DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2021-0018; Project Identifier MCAI-2020-01214-T;
Amendment 39-21546; AD 2021-10-13]
Airworthiness Directives; De Havilland Aircraft of Canada Limited
(Type Certificate Previously Held by Bombardier, Inc.) Airplanes
AGENCY: Federal Aviation Administration (FAA), Department of
ACTION: Final rule.
SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2015-17-
08, which applied to certain Bombardier, Inc. Model DHC-8-400 series
airplanes. AD 2015-17-08 required installing new cable assemblies with
a pull-down resistor. This AD requires modifications to the nose wheel
steering (NWS) system. This 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 issuing this AD to address the unsafe
condition on these products.
DATES: This AD is effective July 1, 2021.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of July 1,
ADDRESSES: For service information identified in this final rule,
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 email@example.com;
internet https://dehavilland.com. You may view this referenced 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 on the internet at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0018.
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 final rule, any comments received, and other information. The
address for Docket Operations is U.S. Department of Transportation,
Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200
New Jersey Avenue SE, Washington, DC 20590.
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 firstname.lastname@example.org.
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 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.
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 to supersede AD 2015-17-08, Amendment 39-18241 (80 FR
51459, August 25, 2015) (AD 2015-17-08). AD 2015-17-08 applied to
certain Bombardier, Inc. Model DHC-8-400 series airplanes. The NPRM
published in the Federal Register on February 24, 2021 (86 FR 11175).
The NPRM 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
NPRM proposed to require modifications to the NWS system. The FAA is
issuing 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
The FAA gave the public the opportunity to participate in
developing this final rule. The FAA has considered the comment
received. The Air Line Pilots Association, International (ALPA)
indicated its support for the NPRM.
The FAA reviewed the relevant data, considered the comment
received, and determined that air safety and the public interest
require adopting this final rule as proposed, except for minor
editorial changes. The FAA has determined that these minor changes:
Are consistent with the intent that was proposed in the
NPRM for addressing the unsafe condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM.
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.
Costs of Compliance
The FAA estimates that this AD affects 54 airplanes of U.S.
The FAA estimates the following costs to comply with this AD:
Estimated Costs for Required Actions
||13 work-hours x $85 per hour
||Up to $122
||Up to $1,227
||Up to $66,258
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.
The FAA determined that 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
(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
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:
a. Removing Airworthiness Directive (AD) 2015-17-08, Amendment 39-18241
(80 FR 51459, August 25, 2015); and
b. Adding the following new AD: