DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2017-1125; Product Identifier 2017-SW-078-AD; Amendment
39-19880; AD 2020-06-11]
RIN 2120-AA64

Airworthiness Directives; MD Helicopters Inc. 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 MD
Helicopters Inc. (MDHI) Model 600N helicopters. This AD requires
establishing a life limit for the main rotor (M/R) blade upper control
collective/longitudinal link assembly (link assembly). This AD was
prompted by the discovery that the life limit was omitted from the
maintenance manual. The actions of this AD are intended to prevent an
unsafe condition on these products.

DATES: This AD is effective April 28, 2020.

ADDRESSES: For service information related to this final rule, contact
MD Helicopters, Inc., Attn: Customer Support Division, 4555 E. McDowell
Rd., Mail Stop M615, Mesa, AZ 85215-9734; telephone 1-800-388-3378; fax
480-346-6813; or at https://www.mdhelicopters.com. You may review 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 on the internet at https://www.regulations.
gov by searching for and locating Docket No. FAA-2017-
1125; 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 AD, 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 and Airworthiness
Division, FAA, 3960 Paramount Blvd., Lakewood, California 90712;
telephone 562-627-5313; email payman.soltani@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 MDHI Model 600N
helicopters with a yaw stability augmentation system and with an M/R
link assembly part number (P/N) 600N7617-1 installed. The NPRM
published in the Federal Register on September 10, 2018 (83 FR 45580).
The NPRM was prompted by a report from MDHI that during a review of the
Airworthiness Limitations section of the applicable maintenance manual,
MDHI discovered that it did not include a life limit for link
assemblies installed on MDHI Model 600N helicopters with a yaw
stability augmentation system. Link assembly P/N 600N7617-1, which is
made of aluminum, is a life-limited part with a life limit of 15,000
hours time-in-service (TIS). MDHI subsequently revised the
Airworthiness Limitations section of the maintenance manual to include
the life limit. The NPRM proposed to require creating a component
history card or equivalent record for each affected link assembly, if
one does not exist, and recording a life limit of 15,000 hours TIS.
This NPRM also proposed to require determining the hours TIS of the
link assembly and removing the link assembly from service according to
the new life limit. The proposed requirements were intended to prevent
a link assembly remaining in service beyond its life limit, which could
result in fatigue failure, loss of M/R blade pitch control, and
subsequent loss of helicopter control.

Comments

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

Request

MDHI expressed concern that the requirements proposed by the NPRM
do not definitively eliminate the risk of a life limit being exceeded.
MDHI stated that link assembly P/N 600N7617-1 is not serialized and
is aware that link assemblies have been installed on aircraft with
multiple serial numbers, possibly indicating that link assemblies P/N
600N7617-1 may not have a reliable TIS record. MDHI also stated if the
TIS is unknown, arbitrarily setting the TIS to the aircraft hours may
not adequately reflect the actual TIS of link assembly P/N 600N7617-1.

FAA Response

The FAA acknowledges link assembly P/N 600N7617-1 is not serialized
and the possibility of cross-installation on multiple aircraft.
However, the FAA has determined that using the hours TIS of the
helicopter mitigates the risk to an acceptable level because there is a
small number of link assemblies P/N 600N7617-1 in-service, the usage
rate for MDHI Model 600N helicopters is similar throughout the fleet,
and the 15,000 hours TIS life limit includes a built-in life reduction
for different variabilities.

Request

MDHI requested the FAA mandate the replacement of link assembly P/N
600N7617-1 with link assembly P/N 600N7617-5. MDHI explained that
installation of link assembly P/N 600N7617-5 is consistent with
production and field modification installations of the yaw stability
augmentation system (YSAS), which requires installation of link
assembly P/N 600N7617-5, and that link assembly P/N 600N7617-5 is not
subject to life-limiting fatigue, therefore eliminating this potential
safety risk.

FAA Response

The FAA agrees that replacing link assembly P/N 600N7617-1 with
link assembly P/N 600N7617-5 is beneficial but disagrees that the
replacement is required for airworthiness. Link
assembly P/N 600N7617-5 is an upgraded part made of steel and is not
subject to a life limit. The FAA disagrees with requiring replacement
of link assembly P/N 600N7617-1 with link assembly P/N 600N7617-5
because link assembly P/N 600N7617-1 is airworthy within the life limit
of 15,000 TIS. The FAA provided additional information about this
response, which can be found in the AD docket. The FAA has added an
optional terminating action to the requirements of this AD that
specifies removing link assembly P/N 600N7617-1 from service and
installing link assembly P/N 600N7617-5 instead.

FAA's Determination

The FAA has reviewed the relevant data, considered the comments
received, and determined that air safety and the public interest
require adopting this final rule as proposed except for the changes
described previously. These changes are consistent with the intent that
was proposed in the NPRM to address the unsafe condition and do not add
any additional burden upon the public to that already proposed in the
NPRM. The FAA has also determined that these changes will neither
increase the economic burden on any operator nor increase the scope of
this final rule.

Related Service Information

The FAA reviewed MDHI CSP-HMI-2 MDHI Maintenance Manual, Chapter
04, Airworthiness Limitations, Revision 47, dated September 30, 2016.
This service information specifies a 15,000 hour TIS life limit for
link assembly P/N 600N7617-1 for helicopters with a yaw stability
augmentation system.

Costs of Compliance

The FAA estimates that this AD affects 26 helicopters of U.S.
Registry. The FAA estimates that operators may incur the following
costs in order to comply with this AD. Labor costs are estimated at $85
per work-hour.
Determining the hours TIS of each link assembly and updating the
aircraft records takes about 30 minutes, for a cost of $43 per
helicopter and $1,118 for the U.S. fleet.
Replacing a link assembly, if needed, takes about 2 work-hours, and
parts cost about $984 for an estimated replacement cost of $1,154 per
link 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):