DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0653; Project Identifier AD-2021-00170-R;
Amendment 39-21784; AD 2021-22-11]
RIN 2120-AA64

Airworthiness Directives; MD Helicopters Inc. (MDHI) 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 MD Helicopters Inc. (MDHI), Model 369D, 369E, 369F, 369FF,
369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters. This AD was
prompted by a report of a spiral crack in the pilot-to-copilot tail
rotor torque tube (torque tube). This AD requires 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 issuing this
AD to address the unsafe condition on these products.

DATES: This AD is effective January 10, 2022.
The Director of the Federal Register approved the incorporation by
reference of certain documents listed in this AD as of January 10,
2022.

ADDRESSES: For service information identified in this final rule,
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. Service Information that is
incorporated by reference is also available at https://www.regulations.gov
by searching for and locating Docket No. FAA-2021-0653.

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 final rule, any
comments received, and other information. The street 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: 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:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to MDHI Model 369D, 369E,
369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters, with
torque tube part number 369H7531-9/-11/-13, installed. The NPRM
published in the Federal Register on August 13, 2021 (86 FR 44652). In
the NPRM, the FAA proposed to 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, the NPRM
proposed to require repeating the borescope inspection. If there is a
crack, elongation, or other damage, the NPRM proposed to require
removing the torque tube from service. The NPRM 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.

Discussion of Final Airworthiness Directive

Comments

The FAA received no comments on the NPRM or on the determination of
the costs.

Conclusion

The FAA reviewed the relevant data and determined that air safety
requires adopting this AD as proposed. Accordingly, the FAA is issuing
this AD to address the unsafe condition on these products. Except for
minor editorial changes, this AD is adopted as proposed in the NPRM.
The minor editorial changes include updating the cross reference in
Note 2 from ``paragraph (g)(1)(ii)'' to ``paragraph (g)(1)(ii) of this
AD,'' and deleting paragraph ``(i) No Reporting Requirement'' of the
published NPRM because it is unnecessary. As a result of deleting that
paragraph, some paragraph identifiers have changed.

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 (co-published as one document and collectively
referred to as ``Revision 2''). 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.
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 ADDRESSES.

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 (co-published as one document and collectively
referred to as ``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 (co-published
as one document and collectively referred to as ``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.

Differences Between This 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 AD requires 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
information specifies an initial compliance time of within 5 hours of
flight time, whereas this AD requires 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 AD requires removing the torque tube from
service instead. Revision 2 of the service information specifies
completing a Service Operation Report, whereas this AD does not include
that requirement.

Costs of Compliance

The FAA estimates that this AD affects 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 AD.
Visually inspecting the torque tube takes a minimal amount of time.
Borescope inspecting the torque tube takes 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 takes about 5 work-hours and
parts 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 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 helicopters 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.

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: