AD 2021-08-14

[Federal Register Volume 86, Number 94 (Tuesday, May 18, 2021)]
[Rules and Regulations]
[Pages 26826-26829]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2021-10562]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0270; Project Identifier AD-2021-00352-T; 
Amendment 39-21508; AD 2021-08-14]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule; request for comments.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all 
The Boeing Company Model 737-300, -400, and -500 series airplanes. This 
AD was prompted by a flap synchro wire failure that may go undetected 
by the autothrottle (A/T) computer. This AD requires repetitive BITE 
(built-in test equipment) tests of the A/T computer to detect a flap 
synchro wire failure, and corrective action if necessary. The FAA is 
issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective June 2, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of June 2, 
2021.
    The FAA must receive comments on this AD by July 2, 2021.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
    <bullet> Federal eRulemaking Portal: Go to <a href="https://www.regulations.gov">https://www.regulations.gov</a>. Follow the instructions for submitting comments.
    <bullet> Fax: 202-493-2251.
    <bullet> 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.
    <bullet> 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 final rule, 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 <a href="https://www.myboeingfleet.com">https://www.myboeingfleet.com</a>. You may 
view this service information at the FAA, Airworthiness Products 
Section, Operational Safety 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 at <a href="https://www.regulations.gov">https://www.regulations.gov</a> 
by searching for and locating Docket No. FAA-2021-0270.

Examining the AD Docket

    You may examine the AD docket at <a href="https://www.regulations.gov">https://www.regulations.gov</a> by 
searching for and locating Docket No. FAA-2021-0270; 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 the 
Docket Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Jeffrey Palmer, Aerospace Engineer, 
Systems and Equipment Section, FAA, Los Angeles ACO Branch, 3960 
Paramount Boulevard, Lakewood, CA 90712-4137; phone: 562-627-5351; 
email: <a href="/cdn-cgi/l/email-protection#f9b39c9f9f8b9c80d7aed7a99895949c8bb99f9898d79e968f"><span class="__cf_email__" data-cfemail="abe1cecdcdd9ced285fc85fbcac7c6ced9ebcdcaca85ccc4dd">[email&#160;protected]</span></a>.

SUPPLEMENTARY INFORMATION:

Background

    The FAA previously issued AD 2000-23-34, Amendment 39-12007 (65 FR 
75595, December 4, 2000) (AD 2000-23-34), which applies to all Boeing 
Model 737-300, -400, and -500 series airplanes, and requires replacing 
the existing A/T computer with a new, improved A/T computer that 
included an asymmetric cruise thrust monitor.
    On January 9, 2021, a Model 737-500 series airplane operated by 
Sriwijaya Air was involved in an accident on a flight from Jakarta, 
Indonesia. There were 62 fatalities. During the ongoing accident 
investigation, Boeing reported that a flap synchro wire failure may go 
undetected by the A/T computer on the affected airplanes. Further 
investigation has revealed that the design update for the A/T computer 
required by AD 2000-23-34 does not properly account for a possible 
latent failure of the flap position sensor, which is one data component 
needed to provide the logic necessary for the asymmetric cruise thrust 
monitor to operate. Failure of the asymmetric cruise thrust monitor to 
engage during a large thrust asymmetry

[[Page 26827]]

event could result in loss of control of the airplane. At this time, 
the preliminary data of the ongoing accident investigation shows that 
it is highly unlikely that the accident resulted from the latent 
failure of the flap synchro wire. However, the FAA has determined that 
the unsafe condition identified in this AD could exist or develop in 
Model 737-300, -400, and -500 series airplanes, and that this AD is 
therefore necessary to address the identified unsafe condition.
    The FAA has confirmed that accomplishment of the applicable BITE 
test in the existing airplane maintenance manual (AMM) detects the flap 
synchro wire failure. This test is currently not required to be 
performed repetitively, leading to a potential latent failure if the 
test is not performed regularly, which will be required by this AD.
    Model 737-100 and -200 series airplanes are not affected by this AD 
due to an A/T design difference that is not subject to the identified 
unsafe condition.

FAA's Determination

    The FAA is issuing this AD because the agency has determined the 
unsafe condition described previously is likely to exist or develop in 
other products of the same type design.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Multi-Operator Message MOM-MOM-21-0145-
01B(R2), dated March 30, 2021. This service information specifies 
procedures for performing an A/T computer BITE test, ``A/T BITE TEST 
LRU INTERFACE,'' and corrective actions to repair defects. 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.

AD Requirements

    This AD requires accomplishing the actions specified in the service 
information already described, except as discussed under ``Differences 
Between this AD and the Service Information.''

Differences Between This AD and the Service Information

    Boeing Multi-Operator Message MOM-MOM-21-0145-01B(R2), dated March 
30, 2021, specifies a compliance time of 250 flight hours for the 
initial BITE test. However, this AD requires the initial BITE test 
within 250 flight hours or 2 months after the effective date of this 
AD, whichever occurs first, to ensure that airplanes with low 
utilization rates are addressed in a timely manner.

Interim Action

    The FAA considers this AD to be an interim action. If final action 
is later identified, the FAA might consider further rulemaking then.

Justification for Immediate Adoption and Determination of the Effective 
Date

    Section 553(b)(3)(B) of the Administrative Procedure Act (APA) (5 
U.S.C. 551 et seq.) authorizes agencies to dispense with notice and 
comment procedures for rules when the agency, for ``good cause,'' finds 
that those procedures are ``impracticable, unnecessary, or contrary to 
the public interest.'' Under this section, an agency, upon finding good 
cause, may issue a final rule without providing notice and seeking 
comment prior to issuance. Further, section 553(d) of the APA 
authorizes agencies to make rules effective in less than thirty days, 
upon a finding of good cause.
    An unsafe condition exists that requires the immediate adoption of 
this AD without providing an opportunity for public comments prior to 
adoption. The FAA has found that the risk to the flying public 
justifies forgoing notice and comment prior to adoption of this rule 
because failure of the asymmetric cruise thrust monitor to engage 
during a large thrust asymmetry event could result in loss of control 
of the airplane. Accordingly, notice and opportunity for prior public 
comment are impracticable and contrary to the public interest pursuant 
to 5 U.S.C. 553(b)(3)(B).
    In addition, the FAA finds that good cause exists pursuant to 5 
U.S.C. 553(d) for making this amendment effective in less than 30 days, 
for the same reasons the FAA found good cause to forgo notice and 
comment.

Comments Invited

    The FAA invites you to send any written data, views, or arguments 
about this final rule. Send your comments to an address listed under 
ADDRESSES. Include ``Docket No. FAA-2021-0270 and Project Identifier 
AD-2021-00352-T'' at the beginning of your comments. The most helpful 
comments reference a specific portion of the final rule, 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 final rule 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 
<a href="https://www.regulations.gov">https://www.regulations.gov</a>, including any personal information you 
provide. The agency will also post a report summarizing each 
substantive verbal contact received about this final rule.

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 AD 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 AD, 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 AD. Submissions containing CBI should be sent to Jeffrey 
Palmer, Aerospace Engineer, Systems and Equipment Section, FAA, Los 
Angeles ACO Branch, 3960 Paramount Boulevard, Lakewood, CA 90712-4137; 
phone: 562-627-5351; email: <a href="/cdn-cgi/l/email-protection#b6fcd3d0d0c4d3cf98e198e6d7dadbd3c4f6d0d7d798d1d9c0"><span class="__cf_email__" data-cfemail="115b7477776374683f463f41707d7c7463517770703f767e67">[email&#160;protected]</span></a>. Any commentary 
that the FAA receives that is not specifically designated as CBI will 
be placed in the public docket for this rulemaking.

Regulatory Flexibility Act

    The requirements of the Regulatory Flexibility Act (RFA) do not 
apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt 
a rule without prior notice and comment. Because the FAA has determined 
that it has good cause to adopt this rule without notice and comment, 
RFA analysis is not required.

Costs of Compliance

    The FAA estimates that this AD affects 143 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

[[Page 26828]]



                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
             Action                     Labor cost          Parts cost     Cost per product        operators
----------------------------------------------------------------------------------------------------------------
BITE test......................  1 work-hour x $85 per                $0  $85 per test......  $11,220 per test.
                                  hour = $85 per test.
----------------------------------------------------------------------------------------------------------------

    The FAA has received no definitive data on which to base the cost 
estimates for the on-condition corrective actions specified in this AD.

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, and
    (2) Will not affect intrastate aviation in Alaska.

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

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2021-08-14 The Boeing Company: Amendment 39-21508; Docket No. FAA-
2021-0270; Project Identifier AD-2021-00352-T.

(a) Effective Date

    This airworthiness directive (AD) is effective June 2, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to all The Boeing Company Model 737-300, -400, 
and -500 series airplanes, certificated in any category.

(d) Subject

    Air Transport Association (ATA) of America Code 22, Auto flight.

(e) Unsafe Condition

    This AD was prompted by a flap synchro wire failure that may go 
undetected by the autothrottle (A/T) computer. The FAA is issuing 
this AD to address failure of the flap position sensor, which could 
result in failure of the asymmetric cruise thrust monitor to engage 
during a large thrust asymmetry event, and loss of control of the 
airplane.

(f) Compliance

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

(g) BITE Test

    Within 250 flight hours or 2 months after the effective date of 
this AD, whichever occurs first: Perform the applicable A/T computer 
BITE (built-in test equipment) test, ``A/T BITE TEST LRU 
INTERFACE,'' and before further flight do all applicable corrective 
actions, in accordance with paragraphs 1. through 5. of Boeing 
Multi-Operator Message MOM-MOM-21-0145-01B(R2), dated March 30, 
2021, except as provided in paragraph (h) of this AD. Repeat the 
test thereafter at intervals not to exceed 2,000 flight hours.

(h) Clarification of Service Information Specifications

    Although paragraph 1. of Boeing Multi-Operator Message MOM-MOM-
21-0145-01B(R2), dated March 30, 2021, specifies to prepare the 
airplane for BITE testing ``using the reference/A/, AMM 22-04-00 or 
22-04-10, paragraph 3 and 4 as necessary,'' this AD does not require 
using that service information to accomplish those steps, but 
operators may refer to that information for guidance on the 
procedures.

(i) Reporting

    Although Boeing Multi-Operator Message MOM-MOM-21-0145-01B(R2), 
dated March 30, 2021, specifies to report test results, this AD does 
not require any report.

(j) Credit for Previous Actions

    This paragraph provides credit for the actions specified in 
paragraph (g) of this AD, if those actions were performed before the 
effective date of this AD using Boeing Multi-Operator Message MOM-
MOM-21-0145-01B(R1), dated March 23, 2021.

(k) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Los Angeles 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 responsible Flight Standards 
Office, as appropriate. If sending information directly to the 
manager of the certification office, send it to the attention of the 
person identified in Related Information. Information may be emailed 
to <a href="/cdn-cgi/l/email-protection#5b62761a151676171a1a1814761a16141876093e2a2e3e282f281b3d3a3a753c342d"><span class="__cf_email__" data-cfemail="1f26325e515232535e5e5c50325e52505c324d7a6e6a7a6c6b6c5f797e7e31787069">[email&#160;protected]</span></a>.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the responsible Flight Standards Office.

(l) Related Information

    (1) For more information about this AD, contact Jeffrey Palmer, 
Aerospace Engineer, Systems and Equipment Section, FAA, Los Angeles 
ACO Branch, 3960 Paramount Boulevard, Lakewood, CA 90712-4137; 
phone: 562-627-5351; email: <a href="/cdn-cgi/l/email-protection#ca80afacacb8afb3e49de49aaba6a7afb88aacababe4ada5bc"><span class="__cf_email__" data-cfemail="e1ab848787938498cfb6cfb1808d8c8493a1878080cf868e97">[email&#160;protected]</span></a>.
    (2) Service information identified in this AD that is not 
incorporated by reference is available at the addresses specified in 
paragraphs (m)(3) and (4) of this AD.

(m) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference (IBR) of the service information listed 
in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this service information as applicable to do 
the actions required by this AD, unless the AD specifies otherwise.
    (i) Boeing Multi-Operator Message MOM-MOM-21-0145-01B(R2), dated 
March 30, 2021.
    (ii) [Reserved]
    (3) For service information identified in this AD, contact 
Boeing Commercial

[[Page 26829]]

Airplanes, Attention: Contractual & Data Services (C&DS), 2600 
Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600; telephone 
562-797-1717; internet <a href="https://www.myboeingfleet.com">https://www.myboeingfleet.com</a>.
    (4) You may view this service information at the FAA, 
Airworthiness Products Section, Operational Safety Branch, 2200 
South 216th St., Des Moines, WA. For information on the availability 
of this material at the FAA, call 206-231-3195.
    (5) You may view this service information that is incorporated 
by reference at the National Archives and Records Administration 
(NARA). For information on the availability of this material at 
NARA, email <a href="/cdn-cgi/l/email-protection#3a5c5f5e485f5d14565f5d5b567a545b485b145d554c"><span class="__cf_email__" data-cfemail="0a6c6f6e786f6d24666f6d6b664a646b786b246d657c">[email&#160;protected]</span></a>, or go to <a href="https://www.archives.gov/federal-register/cfr/ibr-locations.html">https://www.archives.gov/federal-register/cfr/ibr-locations.html</a>.

    Issued on April 7, 2021.
Ross Landes,
Deputy Director for Regulatory Operations, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2021-10562 Filed 5-14-21; 4:15 pm]
BILLING CODE 4910-13-P