DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-1071; Product Identifier 2019-NM-165-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 adopt a new airworthiness directive (AD)
for all The Boeing Company Model 737-900ER series airplanes. This
proposed AD was prompted by reports of significant corrosion of
electrical connectors located in the main landing gear (MLG) wheel
well. This proposed AD would require repetitive records checks to
determine exposure to certain deicing fluids or repetitive inspections
for corrosion of the electrical connectors, and corrective actions if
necessary. 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 February
24, 2020.

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 https://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 https://www.regulations.gov by searching
for and locating Docket No. FAA-2019-1071.

Examining the AD Docket

You may examine the AD docket on the internet at https://www.regulations.
gov by searching for and locating Docket No. FAA-2019-1071;
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: Julio C. Alvarez, Aerospace Engineer,
Systems and Equipment Section, FAA, Seattle ACO Branch, 2200 South
216th St., Des Moines, WA 98198; phone and fax: 206-231-3657; email:
julio.c.alvarez@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-2019-1071;
Product Identifier 2019-NM-165-AD" at the beginning of your comments.
The FAA specifically invites comments on the overall regulatory,
economic, environmental, and energy aspects of this NPRM. The FAA will
consider all comments received by the closing date and may amend this
NPRM because of those comments.

The FAA will post all comments we receive, without change, to
https://www.regulations.gov, including any personal information you
provide. The FAA will also post a report summarizing each substantive
verbal contact received about this NPRM.

Discussion

The FAA has received reports indicating the presence of significant
corrosion of electrical connectors located in the MLG wheel well of
airplanes that land on runways treated with deicing fluids containing
potassium formate or potassium acetate. Corrosion and subsequent
moisture ingress may lead to electrical shorting of the connectors.
This condition, if not addressed, can cause incorrect function of
critical systems necessary for safe flight and landing.

Related Rulemaking

AD 2005-18-23, Amendment 39-14264 (70 FR 54253, September 14, 2005)
("AD 2005-18-23"), applies to Boeing Model 737-600, -700, -700C, -
800, and -900 series airplanes, and addresses the same unsafe condition
identified in this NPRM. Model 737-900ER series airplanes were not type
certificated at the time AD 2005-18-23 was issued. The FAA has
therefore determined that this NPRM is necessary to mandate the same
requirements on Model 737-900ER series airplanes.

Related Service Information Under 1 CFR Part 51

This proposed AD would require Boeing Alert Service Bulletin 737-
24A1148, Revision 1, dated July 10, 2003, which the Director of the
Federal Register approved for incorporation by reference as of October
19, 2005 (70 FR 54253, September 14, 2005). 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 require repetitive records checks to
determine exposure to certain deicing fluids or repetitive inspections
for corrosion of electrical connectors, and applicable corrective
actions.

The phrase "corrective actions" is used in this proposed AD.
Corrective actions correct or address any condition found. Corrective
actions in an AD could include, for example, repairs.

Differences Between This Proposed AD and the Service Information

The effectivity of Boeing Alert Service Bulletin 737-24A1148,
Revision 1, dated July 10, 2003, does not specifically identify Model
737-900ER series airplanes; that airplane model was not type
certificated at the time the service information was issued. The
service information does, however, identify the line numbers for Model
737-900ER series airplanes, all of which are in Group 3, so the actions
of that service bulletin are appropriate and can be accomplished on
those airplanes.

Boeing Alert Service Bulletin 737-24A1148, Revision 1, dated July
10, 2003, differs from this proposed AD in the cumulative areas of
backshell corrosion that need corrective action,
and in the compliance time for the respective corrective actions, which
are specified in paragraphs (g)(2)(i) through (ii) of this proposed AD.
These differences have been coordinated with Boeing. The proposed
requirements correspond to three alternative methods of compliance
approved for AD 2005-18-23 and reflect the relief provided for AD 2005-
18-23.

Boeing Alert Service Bulletin 737-24A1148, Revision 1, dated July
10, 2003, specifies that airplanes exposed to affected runway deicing
fluids be inspected for corroded electrical connectors within 12
months. AD 2005-18-23 instead requires initially determining the
airplane's exposure to affected runway deicing fluids within 12 months,
and allows an additional 90 days to inspect for corrosion. For AD 2005-
18-23, the FAA had determined that the additional 90 days for the
inspection represented an acceptable interval of time for affected
airplanes to operate without jeopardizing safety. Therefore, since the
unsafe condition and airplane design are the same in AD 2005-18-23 and
this NPRM, the FAA has determined that 90 days is an appropriate
compliance time for the initial inspection in this proposed AD.

Boeing Alert Service Bulletin 737-24A1148, Revision 1, dated July
10, 2003, and AD 2005-18-23 specify repeating the inspection at 12-
month intervals. However, the FAA determined that a longer interval
would provide an acceptable level of safety. The FAA therefore issued
alternative methods of compliance (AMOCs) for AD 2005-18-23 allowing
this inspection interval to be increased to 24 months. Therefore, this
proposed AD specifies a repetitive inspection interval of 24 months.

Costs of Compliance

The FAA estimates that this proposed AD affects 346 airplanes of
U.S. registry. The FAA estimates the following costs to comply with
this proposed AD:

Estimated Costs

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

On-Condition 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.

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 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 this 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 adding the following new airworthiness
directive (AD):