DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-5595; Directorate Identifier 2015-NM-087-AD;
Amendment 39-18871; AD 2017-09-09]
RIN 2120-AA64

Airworthiness Directives; Zodiac Seats California LLC Seating
Systems

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for certain
Zodiac Seats California LLC seating systems. This AD was prompted by a
determination that the affected seating systems may cause serious
injury to the occupant during forward impacts when subjected to certain
inertia forces. This AD requires removing affected seating systems. We
are issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective June 28, 2017.

ADDRESSES:

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-2016-
5595; or in person at the Docket Management Facility between 9 a.m. and
5 p.m., Monday through Friday, except Federal holidays. The AD docket
contains this AD, the regulatory evaluation, any comments received, and
other information. The address for the Docket Office (phone: 800-647-
5527) is Docket Management Facility, 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: Patrick Farina, Aerospace Engineer,
Cabin Safety Branch, ANM-150L, FAA, Los Angeles Aircraft Certification
Office (ACO), 3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone:
562-627-5344; fax: 562-627-5210; email: patrick.farina@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 by adding an AD that would apply to certain Zodiac Seats
California LLC seating systems. The NPRM published in the Federal
Register on April 20, 2016 (81 FR 23212) (``the NPRM''). The NPRM was
prompted by a determination that the affected seating systems may cause
serious injury to the occupant during forward impacts when subjected to
certain inertia forces. The NPRM proposed to require removing affected
seating systems. We are issuing this AD to prevent serious injury to
the occupant during forward impacts in emergency landing conditions.
After the NPRM comment period closed, we reopened the comment
period to allow additional time for interested parties to comment on
the NPRM (81 FR 41466, June 27, 2016).

Comments

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

Request To Withdraw the NPRM

The Industry Ad Hoc Committee (which consists of Bombardier,
Embraer, HAECO Cabin Solutions, Zodiac Seats California, Zodiac Seats
France, Zodiac Seats UK, and Zodiac Seats US) and Zodiac Seats
California (commenting independently) questioned the basis for the
requirements of the proposed AD. We infer they are requesting we
withdraw the NPRM. The Industry Ad Hoc Committee and Zodiac Seats
California stated the proposed AD is not supported on a technical basis
and is based only on limited research. The Industry Ad Hoc Committee
asked if there have been any aerospace incidents or accidents
documenting the specific neck injuries being mitigated by the proposed
AD. The Industry Ad Hoc Committee and Zodiac Seats California stated
there has been no correlation to develop proper costs/benefits related
to the type of injury mechanism specified in the NPRM with respect to
actual accident injuries. The Industry Ad Hoc Committee and Zodiac
Seats California cited multiple accidents where news and investigative
reports from the accidents did not mention serious neck injuries.
We do not agree to withdraw the NPRM. The intent of this AD is to
provide a safe outcome for passengers during a survivable crash by
preventing serious injuries, such as a transection of the neck during
forward impacts in emergency landing conditions. We find that
sufficient data exist to demonstrate that affected seating systems
might cause serious injury to the occupant during forward impacts when
subjected to certain inertia forces. We note that the commenters have
identified several accidents that were survivable with seating systems
that are not subject to this AD. The comparison of those seating
systems to the ones identified in this AD is not valid.
We have identified an unsafe condition and determined corrective
action is required. Therefore, we have not revised this AD in this
regard. We have provided additional details on the unsafe condition in
the comment responses that follow.

Request To Revise Applicability To Exclude Seating Systems With a
Certain Design

Zodiac Seats California requested that we exclude new seating
systems that have been built with design solutions that remove the
unsafe condition. Zodiac Seats California recommended that we refine
table 1 to paragraphs (c), (g), (i), (j), and (k) of the proposed AD to
further identify part numbers by specifying the part number, and then
use parenthetical groups in order to segregate the part numbers for the
redesigned seating systems.
We agree because the redesigned seating systems are not affected by
the identified unsafe condition. The redesigned seating systems have
new part numbers. Table 1 to paragraphs (c), (g), (i), (j), and (k) of
the proposed AD was based upon the Zodiac Seats California technical
standard order (TSO) authorization. We have revised table 1 to
paragraphs (c), (g), (i), (j), and (k) of this AD by providing
additional part number details to specify only those seats having the
unsafe condition.
Also, the part number format for model number 4170 in table 1 to
paragraphs (c), (g), (i), (j), and (k) of the proposed AD has been
revised to reflect the current format.

Request To Revise Applicability To Exclude Certain Part Numbers

Bombardier requested that we exclude certain parts from the
applicability of the proposed AD. Bombardier stated that seats that do
not have meal/food trays nor upper literature pockets, such as part
numbers 41763002-( )-( ), 41765002-( )-( ), and 41767002-( )-( ),
should be excluded. Bombardier stated that these seats are either: (1)
Installed at a pitch range of 41 inches to 42 inches or a pitch of 45
inches, making it unlikely that a passenger seated behind this seat
would be susceptible to neck injuries during forward impacts addressed
in the proposed AD; or (2) are the last row in front of a bulkhead, and
thus no passengers would ever impact the last row of seats when
subjected to the forward impacts addressed in the proposed AD.
Bombardier also recommended that the format of ``41XX( )-( )-( )'' be
revised to ``41XXXXXXXX-( )-( ) to specify additional detail.
We partially agree with the commenter's request. The initial
installation controls the seating positions at a defined pitch range.
However, table 1 to paragraphs (c), (g), (i), (j), and (k) of the
proposed AD was established based on the TSO authorization of the
seating systems and addresses both the initial installation and
secondary market in which the seating system may have been modified
after issuance of the type certificate.
Therefore, we have revised paragraph (c) of this AD to exclude part
numbers 41763002-( )-( ), 41765002-( )-( ), and 41767002-( )-( ), but
only if the seats have not been modified to add a food tray or an upper
literature pocket. We also revised the part number format in table 1 to
paragraphs (c), (g), (i), (j), and (k) of this AD to specify additional
detail.

Request To Revise Applicability To Exclude Certain Parts Based on
Installation Instructions

Zodiac Seats California requested that we exclude seats from the
applicability of the proposed AD based on how they were originally
installed. Zodiac Seats California stated that certain seats do not
have the injurious condition cited in the NPRM due to how they were
installed. Zodiac Seats California cited the following examples: Last
row seats that do not have aft-mounted food tables; seats installed at
pitches at 39.5 inches or greater; and seats installed at pitches
greater than 41 inches that do not have aft-mounted food tables on the
forward exit seat. Zodiac Seats California identified multiple part
numbers that should be excluded.
We do not agree. While the Zodiac Seats California ``Instructions
for Installation and Limitations'' provides guidance for the
installation of the seating systems, it is not mandatory that
installers follow the guidance. The seats may be modified in the
secondary market in which seat configurations and airplane interior
installations may occur without Zodiac Seats California's or the
airplane original equipment manufacturer's participation. Therefore, we
cannot exclude seats based on the original installation. In addition,
dynamic 16g head injury criteria (HIC) tests at a seat pitch of 39.5
inches using the FAA 50-percentile Hybrid II Anthropomorphic Test
Device (ATD) may lead to the conclusion that the unsafe condition does
not exist; however, the tests do not evaluate a range of occupants. We
have not changed this AD in this regard.

Request To Revise Applicability To Exclude Seats on The Boeing Company
Model MD-90-30 Airplanes

Zodiac Seats California requested that we revise the applicability
of the proposed AD by excluding model number 4170 seats installed on
The Boeing Company Model MD-90-30 airplanes. Zodiac Seats California
stated that the MD-90-30 installation does not require 16g row-to-row HIC
tests because Model MD-90-30 airplanes are not required to comply with
14 CFR 25.562(c)(5) and (c)(6). Delta Airlines (Delta) requested that
we clarify whether the AD is applicable to Model MD-90-30 airplanes.
We agree to clarify the applicability because seat model number
4170 includes a group of seating systems that share a design feature
that does not provide occupant impact protection. Known installations
include both Model MD-90-30 and Model 717-200 airplanes. Excluding
Model MD-90-30 airplanes would put passengers on those airplanes at
risk for a potential serious injury. In addition, compliance with FAA
standards that are in place at the time of certification (including
Model MD-90-30 certification requirements) does not preclude the
possibility that an unsafe condition will be identified in the future,
which is the case here.
Paragraph (c) of this AD identifies affected seating systems, which
are installed on, but not limited to, the airplanes identified in
paragraphs (c)(1) through (c)(9) of this AD. Although Model MD-90-30
airplanes with affected seating systems are included in the
applicability of this AD as a result of the phrase ``but not limited
to,'' we have added this model to paragraph (c)(1) of this AD for
clarification. The phrase ``but not limited to'' also covers any other
aircraft that these seats may have been installed on via the secondary
market, such as seats that have been excessed from one air carrier and
put onto another airplane not identified in this AD via a supplemental
type certificate or other installation approval method. These seating
systems may cause serious injury to passengers during forward impacts
when subjected to certain inertia forces; therefore, these seating
systems are subject to the requirements of this AD.

Request To Revise Applicability To Include Components of Seating
Systems

United Parcel Service (UPS) requested that we revise the
applicability of the proposed AD to include airplanes with components
of the affected seating systems installed. UPS stated that the
applicability of the proposed AD affects all airplanes equipped with
the seating systems identified in paragraph (c) of the proposed AD. UPS
added that paragraph (k) of the proposed AD has requirements that
affect additional airplanes, and proposed that the applicability should
specify all airplanes that may have components of the subject seat
systems installed. Delta stated that the language in paragraph (k) of
the proposed AD places an excessive burden on operators that may use
components as spares on other seating systems.
We do not agree to change the applicability of this AD in this
regard. However, we do agree to clarify the intent of paragraph (k) of
this AD. Paragraph (k) only applies to airplanes affected by the
applicability specified in paragraph (c) of this AD, i.e., airplanes on
which affected seating systems are installed. Paragraph (k) of this AD
does not prohibit installing components on airplanes that have seating
systems that are not included in the applicability specified in
paragraph (c) of this AD. We have not changed this AD in this regard.

Request To Revise Applicability to Exclude Seat Systems Having Part
Number 4157x003-( )-( )

Embraer requested that we revise the applicability to exclude part
number 4157x003-( )-( ). Embraer stated that part is no longer affected
by the unsafe condition identified in the NPRM.
We agree that part number 4157x003-( )-( ) is not affected by the
identified unsafe condition. As stated previously, we have revised
table 1 to paragraphs (c), (g), (i), (j), and (k) of this AD to clearly
identify affected parts; that table does not include part number
4157x003-( )-( ).

Request To Delay Issuance of the Proposed AD

Austrian Airlines AG (which consists of Air Dolomiti, Austrian
Airlines, and Lufthansa CityLine) stated that no technical option (such
as a technical modification from Zodiac Seats California) is included
in the proposed AD to keep the system on the airplane after the 60-
month time limit for eliminating the unsafe condition.
We infer the commenter is requesting that we delay the proposed AD
until a modification of affected seating systems is available. We do
not agree with the commenter's request. We have determined that an
unsafe condition exists and that the requirements in this AD are needed
to address that unsafe condition. However, under the provisions of
paragraph (l) of this AD, we will consider requests for approval of a
modification of the seating system if sufficient data are submitted to
substantiate that the modification would provide an acceptable level of
safety. We have not changed this AD in this regard.

Request To Allow an Alternative Method of Compliance

Zodiac Seats California, SkyWest Airlines, and Delta requested that
we allow modification of the seats via a Zodiac service bulletin.
Skywest stated that paragraph (g) of the proposed AD only allows for
the removal of the seats. Skywest stated that if the request cannot be
added to the proposed AD, alternative methods of compliance (AMOCs)
will be requested to be able to use service bulletins to modify the
seats. Delta stated that Zodiac is developing a seating system design
that removes the unsafe condition by modifying the seats. Zodiac Seats
California proposed to add the implementation of eight service
bulletins as a solution to the proposed AD requirements. Zodiac Seats
California stated it has been working with the FAA's Los Angeles ACO to
identify a solution that can be implemented on in-service seats.
We acknowledge the work that Zodiac Seats California has done to
address the identified unsafe condition on the affected seating
systems. However, Zodiac Seats California has not developed design
solutions to correct the unsafe condition for each of the seating
systems (all relevant service bulletins have not been issued). Once all
the service bulletins have been issued, we can determine if they
adequately address the identified unsafe condition. We do not consider
that delaying this action until after the release of the manufacturer's
planned service information is warranted, since the actions required by
this AD adequately address the unsafe condition. However, under the
provisions of paragraph (l) of this AD, we will consider requests for
approval of an AMOC if sufficient data are submitted to substantiate
that the change would provide an acceptable level of safety. We have
not changed this AD in this regard.

Request To Extend Compliance Time

Austrian Airlines AG requested that we allow more time for
compliance. The commenter stated that additional time for compliance is
needed so that suitable alternative seating systems could be procured
and installed (i.e., time is needed for research and certification).
We do not agree to extend the compliance time in this AD. Operators
must comply with the actions in this AD within the compliance times
specified in this AD in order to address the identified unsafe
condition. The compliance times in this AD are based on the relative
risk to safety resulting from non-compliance with 14 CFR
25.785 and the identified unsafe condition. However, under the
provisions of paragraph (l) of this AD, we will consider requests for
approval of an extension of the compliance time if sufficient data are
submitted to substantiate that the new compliance time would provide an
acceptable level of safety.

Request To Clarify the Determination of the Unsafe Condition for
Previously Certified Seats

Austrian Airlines AG stated that the proposed AD does not mention
why the Model 4157( )-( )-( ) seats were certified on Bombardier Inc.
Model ``CRJ 900 airplanes'' and Embraer S.A. Model ERJ 190 airplanes
about five years ago, but now do not fulfill FAA seat certification
requirements.
Zodiac Seats California stated that since the seats identified in
table 1 to paragraphs (c), (g), (i), (j), and (k) of the proposed AD
were certified prior to the FAA accepting ``Nij < 1'' as a proposed
means of evaluating neck injury, those seats should not be subject to
an AD. Zodiac Seats California noted that when the regulations for HIC
and spine loads were introduced, seats certified prior to that time
were not required to be removed or modified.
We infer the commenters are requesting that we clarify our
determination of the unsafe condition on previously certificated seats.
We agree to provide clarification. As part of seat certification
requirements (14 CFR 21.605(a)(3), amendment 21-67, and 14 CFR
21.603(a)(1), amendment 21-92), an applicant makes a statement of
conformance certifying that they have met the requirements of the
applicable regulations and that the article concerned meets the
applicable TSO that is effective on the date the application is made.
Complying with FAA standards that are in place at the time of
certification does not preclude the possibility that an unsafe
condition will be identified in the future, which is the case here.
Therefore, we have not revised this AD in this regard.
Regarding the use of ``Nij < 1 '' for evaluating neck injuries, the
method was originally proposed by Zodiac Seats California in 2015 to
define the limits of the unsafe condition, and the method was accepted
by the FAA. In 2016, the Industry Ad Hoc Committee asked for and
received clarification from the FAA on this method. 49 CFR 571.208
currently defines a criterion for neck tension and compression, as well
as a criterion that combines the effect of the neck-bending moment and
axial force, called Nij.

Request To Revise Unsafe Condition Language

The Industry Ad Hoc Committee and Zodiac Seats California requested
that we revise the language for the unsafe condition in the proposed
AD. The commenters stated that the focus should be on the injury
mechanism that both industry and FAA find to be unacceptable (direct
neck contact), and that we should delete the description of head motion
and excessive neck loading. The commenters stated the Zodiac Seats
California data do not support statements in the NPRM that refer to
unimpeded sliding motion down the back of the seat occurring during
testing. The commenters noted that the seats were certified according
to certain regulations and, after a later review, the FAA determined
that the interaction between the neck/chin and tray table was not
acceptable. The commenters agreed that direct neck interaction and soft
tissue contact is not acceptable. However, the commenters stated that
Zodiac Seats California has been working to redesign and recertify some
of the seat models.
The commenters also expressed disagreement that to show compliance
with 14 CFR 25.785, the ATD must demonstrate an unimpeded sliding
motion down the back of the seat. The commenters stated that a review
of the ATD head motion during a dynamic test is subjective and
inaccurate, and there is no established level of performance defined in
14 CFR 25.785 or in any other part 25 regulation with regard to sliding
head motion or neck injury. The Industry Ad Hoc Committee referred to a
Zodiac Seats California report that does not corroborate the statements
specified in the proposed AD.
The Industry Ad Hoc Committee and Zodiac Seats California stated
that the associated criterion establishing proper evaluation to prevent
a serious injury provided by the FAA is incomplete for validating
airplane interior performance and practically impossible to duplicate.
The Industry Ad Hoc Committee and Zodiac Seats California noted that
the FAA is still actively developing and clarifying both the measuring
techniques and requirements to support the NPRM. The Industry Ad Hoc
Committee and Zodiac Seats California stated the rationale for the NPRM
creates an inconsistent interpretation of 14 CFR 25.785 when it
includes requiring an unimpeded sliding motion of the head and neck
bending without verifying this condition does not exist across other
seat designs. The Industry Ad Hoc Committee and Zodiac Seats California
also asked how an applicant is expected to ensure compliance to 14 CFR
25.785 using guidance published in Advisory Circular (AC) 25-17A
(``Transport Airplane Cabin Interiors Crashworthiness Handbook''), May
18, 2009, for all other areas on the seat within potential head strike
range not specifically impacted during a 14 CFR 25.562 test event.
We do not agree with the request to revise the unsafe condition
language. However, we will further explain our assessment. The FAA and
Ag[ecirc]ncia Nacional de Avia[ccedil][atilde]o Civil (ANAC) (Brazil)
reviewed seven videos from the technical standard order authorization
for TSO-C127a seating systems. Based on the video, the FAA
characterized the interaction of the ATD chin and the tray table into
five cases: two that are normal (typical) interactions, and three that
are not. In the two typical interactions, the head either slides down
the seat back and tray table unimpeded, or the head crushes the tray
table inward and dislodges it downward. The FAA and Zodiac Seats
California agreed that two of the abnormal cases are unsafe and
corrective action is required.
The remaining interaction involves a scenario where the bottom of
the chin (the area closest to the face) catches the top of the tray
table, dislodging the table downward as the head slides down the seat
back. This condition, which was limited to seating systems with the
marketing identification of Slim Plus, needed further investigation. On
June 2, 2015, Zodiac Seats California proposed the pass/fail criteria
for the investigation of those seating systems in which one or both ATD
exhibited this interaction. In August 2015, the FAA witnessed testing
of three seating systems at the Zodiac Seats California facility to
evaluate this interaction. Zodiac Seats California concluded that
design changes to the upper literature pocket and food tray table are
necessary.
This AD does not specify that ATD interaction between the ATD and
seat back must be a sliding motion. The unsafe condition is based upon
the Los Angeles ACO's review of TSO -C127, TSO-C127a, and TSO-C127b
videos from numerous applicants (including, but not limited to, Embraer
Aero Seating Technologies, Recaro, and TIMCO) for seating systems. The
Zodiac Seats California design is such that a new potential injury to
the occupant is introduced with neck/chin interaction. Zodiac Seats
California proposed a method of compliance to quantify the injury for
these seating systems (including the use of Nij), and the FAA found the
methodology to be acceptable. However, compliance with Nij is not being
required by this AD.

Regarding the requests to revise the unsafe condition description,
this information was included in the Discussion section of the NPRM,
which is not restated in this final rule. Therefore, there is no need
to revise this final rule in this regard.

Request To Clarify the Determination of Unsafe Condition

The Industry Ad Hoc Committee and Zodiac Seats California stated
the NPRM was initiated with inconclusive data, creating a non-standard
approach within industry based on a number of unanswered questions. The
commenters requested clarification of how the unsafe condition was
determined. The commenters questioned if the FAA has determined that an
``unimpeded sliding motion'' and/or Nij is the right criteria for
evaluating neck injury in aircraft interiors.
The Industry Ad Hoc Committee and Zodiac Seats California also
stated that evaluation of potential neck injury severity by reviewing
test videos of the Hybrid II ATD head motion along the seat back
surface is inaccurate and subjective. The Industry Ad Hoc Committee and
Zodiac Seats California reiterated that it is not possible to determine
the extent of neck bending loads leading to neck injury by video
evaluation only. The Industry Ad Hoc Committee and Zodiac Seats
California stated that any new regulatory performance criteria defined
by the FAA must be developed through comprehensive research to assess
validity, repeatability, and feasibility. The Industry Ad Hoc Committee
concluded that the FAA should establish appropriate injury criteria
with FAA research data, follow the proper rulemaking process, and
perform a cost benefit analysis of new regulations on type certificate/
supplemental type certificate projects. The Industry Ad Hoc Committee
requested that FAA continue research with the FAA Hybrid III ATD and
fully substantiate Nij pass/fail criteria before establishing a
threshold of Nij < 1 and associated force/moment limits for row-to-row
dynamic impact tests, which forces the industry to a more conservative
value than necessary. The Industry Ad Hoc Committee noted the seat
supplier community has already attempted to clarify and mitigate the
FAA's concerns and has offered a more specific evaluation method.
Delta suggested that further testing and industry discussion should
take place prior to any rulemaking that would allow inclusion of
National Highway Traffic Safety Administration (NHTSA) neck criteria
and potential neck interactions into injury testing requirements to
comply with 14 CFR 25.785.
We agree to clarify our determination of the unsafe condition. No
new criteria have been established by the FAA. However Zodiac Seats
California has proposed, and the FAA accepted, criteria that
substantiated the unsafe condition. The use of Nij has been volunteered
and accepted as one means of demonstrating compliance to 14 CFR 25.785.
The FAA reviewed screen captures when Zodiac Seats California
approached the FAA with a concern of the ATD and seat back interaction.
The FAA advised Zodiac Seats California to revise the design to address
the interaction. We acknowledge that loads and injury cannot be
evaluated by video only and note that Zodiac Seats California proposed
criteria that included neck bending loads to determine whether the FAA
concern about injuries was substantiated. The potential for injury was
quantified and substantiated.
We do not agree that additional research is necessary to establish
the human tolerance for neck injuries. The Nij, as implemented by
NHTSA, was specifically intended to evaluate an injurious combined
tension/extension loading condition that can be created by airbag
interaction or when the ATD chin hangs up on a protruding seat back
feature (e.g., downward sliding is arrested, chin catches, hangs or
impedes with a tray ledge or other seat feature).
Therefore, the FAA finds that when a quantitative assessment is
necessary, the NHTSA Nij and load limit criteria are well-suited to
assessing the injury potential of seat back interactions and airbag/
wall interactions. We have not changed this AD in this regard.

Request To Clarify the Determination of the Injury Criteria and the
Effect on the Regulations

Delta requested that we provide additional details on the relevant
information evaluated for this NPRM. Delta asked that we further define
the testing and findings that were used to determine new injury
mechanisms and neck bending loads that were found to contribute to the
unsafe condition on previously approved seats. Delta also requested
confirmation that the NPRM does not formalize the FAA's position that
new neck injury mechanisms should be included in injury criteria
requirements of 14 CFR 25.785. Delta also requested that we confirm
that the NPRM does not redefine or add requirements to 14 CFR 25.785.
Delta stated that Nij < 1 is not injury criteria under 14 CFR 25.562 or
14 CFR 25.785.
We agree to provide clarification. This AD does not redefine or add
requirements to 14 CFR 25.785. However, new seating system designs are
introducing new serious injury mechanisms that are considered unsafe
conditions. When the new injury mechanisms are observed, it is up to
industry to identify them as injurious even when criteria to define
them may not exist, and to develop safety features that minimize those
injuries or remove the injury mechanisms. This AD does not impose, nor
does it identify, new criteria to quantify such injury mechanisms.
However, if a test method would be proposed to quantify the injury
in an AMOC, we would review the AMOC proposal for corrective action to
these seating systems. The use of Nij and its tension, compression,
flexion, extension, rotation, neck impact, and chin-concentrated
loading is one method of showing the system is not injurious. This AD
does not mandate using particular criteria; however, the use of Nij was
a method proposed by Zodiac Seats California and found acceptable by
the FAA.

Request To Revise the Parts Installation Limitations and Prohibition

Bombardier, Embraer, and Zodiac Seats California requested that we
delay the implementation of paragraph (i) of the proposed AD, ``Parts
Installation Limitations: Seating Systems.'' Embraer also requested
that we delay the implementation of paragraph (k) of the proposed AD,
``Parts Installation Prohibition: Components of Seating Systems.''
Bombardier requested that we change ``As of the effective date of this
AD, no person may install . . .'' in paragraph (i) of the proposed AD
to a date that would be approximately six months after the effective
date of the AD. Zodiac Seats California requested that we allow
installation of seats, except for part numbers 4157( )-( )-( ) and
4175( )-( )-( ), to be installed for several months after the effective
date of the AD.
Bombardier stated that it currently deliveries Model CRJ900 and
Q400 airplanes that have the affected seats to operators outside of the
United States. Bombardier noted that Transport Canada Civil Aviation
(TCCA) has stated it will adopt the FAA's AD immediately and added that
Zodiac Seats California has not certified alternative seats. Bombardier
stated that since operators will refuse delivery of airplanes without
seats, it requests delaying the effective date of paragraph
(i) of the proposed AD. Bombardier stated that additional time is
necessary to completely assess the situation and provide a suitable
plan in order to not affect future production deliveries.
Embraer requested that we revise paragraph (i) of the proposed AD,
as well as paragraph (k) of the proposed AD, to allow certain defined
part numbers to be installed on newly manufactured aircraft beyond the
effective date. Embraer stated that paragraph (i) of the proposed AD
will effectively stop deliveries of Model ERJ 170 and ERJ 190
airplanes. Embraer stated no other seat replacements are currently
available and, therefore, the proposed AD would affect the delivery of
16 airplanes from Embraer to the United States. Embraer stated that the
proposed change would result in a negligible increase in the number of
seats affected by the proposed AD.
We disagree with the commenters' requests. Zodiac Seats California
has confirmed that affected seats are not being delivered to aircraft
manufacturers and only seats with a new design (i.e., seats that are
not affected by this AD) are being delivered. Therefore, production
delivery of aircraft should not be impacted. Operators that receive
aircraft with the affected seats have the compliance time of 60 months
to comply with this AD.
We have determined that this AD should prohibit installation of the
unsafe parts as of the effective date of this AD, except under certain
conditions, as specified in paragraphs (i)(1) and (i)(2) of this AD. We
have not changed this AD in this regard. However, under the provisions
of paragraph (l) of this AD, we will consider requests for approval of
an extension of the compliance times for parts installations if
sufficient data are submitted to substantiate that the change would
provide an acceptable level of safety.

Request To Revise the Parts Installation Provisions

Skywest Airlines requested that we change the text in the parts
installation provisions of paragraph (j) of the proposed AD from `` . .
. other than those installed as direct spares, . . . '' to `` . . .
other than those installed as direct spares, or on production aircraft,
. . . .'' The commenter stated that paragraphs (i) and (j) of the
proposed AD do not adequately address the installation of affected
seats on newly built airplanes.
We do not agree with the request to allow the installation of known
affected seating systems on production airplanes. The intent of
paragraphs (i) and (j) of this AD is to limit the introduction of known
unsafe parts in the worldwide fleet. Granting the request would
increase the population of seating systems that may cause serious
injury to the occupant during forward impacts when subjected to certain
inertia forces. We have not revised this AD in this regard.

Request To Clarify Prohibition of Components

Two commenters requested that we revise paragraph (k) of the
proposed AD. Delta requested that we revise paragraph (k) of the
proposed AD to prohibit only seat system components that directly
contribute to the unsafe condition identified in the proposed AD. Delta
stated that there are various components, such as cushions, seat
covers, etc., that are not related to the unsafe condition.
UPS stated that the description of ``component'' is too generic.
UPS stated it does not think the intent is to limit the installation of
a certain restraint system, or even a bolt, on all airplanes because
the part was installed on an affected seating system. UPS stated the
proposed AD should identify specific parts that are prohibited from
use.
We agree to clarify the prohibited components. There are items such
as the seat cushions, seat pans, restraint systems, and track fittings
that are not critical components of the injurious mechanism. We have
revised paragraph (k) of this AD by replacing the text ``any
component'' with ``components critical to the unsafe condition
mechanism.'' We have also added a sentence to the introductory text of
paragraph (k) of this AD to specify that components critical to the
unsafe condition mechanism are identified as the seat back assembly,
including food tray assembly, food tray latch, food tray arms,
hydraulic seat lock (hydrolock), and energy absorbing system.

Request To Revise Cost

Multiple commenters (SkyWest Airlines, UBS Equity Research--
Aerospace and Defence, Bombardier, Austrian Airlines AG, Delta, Zodiac
Seats California, and the Industry Ad Hoc Committee) requested that we
clarify or increase the cost estimate. UBS Equity Research--Aerospace
and Defence asked if the cost of seat modification is estimated to be
$85 per seat or whether a replacement is necessary. Multiple commenters
asked that the cost analysis include the costs to procure replacement
seats; several commenters specified research costs, development costs,
engineering certification costs, and the cost of seat replacement. The
commenters also asked us to account for loss of revenue; several
commenters noted that commercial airplanes cannot be operated for their
intended purpose without seats installed. Skywest Airlines noted that
the cost of replacement seats is estimated to be between $250,000 and
$500,000 for the affected seats in one airplane. Bombardier suggested
adding 2 work-hours for procuring and reinstalling alternate certified
seats.
We do not agree to revise the costs specified in this AD. We have
included the estimated cost of the actions required by this AD, which
is applicable to the U.S. fleet. This AD requires removal of non-
compliant seats, and we have included the costs for that action.
Removing non-compliant seats addresses the unsafe condition and
restores compliance to the airworthiness regulations.
While this AD does not require modifying or replacing seats, we
recognize that operators could choose to replace non-compliant seating
systems or modify affected seats. However, we are unable to make a
reasonable assessment of how many seats would be required to be
replaced or to assess the cost of modifying affected seats.
Modifications would need to be approved as an AMOC in accordance the
procedures specified in paragraph (l) of this AD. We also acknowledge
that, for operators that remove non-compliant seats, there could a loss
of revenue.
We also do not consider it appropriate to attribute the costs
associated with airplane ``down time'' to an AD. Normally, compliance
with an AD will not necessitate any additional down time beyond that of
a regularly scheduled maintenance hold. Even if additional down time is
necessary for some airplanes in some cases, we do not have sufficient
information to evaluate the number of airplanes that may be affected or
the amount of additional down time that may be required. Therefore,
attempting to estimate such costs is impractical. We have not revised
this AD in this regard.

Request To Clarify "Vague" Terminology

The Industry Ad Hoc Committee and Zodiac Seats California stated
that the proposed AD used subjective and ``vague'' terms such as
``catch'' and ``unimpeded sliding motion down.'' The Industry Ad Hoc
Committee requested that the FAA work with industry to develop
additional research and avoid these terms. The Industry Ad Hoc
Committee suggested terms such as ``directly impedes the head's
downward sliding motion'' and ``chin hang-up.''
We agree to provide further clarification. Our review of
certification testing has shown that in dynamic seat tests, impact of
an ATD head onto a typical transport passenger seat back normally
results in an initial head strike followed by an unimpeded sliding
motion down the back of the seat. In addition, as stated in the
Discussion section of the NPRM, the design of the affected seating
systems introduced new injury mechanisms, such that the chin can
``catch'' on the seats, causing high neck bending loads and direct
concentrated loading on the neck. We have not changed this AD in this
regard.

Request for Collaborative Research

Boeing recommended an all-inclusive, industry-wide research and
data analysis evaluation to develop a common and measurable standard
with acceptable limitations for any new requirement such as neck injury
criteria. Boeing stated it welcomes a collaborative research approach
with the FAA and industry partners to develop appropriate neck injury
criteria for aircraft seats prior to any rulemaking activity.
We agree that a collaborative research approach is beneficial. As
early as October 2007, during the Fifth Triennial International
Aviation Fire and Cabin Safety Research Conference, industry was
notified of the potential for seat back interaction to produce high
neck loads. The data available at that time, however, did not indicate
that neck injury was a significant risk in most of the forward facing
configurations tested.
An example of this specific type of injury was brought to industry
attention during The Seventh Triennial International Fire & Cabin
Safety Research Conference in December 2013. The FAA welcomes
additional research, as appropriate, and the development of appropriate
neck injury criteria for aircraft seats.

Conclusion

We reviewed the relevant data, considered the comments received,
and determined that air safety and the public interest require adopting
this AD with the changes described previously and minor editorial
changes. We have determined that these minor changes:
Are consistent with the intent that was proposed in the
NPRM for correcting the unsafe condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM.
We also determined that these changes will not increase the
economic burden on any operator or increase the scope of this AD.

Costs of Compliance

We estimate that this AD affects 10,482 seating systems installed
on, but not limited to, various transport category airplanes of U.S.
registry.
We estimate the following costs to comply with this AD:

Estimated Costs

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.
We are 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) Is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979),
(3) Will not affect intrastate aviation in Alaska, and
(4) 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):