DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0653; Project Identifier AD-2021-00170-R]
RIN 2120-AA64

Airworthiness Directives; MD Helicopters Inc. (MDHI) 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 MD Helicopters Inc. (MDHI), Model 369D, 369E, 369F, 369FF, 369H,
369HE, 369HM, 369HS, 500N, and 600N helicopters. This proposed AD was
prompted by a report of a spiral crack in the pilot-to-copilot tail
rotor torque tube (torque tube). This proposed AD would require a one-
time visual and recurring borescope inspections of the torque tube and
depending on the results, removing the torque tube from service. 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 September
27, 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.

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 MD
Helicopters, Inc., Attn: Customer Support Division, 4555 E McDowell
Rd., Mail Stop M615, Mesa, AZ 85215-9734; telephone (800) 388-3378; fax
(480) 346-6813; or at https://www.mdhelicopters.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.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0653; 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.

FOR FURTHER INFORMATION CONTACT: Payman Soltani, Aerospace Engineer,
Airframe Section, Los Angeles ACO Branch, Compliance & Airworthiness
Division, FAA, 3960 Paramount Blvd., Lakewood, CA 90712; telephone
(562) 627-5313; email payman.soltani@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-2021-0653; Project Identifier
AD-2021-00170-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
Payman Soltani, Aerospace Engineer, Airframe Section, Los Angeles ACO
Branch, Compliance & Airworthiness Division, FAA, 3960 Paramount Blvd.,
Lakewood, CA 90712; telephone (562) 627-5313; email
payman.soltani@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

The FAA proposes to adopt a new AD for MDHI Model 369D, 369E, 369F,
369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters. This
proposed AD would require a one-time visual and recurring borescope
inspections of the torque tube and depending on the results, removing
the torque tube from service. This proposed AD was prompted by a report
of a spiral crack in the torque tube that appears to have originated
from a hole where the tail rotor torque tube control fitting attaches
to the torque tube on a Model 369FF helicopter. This crack resulted in
increased left pedal movement and subsequent reduced directional
control pedal authority. Other model helicopters are affected due to
design similarity. This condition, if not addressed, could result in
failure of the torque tube, loss of tail rotor control, and subsequent
loss of control of the helicopter.

FAA's Determination

The FAA is issuing this NPRM after determining that the unsafe
condition described previously is likely to exist or develop on other
products of these same type designs.

Related Service Information Under 1 CFR Part 51

The FAA reviewed MD Helicopters Service Bulletin SB369D-229R2 for
Model 369D helicopters, SB369E-129R2 for Model 369E helicopters,
SB369F-119R2 for Model 369F and 369FF helicopters, SB369H-263R2 for
Model 369H, 369HE, 369HM, and 369HS helicopters, SB500N-066R2 for Model
500N helicopters, and SB600N-080R2 for Model 600N helicopters, each
dated March 24, 2021 (Revision 2). These service bulletins are co-
published as one document. Revision 2 of this service information
specifies procedures for a one-time visual inspection and recurring
borescope inspections, completing a Service Operation Report, and
returning a removed torque tube to an authorized service center or
MDHI.

Other Related Service Information

The FAA also reviewed MD Helicopters Service Bulletin SB369H-263,
SB369D-229, SB369E-129, SB369F-119, SB500N-066, and SB600N-080, each
dated January 30, 2020 (initial issuance), and MD Helicopters Service
Bulletin SB369H-263R1, SB369D-229R1, SB369E-129R1, SB369F-119R1,
SB500N-066R1, and SB600N-080R1, each dated May, 15 2020 (Revision 1).
The initial issuance and Revision 1 of this service information specify
the same procedures as Revision 2 of this service information, except
Revision 1 clarified the torque value to apply to the nut and Revision
2 deletes Method 2 of the Accomplishment Instructions and adds a
recurring 300-hour borescope inspection of the torque tube.

Proposed AD Requirements in This NPRM

This proposed AD would initially require visually inspecting the
torque tube exterior using a flashlight and mirror and borescope
inspecting the interface of the torque tube and bushing segments for a
crack, elongation, and other damage, which may be indicated by any
corrosion, pitting, crazing, dents, dings, displacement of material at
the bolt hole edge, or fretting of the hole. Thereafter, this proposed
AD would require repeating the borescope inspection. If there is a
crack, elongation, or other damage, this proposed AD would require
removing the torque tube from service.

Differences Between This Proposed AD and the Service Information

For helicopters that have accumulated 600 or less total hours time-
in-service (TIS), Revision 2 of the service information specifies an
initial compliance time of during the next 100-hour inspection, whereas
this proposed AD would require initial actions within 100 hours TIS
after the effective date of this AD instead. For helicopters that have
accumulated more than 600 total hours TIS, Revision 2 of the service in-
formation specifies initial a compliance time of within 5 hours of flight
time, whereas this proposed AD would require initial actions within 5
hours TIS or 30 days after the effective date of this AD, whichever occurs
later, instead.

Revision 2 of the service information specifies returning a removed
torque tube, whereas this proposed AD would require removing the torque
tube from service instead. Revision 2 of the service information
specifies completing a Service Operation Report, whereas this proposed
AD does not include that requirement.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 58 helicopters of U.S. Registry. Labor rates 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 torque tube would take a minimal amount of
time. Borescope inspecting the torque tube would take about 1 work-hour
for an estimated cost of $85 per helicopter and $4,930 for the U.S.
fleet, per inspection cycle.

If required, replacing the torque tube would take about 5 work-
hours and parts would cost about $983 for an estimated cost of $1,408
per helicopter.

The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some of the costs of this
proposed AD may be covered under warranty, thereby reducing the cost
impact on affected operators.

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: