DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0126; Project Identifier MCAI-2020-00266-R]
RIN 2120-AA64

Airworthiness Directives; Airbus Helicopters Deutschland GmbH
(AHD) Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for Airbus Helicopters Deutschland GmbH (AHD) Model MBB-BK 117 D-2
helicopters. This proposed AD was prompted by a report of a broken
Titanium (Ti) bolt. This proposed AD would require removing certain Ti-
bolts from service and prohibit installing these Ti-bolts in a critical
area. 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 April 19,
2021.

ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:

Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow the
instructions for submitting comments.

Fax: (202) 493-2251.

Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590-0001.

Hand Delivery: Deliver to Mail address between 9 a.m. and
5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this NPRM, contact Airbus
Helicopters, 2701 N Forum Drive, Grand Prairie, TX 75052; telephone
(972) 641-0000 or (800) 232-0323; fax (972) 641-3775; or at https://www.
airbus.com/helicopters/services/technical-support.html. You may
view the referenced 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.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0126; 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 European
Union Aviation Safety Agency (EASA) AD, any comments received, and
other information. The street address for Docket Operations is listed
above.

FOR FURTHER INFORMATION CONTACT: Matt Fuller, AD Program Manager,
General Aviation & Rotorcraft Unit, Airworthiness Products Section,
Operational Safety Branch, FAA, 10101 Hillwood Pkwy., Fort Worth, TX
76177; telephone (817) 222-5110; email matthew.fuller@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under ADDRESSES. Include "Docket No. FAA-2021-0126; Project Identifier
MCAI-2020-00266-R" at the beginning of your comments. The most helpful
comments reference a specific portion of the proposal, explain the
reason for any recommended change, and include
supporting data. The FAA will consider all comments received by the
closing date and may amend this proposal because of those comments.

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 post all comments received, without change, to
https://www.regulations.gov, including any personal information you
provide. The agency will also post a report summarizing each
substantive verbal contact received about this NPRM.

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 Matt
Fuller, AD Program Manager, General Aviation & Rotorcraft Unit,
Airworthiness Products Section, Operational Safety Branch, FAA, 10101
Hillwood Pkwy., Fort Worth, TX 76177; telephone (817) 222-5110; email
matthew.fuller@faa.gov. Any commentary that the FAA receives which is
not specifically designated as CBI will be placed in the public docket
for this rulemaking.

Background

EASA, which is the Technical Agent for the Member States of the
European Union, has issued EASA AD No. 2019-0258, dated October 18,
2019, to correct an unsafe condition for Airbus Helicopters Deutschland
GmbH (AHD), formerly Eurocopter Deutschland GmbH, Model MBB-BK117 D-2
helicopters. EASA advises of a report of a broken Ti-bolt. Subsequent
investigation revealed that an improper heat treatment process was
accomplished on a batch of Ti-bolts, which can lead to hydrogen
embrittlement. Hydrogen embrittlement can make high-strength bolts
susceptible to stress corrosion, pitting, and failure.

EASA states that this condition, if not detected and corrected,
could lead to failure of an affected Ti-bolt installed in a critical
location, possibly resulting in reduced control of the helicopter.
Accordingly, the EASA AD requires a one-time inspection for Ti-bolt
part number (P/N) EN3740-060022F marked with manufacturer monogram
"D" or with an illegible manufacturer monogram installed on the aft
connection of the tail rotor ball bearing control (ball bearing
control) and, depending on findings, contacting AHD for corrective
action. The EASA AD also prohibits the (re)installation of these Ti-
bolts.

FAA's Determination

These helicopters have been approved by EASA and are approved for
operation in the United States. Pursuant to the FAA's bilateral
agreement with the European Union, EASA has notified the FAA about the
unsafe condition described in its AD. The FAA is proposing this AD
after evaluating all known relevant information and determining that an
unsafe condition is likely to exist or develop on other helicopters of
the same type design.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Airbus Helicopters Alert Service Bulletin (ASB)
No. ASB MBB-BK117 D-2-00A-001, Revision 1, dated October 16, 2019 (ASB
MBB-BK117 D-2-00A-001 Rev 1), which specifies replacing each Ti-bolt P/N
EN3740-060022F that is marked with manufacturer monogram "D" or if
the manufacturer monogram cannot be identified with an airworthy Ti-
bolt in both locations of the aft connection of ball bearing control
and both HF antenna bracket locations.

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.

Proposed AD Requirements

This proposed AD would require removing any Ti-bolt P/N EN3740-
060022F marked with manufacturer monogram "D" or with an illegible
manufacturer monogram installed on the aft connection of the ball
bearing control from service. This proposed AD would also prohibit
installing an affected Ti-bolt on the aft connection of the ball
bearing control of any helicopter.

Differences Between This Proposed AD and the EASA AD

The EASA AD applies to Model MBB-BK117 D-2 helicopters and requires
inspecting for Ti-bolt P/N EN3740-060022F marked with manufacturer
monogram "D" or with an illegible manufacturer monogram installed on
the aft connection of the ball bearing control. This proposed AD
applies to Model MBB-BK 117 D-2 helicopters with a Ti-bolt P/N EN3740-
060022F marked with manufacturer monogram "D" or with an illegible
manufacturer monogram installed on the aft connection of the ball
bearing control instead. The EASA AD requires contacting AHD for
approved instructions if an affected Ti-bolt is found, whereas this
proposed AD would require removing an affected Ti-bolt from service
instead.

Costs of Compliance

The FAA estimates that this AD if adopted as proposed, would affect
29 helicopters of U.S. Registry. Labor rates are estimated at $85 per
work-hour. Based on these numbers, the FAA estimates that operators may
incur the following costs in order to comply with this proposed AD.

Replacing a Ti-bolt would take about 2 work-hours and parts would
cost about $100 for an estimated cost of $270 per Ti-bolt.

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

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, I certify this proposed regulation:

(1) Is not a "significant regulatory action" under Executive
Order 12866,

(2) Would not affect intrastate aviation in Alaska, and

(3) Would 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.

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
directive: