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PROPOSED AD THE BOEING COMPANY: Docket No. FAA-2019-0478; Product Identifier 2019-NM-040-AD.
(a) COMMENTS DUE DATE

    The FAA must receive comments on this AD action by August 22, 2019.

(b) AFFECTED ADS

    This AD replaces AD 2017-12-07, Amendment 39-18922 (82 FR 27416,  June
    15, 2017).

(c) APPLICABILITY

    This AD applies  to all The  Boeing Company  Model  737-800, -900, and
    -900ER series airplanes, certificated in any category.

(d) SUBJECT

    Air Transport Association (ATA) of America Code 21, Air conditioning.

(e) UNSAFE CONDITION

    This  AD was  prompted by  reports of  in-flight failure  of the  left
    temperature control valve and control cabin trim air modulating valve.
    The  FAA is  issuing this  AD to  address the  possible occurrence  of
    temperatures in excess of 100 degrees Fahrenheit in the flight deck or
    the passenger cabin during cruise, which could lead to the  impairment
    of the flightcrew and prevent continued safe flight and landing.

(f) COMPLIANCE

    Comply  with this  AD within  the compliance  times specified,  unless
    already done.

(g) RETAINED VALVE REPLACEMENT, WITH REVISED COMPLIANCE LANGUAGE

    This paragraph restates the requirements  of paragraph (g) of AD  2017
    -12-07 with revised compliance  language. For airplanes identified  in
    Boeing Alert Service Bulletin 737-21A1203, dated June 8, 2016:  Within
    60 months after July 20,  2017 (the effective date of  AD 2017-12-07),
    replace the left temperature control valve and control cabin trim  air
    modulating valve, as applicable, in accordance with the Accomplishment
    Instructions of Boeing Alert Service Bulletin 737-21A1203, dated  June
    8, 2016.

(h) NEW VALVE IDENTIFICATION AND REPLACEMENT

    For  airplanes not  identified in  paragraph (g)  of this  AD with  an
    original   certificate  of   airworthiness  or   an  original   export
    certificate of airworthiness dated on or before the effective date  of
    this AD, do the actions  specified in paragraphs (h)(1) and  (h)(2) of
    this AD.

(1) Within 60  months  after  the  effective  date of  this AD,  perform a
    general visual inspection  of the left  temperature control valve  and
    control cabin trim  air modulating valve  to determine the  valve part
    numbers. A  review of  airplane maintenance  records is  acceptable in
    lieu of  this inspection  if the  part numbers  of the  valves can  be
    conclusively determined from that review.

(2) If the left temperature control valve or control cabin trim air modul-
    ating  valve has  part number  398908-4: Within  60 months  after  the
    effective date of this AD, replace the left temperature control  valve
    or control  cabin trim  air modulating  valve in  accordance with  the
    Accomplishment  Instructions  of  Boeing  Alert  Service  Bulletin 737
    -21A1203, dated June 8, 2016.

(i) PARTS INSTALLATION PROHIBITION

    As of the  effective date of  this AD, no  person may install  a valve
    having part number  398908-4, in either  the left temperature  control
    valve location or the control cabin trim air modulating valve location
    on any airplane.

(j) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)

(1) The  Manager, Seattle  ACO Branch,  FAA, has  the authority to approve
    AMOCs for this AD, if requested  using the procedures found in 14  CFR
    39.19. In  accordance with  14 CFR  39.19, send  your request  to your
    principal  inspector or  local Flight  Standards  District  Office, as
    appropriate. If  sending information  directly to  the manager  of the
    certification  office,  send  it  to  the  attention  of  the   person
    identified in paragraph (k)(1) of this AD. Information may be  emailed
    to: 9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.

(2) Before using  any  approved  AMOC, notify  your appropriate  principal
    inspector, or lacking a principal inspector, the manager of the  local
    flight standards district office/certificate holding  district office.

(3) An AMOC that  provides an acceptable level  of safety may be  used for
    any repair, modification, or alteration  required by this AD if  it is
    approved by The Boeing Company Organization Designation  Authorization
    (ODA) that  has been  authorized by  the Manager,  Seattle ACO Branch,
    FAA,  to  make those  findings.  To be  approved,  the repair  method,
    modification  deviation,  or   alteration  deviation  must   meet  the
    certification  basis   of  the   airplane,  and   the  approval   must
    specifically refer to this AD.

(4) For  service  information  that  contains steps  that  are  labeled as
    Required for Compliance (RC),  the provisions of paragraphs  (j)(4)(i)
    and (j)(4)(ii) of this AD apply.

(i) The steps labeled as RC,  including substeps under an RC step  and any
    figures identified in an RC step, must be done to comply with the  AD.
    If a step or substep is labeled "RC Exempt," then the RC requirement
    is removed  from that  step or  substep. An  AMOC is  required for any
    deviations to RC steps, including substeps and identified figures.

(ii) Steps not labeled as RC  may be deviated from using accepted  methods
     in accordance with the  operator's maintenance or inspection  program
     without  obtaining  approval  of  an  AMOC,  provided  the  RC steps,
     including  substeps  and identified  figures,  can still  be  done as
     specified,  and  the  airplane  can  be  put  back  in  an  airworthy
     condition.

(k) RELATED INFORMATION

(1) For  more information  about this  AD, contact  Julie Moon,  Aerospace
    Engineer, Cabin Safety and Environmental Systems Section, FAA, Seattle
    ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax:
    206-231-3571; email: julie.moon@faa.gov.

(2) For service information identified in this AD, contact  Boeing Commer-
    cial Airplanes,  Attention: Contractual  & Data  Services (C&DS), 2600
    Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740- 5600;  telephone
    562-797-1717;  internet  https://www.myboeingfleet.com.  You  may view
    this referenced  service information  at the  FAA, Transport Standards
    Branch, 2200 South 216th St.,  Des Moines, WA. For information  on the
    availability of this material at the FAA, call 206-231-3195.

Issued in Des Moines, Washington, on June 24, 2019. Dionne Palermo, Acting
Director, System Oversight Division, Aircraft Certification Service.

DATES: The FAA  must receive comments  on this proposed  AD by August  22,
2019.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration


14 CFR Part 39

[Docket No. FAA-2019-0478; Product Identifier 2019-NM-040-AD]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD)
2017-12-07, which applies to certain The Boeing Company Model 737-800,
-900, and -900ER series airplanes. AD 2017-12-07 requires replacing the
affected left temperature control valve and control cabin trim air
modulating valve. Since the FAA issued AD 2017-12-07, the agency
determined that the affected parts may be installed on airplanes
outside the original applicability of AD 2017-12-07. This proposed AD
would retain the requirements of AD 2017-12-07, expand the
applicability to include those other airplanes, and add a new
requirement for certain airplanes to identify and replace the affected
parts. 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 August 22, 2019.

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 http://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 above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this NPRM, contact Boeing
Commercial Airplanes, Attention: Contractual & Data Services (C&DS),
2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600;
telephone 562-797-1717; internet https://www.myboeingfleet.com. You may
view this service information at the FAA, Transport Standards Branch,
2200 South 216th St., Des Moines, WA. For information on the
availability of this material at the FAA, call 206-231-3195. It is also
available on the internet at http://www.regulations.gov by searching
for and locating Docket No. FAA-2019-0478.

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-2019-
0478; 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 regulatory evaluation, any comments received, and other
information. The street address for Docket Operations is listed above.
Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Julie Moon, Aerospace Engineer, Cabin
Safety and Environmental Systems Section, FAA, Seattle ACO Branch, 2200
South 216th St., Des Moines, WA 98198; phone and fax: 206-231-3571;
email: julie.moon@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 the ADDRESSES section. Include "Docket No. FAA-2019-0478;
Product Identifier 2019-NM-040-AD" at the beginning of your comments.
The agency specifically invites comments on the overall regulatory,
economic, environmental, and energy aspects of this NPRM. The agency
will consider all comments received by the closing date and may amend
this NPRM because of those comments.

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

Discussion


The FAA issued AD 2017-12-07, Amendment 39-18922 (82 FR 27416, June
15, 2017) ("AD 2017-12-07"), for certain The Boeing Company Model
737-800, -900, and -900ER series airplanes. AD 2017-12-07 requires
replacing the affected left temperature control valve and control cabin
trim air modulating valve. AD 2017-12-07 resulted from reports of in-
flight failure of the left temperature control valve and control cabin
trim air modulating valve. The FAA issued AD 2017-12-07 to address the
possible occurrence of temperatures in excess of 100 degrees Fahrenheit
in the flight deck or the passenger cabin during cruise, which could
lead to the impairment of the flightcrew and prevent continued safe
flight and landing.

Actions Since AD 2017-12-07 Was Issued


Since AD 2017-12-07 was issued, it has been determined that the
affected parts may be installed as rotable spares on airplanes outside
of the applicability of AD 2017-12-07, thereby subjecting those
airplanes to the unsafe condition.

Related Service Information Under 1 CFR Part 51


This proposed AD would require Boeing Alert Service Bulletin 737-
21A1203, dated June 8, 2016, which the Director of the Federal Register
approved for incorporation by reference as of July 20, 2017 (82 FR
27416, June 15, 2017). 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.

FAA's Determination


The FAA is proposing this AD because the agency evaluated all the
relevant information and determined the unsafe condition described
previously is likely to exist or develop in other products of the same
type design.

Proposed AD Requirements


This proposed AD would retain all requirements of AD 2017-12-07,
and expand the applicability to include all The Boeing Company Model
737-800, -900, and -900ER series airplanes. This proposed AD would also
require an inspection or records check to identify the part number of
the affected parts, and for airplanes with affected parts,
accomplishing the actions specified in the service information
described previously, except as discussed under
"Differences Between this Proposed AD and the Service Information."

For information on the procedures and compliance times, see this
service information at http://www.regulations.gov by searching for and
locating Docket No. FAA-2019-0478.

Differences Between This Proposed AD and the Service Information


The effectivity of Boeing Alert Service Bulletin 737-21A1203, dated
June 8, 2016, is limited to certain The Boeing Company Model 737-800,
-900, and -900ER series airplanes. However, the applicability of this
proposed AD includes all The Boeing Company Model 737-800, -900, and
-900ER series airplanes. Because the affected parts are rotable parts,
the FAA has determined that these parts could later be installed on
airplanes that were initially delivered with acceptable parts, thereby
subjecting those airplanes to the unsafe condition. This difference has
been coordinated with Boeing.

Costs of Compliance


The FAA estimates that this proposed AD affects 2,027 airplanes of
U.S. registry. The agency estimates the following costs to comply with
this proposed AD:

Estimated Costs for Required Actions

ACTION
LABOR COST
PARTS COST
COST PER PRODUCT
COST ON U.S. OPERATORS
Inspection/records check (new proposed actions) (Up to 1,708 airplanes). 1 work-hour x $85per hour = $85. $0 $85 Up to $145,180.
Replacement (retained actions from AD 2017-12-07) (Up to 319 airplanes). 9 work-hours x $85 per hour = $765. 4,800 5,565 Up to $1,775,235.

The agency estimates the following costs to do any necessary
replacements that would be required based on the results of the
proposed inspection or records check. The agency has no way of
determining the number of aircraft that might need these replacements:

On-Condition Costs

ACTION
LABOR COST
PARTS COST
COST PERPRODUCT
Replacement................................... 9 work-hours x $85 per hour = $765. $4,800 $5,565

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.

This proposed AD is issued in accordance with authority delegated
by the Executive Director, Aircraft Certification Service, as
authorized by FAA Order 8000.51C. In accordance with that order,
issuance of ADs is normally a function of the Compliance and
Airworthiness Division, but during this transition period, the
Executive Director has delegated the authority to issue ADs applicable
to transport category airplanes and associated appliances to the
Director of the System Oversight Division.

Regulatory Findings


The FAA has 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 above, I certify that the proposed regulation:

(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 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 removing Airworthiness Directive (AD)
2017-12-07, Amendment 39-18922 (82 FR 27416, June 15, 2017), and adding
the following new AD: