DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0018; Project Identifier MCAI-2020-01214-T]
RIN 2120-AA64

Airworthiness Directives; De Havilland Aircraft of Canada Limited
(Type Certificate Previously Held by Bombardier, Inc.) Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD)
2015-17-08, which applies to certain Bombardier, Inc. Model DHC-8-400
series airplanes. AD 2015-17-08 requires installing new cable
assemblies with a pull-down resistor. Since the FAA issued AD 2015-17-
08, a modification has been developed to address all known single point
failures that could lead to runaway of the nose wheel steering (NWS)
system. This proposed AD would require modifications to the NWS system.
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 April 12, 2021.

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 De
Havilland Aircraft of Canada Limited, Q-Series Technical Help Desk, 123
Garratt Boulevard, Toronto, Ontario M3K 1Y5, Canada; telephone 416-375-
4000; fax 416-375-4539; email thd@dehavilland.com; internet https://dehavilland.com.
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.

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-2021-
0018; 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, 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: Siddeeq Bacchus, Aerospace Engineer,
Mechanical Systems and Administrative Services Section, FAA, New York
ACO Branch, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590;
telephone 516-228-7362; fax 516-794-5531; email 9-avs-nyaco-cos@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 ADDRESSES. Include "Docket No. FAA-2021-0018; Project Identifier
MCAI-2020-01214-T" at the beginning of your comments. The most helpful
comments reference a specific portion of the proposal, 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
the proposal 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
https://www.regulations.gov, including any personal information you
provide. The agency will also post a report summarizing each
substantive verbal contact received about this proposed AD.

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 NPRM 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 NPRM, 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 NPRM. Submissions containing CBI should be sent to
Siddeeq Bacchus, Aerospace Engineer, Mechanical Systems and
Administrative Services Section, FAA, New York ACO Branch, 1600 Stewart
Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7362; fax 516-
794-5531; email 9-avs-nyaco-cos@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.

Discussion

The FAA issued AD 2015-17-08, Amendment 39-18241 (80 FR 51459,
August 25, 2015) (AD 2015-17-08), for certain Bombardier, Inc. Model
DHC-8-400 series airplanes. AD 2015-17-08 requires installing new cable
assemblies with a pull-down resistor. AD 2015-17-08 resulted from an
in-service report of an uncommanded and unannunciated nose wheel
steering during airplane pushback from the gate. The FAA issued AD
2015-17-08 to address an uncommanded nose wheel steering during takeoff
or landing in the event of an open circuit in the steering system, and
possible consequent runway excursion.

Actions Since AD 2015-17-08 Was Issued

Since the FAA issued AD 2015-17-08, De Havilland Aircraft of Canada
Limited has developed a modification to address all known single point
failures that could lead to runaway of the NWS system. The FAA
considered AD 2015-17-08 interim action since it did not address all of
the concerns identified during the design review following the incident
that prompted AD 2015-17-08. The FAA has determined that the
modification specified in this proposed AD is necessary to address the
unsafe condition, including concerns not addressed by AD 2015-17-08.

Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued TCCA AD CF-2020-28, dated August 14,
2020 (also referred to after this as the Mandatory Continuing
Airworthiness Information, or the MCAI), to correct an unsafe condition
for certain De Havilland Aircraft of Canada Limited Model DHC-8-401 and
-402 airplanes. You may examine the MCAI in the AD docket on the
internet at https://www.regulations.gov by searching for and locating
Docket No. FAA-2021-0018.

This proposed AD was prompted by a report indicating that several
failure modes of the NWS system may cause the loss of feedback from
both rotary variable differential transformers to the steering control
unit. The FAA is proposing this AD to address failure modes of the NWS
system, which could lead to NWS runaway, loss of directional control of
the airplane, and possible consequent runway excursion. See the MCAI
for additional background information.

Related Service Information Under 1 CFR Part 51

De Havilland Aircraft of Canada Limited has issued Service Bulletin
84-32-162, Revision B, dated November 13, 2019, including UTC Aerospace
Systems Service Bulletin 406300-32-142, dated June 24, 2019; and UTC
Aerospace Systems Service Bulletin 406330-32-143, dated June 24, 2019.
This service information describes procedures for modifying the NWS
system (terminating wiring, reworking the left-hand console frame, and
installing an NWS electronic control unit and NWS hand control). 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

This product has been approved by the aviation authority of another
country, and is approved for operation in the United States. Pursuant
to the FAA's bilateral agreement with the State
of Design Authority, the FAA has been notified of the unsafe condition
described in the MCAI and service information referenced above. The FAA
is proposing this AD because the FAA evaluated all the relevant
information and determined the unsafe condition described previously is
likely to exist or develop on other products of the same type design.

Proposed Requirements of This NPRM

This proposed AD would retain none of the requirements of AD 2015-
17-08. This proposed AD would require accomplishing the actions
specified in the service information described previously.

Costs of Compliance

The FAA estimates that this proposed AD affects 54 airplanes of U.S. registry.

The FAA estimates the following costs to comply with this proposed AD:

Estimated Costs for Required Actions

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

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 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 removing Airworthiness Directive (AD)
2015-17-08, Amendment 39-18241 (80 FR 51459, August 25, 2015), and
adding the following new AD: