DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-0696; Product Identifier 2019-NM-136-AD; Amendment
39-19730; AD 2019-18-03]
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 series airplanes, excluding Model 737-100,
-200, -200C, -300, -400, and -500 series airplanes. This AD requires
revising the existing maintenance or inspection program to remove text
that allows the size of the thrust reverser upper locking actuator lock
sensor target to be changed, and, for certain airplanes, performing
repetitive integrity tests of the thrust reverser upper locking
actuator. This AD was prompted by a report indicating that alteration
of thrust reverser upper locking actuators in accordance with certain
data in the Boeing aircraft maintenance manual (AMM) could delay or
prevent detection of the failure of the locking mechanism of a thrust
reverser upper locking actuator. The FAA is issuing this AD to address
the unsafe condition on these products.

DATES: This AD is effective October 3, 2019.
The FAA must receive comments on this AD by November 4, 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.

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-
0696; 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, 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: Christopher Baker, Aerospace Engineer,
Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des
Moines, WA 98198; phone and fax: 206-231-3552; email:
Christopher.R.Baker@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

In May 2019, Boeing informed the FAA that alteration of thrust
reverser upper locking actuators, in accordance with unapproved data in
the Boeing AMM, could cause a locking mechanism failure of a thrust
reverser upper locking actuator to remain undetected for thousands of
flights.
Boeing informed the FAA of the risk that operators could use an
existing AMM procedure that was intended for use in rigging a newly
installed thrust reverser upper locking actuator to instead alter the
functioning of a worn upper locking actuator's lock indication. That
procedure removes material from the upper locking actuator's lock
sensor target until the upper locking actuator's unlocked indication
(the ``REVERSER'' light on the flight deck aft overhead panel, which is
illuminated when the upper locking actuator is unlocked or when other
system failures are detected) is no longer illuminated. However, that
procedure does not require a check to verify that the thrust reverser
upper locking actuator locking mechanism is operative or that the
unlocked indication functions normally after removal of the material.
As a result, it is possible that use of this procedure could prevent
actuator unlocked indications to the flight crew if the thrust reverser
upper locking actuator locking mechanism has already failed or
subsequently fails.
An undetected unlocked thrust reverser upper locking actuator in
flight significantly increases the likelihood of an in-flight
deployment of the thrust reverser. In-flight thrust reverser deployment
in some phases of flight would likely result in loss of airplane
control.

FAA's Determination

The FAA is issuing 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.

AD Requirements

This AD requires revising the existing maintenance or inspection
program to remove certain text from all locations in the existing
maintenance and inspection program that instructs the maintainers to
remove material from or grind or trim the sensor target of the thrust
reverser upper locking actuator. For Model 737-600, -700, -700C, -800,
-900, and -900ER series (737 NG) airplanes, this AD also requires
repetitive integrity tests of the thrust reverser upper locking
actuator.
The Model 737-8 and -9 (737 MAX) airplane fleet is a young fleet
and those airplanes have not been subjected to enough wear to warrant
the use by any operator of the sensor target trimming procedure that
leads to the upper locking actuator lock indication failure that may
exist on 737 NG airplanes. The FAA therefore has determined that the
integrity test is not necessary for the 737 MAX fleet.

Interim Action

The FAA considers this AD interim action. The manufacturer is
currently developing a modification that will address the unsafe
condition identified in this AD. Once this modification is developed,
approved, and available, the

FAA might consider additional rulemaking.

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.) 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 seeking comment prior to the
rulemaking. Similarly, 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 alteration of thrust reverser upper locking actuators in
accordance with certain unapproved AMM data could cause a thrust
reverser upper locking actuator that is unlocked in flight to remain
undetected, which could significantly increase the likelihood of an in-
flight deployment of the thrust reverser and consequent loss of
airplane control. The compliance time for the required action is
shorter than the time necessary for the public to comment and for
publication of the final rule.
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, for the reasons stated above, 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.

Comments Invited

This AD is a final rule that involves requirements affecting flight
safety and was not preceded by notice and an opportunity for public
comment. However, the FAA invites you to send any written data, views,
or arguments about this final rule. Send your comments to an address
listed under the ADDRESSES section. Include the docket number FAA-2019-
0696 and Product Identifier 2019-NM-136-AD at the beginning of your
comments. The FAA specifically invites comments on the overall
regulatory, economic, environmental, and energy aspects of this final
rule. 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
http://www.regulations.gov, including any personal information you
provide. The FAA 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
Christopher Baker, Aerospace Engineer, Propulsion Section, FAA, Seattle
ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax:
206-231-3552; email: Christopher.R.Baker@faa.gov. Any commentary that
the FAA receives which 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 2,149 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:

Estimated Costs

The FAA has determined that revising the existing maintenance or
inspection program takes an average of 90 work-hours per operator,
although the agency recognizes that this number may vary from operator
to operator. In the past, the FAA has estimated that this action takes
1 work-hour per airplane. Since operators incorporate maintenance or
inspection program changes for their affected fleet(s), the FAA has
determined that a per-operator estimate is more accurate than a per-
airplane estimate. Therefore, the FAA estimates the total cost per
operator to be $7,650 (90 work-hours x $85 per work-hour).
The FAA estimates the following costs to do any necessary
replacement that would be required based on the results of the
integrity test. The FAA has no way of determining the number of
aircraft that might need this replacement:

On-Condition Costs

According to the manufacturer, some or all of the costs of this AD
may be covered under warranty, thereby reducing the cost impact on
affected individuals. The FAA does not control warranty coverage for
affected individuals. As a result, the FAA has included all known costs
in the cost estimate.

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 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

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

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):