separation, paying
particular attention to the area from the midspan to the pitch control
horn; and tap inspecting for disbonding in the pitch horn to torque tube
bond area. Depending on the outcome of these inspections, this proposed
would require replacing the T/R blade.
The FAA considers this proposed AD interim action. The design
approval holder is currently developing a modification that will
address the unsafe condition identified in this AD. Once this
modification is developed, approved, and available, we might consider
Costs of Compliance
The FAA estimates that this proposed AD affects 13 helicopters of
U.S. registry. The FAA estimates the following costs to comply with
this proposed AD. Labor costs are estimated at $85 per work-hour.
Inspecting the T/R blades would take about 1 work-hour for an
estimated cost of $85 per helicopter and $1,105 for the U.S. fleet, per
inspection cycle. Replacing a set of two T/R blades would take about 6
work-hours and parts would cost about $192,304 for an estimated cost of
$192,814 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.
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
(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