DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2017-0518; Product Identifier 2016-NM-167-AD; Amendment
39-19064; AD 2017-20-07]
RIN 2120-AA64

Airworthiness Directives; Bombardier, Inc., Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of
Transportation (DOT).

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: We are adopting a new airworthiness directive (AD) for certain
Bombardier, Inc., Model DHC-8-400 series airplanes. This AD was
prompted by the failure of the fire control amplifier (FCA), which was
likely caused by an electrical short in a discharged squib for a fire
extinguishing bottle. This AD requires replacing certain circuit
breakers. We are issuing this AD to address the unsafe condition on
these products.

DATES: This AD is effective November 6, 2017.

The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of November 6,
2017.

ADDRESSES: For service information identified in this final rule,
contact Bombardier, Inc., Q-Series Technical Help Desk, 123 Garratt
Boulevard, Toronto, Ontario M3K 1Y5, Canada; telephone 416-375-4000;
fax 416-375-4539; email thd.qseries@aero.bombardier.com; Internet
http://www.bombardier.com. You may view this referenced service
information at the FAA, Transport Standards Branch, 1601 Lind Avenue
SW., Renton, WA. For information on the availability of this material
at the FAA, call 425-227-1221. It is also available on the Internet at
http://www.regulations.gov by searching for and locating Docket No.
FAA-2017-0518.

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-2017- 0518; or in person at the
Docket Management Facility between 9 a.m. and
5 p.m., Monday through Friday, except Federal holidays. The AD docket
contains this AD, the regulatory evaluation, any comments received, and
other information. The street address for the Docket Office (telephone
800-647-5527) is Docket Management Facility, 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: Assata Dessaline, Aerospace Engineer,
Avionics and Administrative Services Section, FAA, New York ACO Branch,
1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-
7301; fax 516-794-5531.

SUPPLEMENTARY INFORMATION:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 by adding an AD that would apply to certain Bombardier, Inc.,
Model DHC-8-400 series airplanes. The NPRM published in the Federal
Register on June 2, 2017 (82 FR 25554) ("the NPRM"). The NPRM was
prompted by the failure of the FCA, which was likely
caused by an electrical short in a discharged squib for a fire
extinguishing bottle. The NPRM proposed to require replacing certain
circuit breakers. We are issuing this AD to prevent failure of the FCA
and subsequent discharge of fire extinguishing bottles and false fire
indications, leaving the flight crew with reduced firefighting
capability in the event of a fire.

Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued Canadian Airworthiness Directive CF-
2016-25, dated August 22, 2016 (referred to after this as the Mandatory
Continuing Airworthiness Information, or "the MCAI"), to correct an
unsafe condition for certain Bombardier, Inc., Model DHC-8-400 series
airplanes. The MCAI states:

An operator reported having a false SMOKE warning light for the
Aft Baggage compartment, which caused the pilots to discharge the
Aft Baggage compartment fire extinguishing bottles per Aircraft
Flight Manual procedures. Subsequently, there were continuous engine
and Auxiliary Power Unit (APU) fire warning lights, and the fire
extinguishing bottles for both engines (forward and aft) and the APU
were automatically discharged. Post event investigation of the Fire
Control Amplifier (FCA) revealed a burnt 2600-P2 connector. The FCA
was also found to have sustained significant thermal damage. In a
separate event involving a different operator, several fire
extinguishing bottles discharged after an electrical short was
introduced into the FCA by a shorted squib tester (external ground
support equipment) during maintenance.

The FCA manufacturer has identified the most likely failure
condition to be an electrical short at the discharged squib. The
squib's burst disk may have caused a short circuit of the
bridgewires, which caused the FCA's internal power wires to
experience thermal damage, consequently powering other squibs and
fire alarm lines and resulting in the uncommanded discharge of the
fire extinguishing bottles and false fire indications.

Bombardier (BA) has issued service bulletin (SB) 84-26-16 to
change two 7.5 amp circuit breakers to lower current rating 1 amp
circuit breakers to prevent damage to squib discharge circuits and
the inadvertent discharge of fire extinguishing bottles.

This [Canadian] AD mandates the incorporation of [Bombardier] SB
84-26-16 to prevent the inadvertent discharge of fire extinguishing
bottles [leaving the flight crew with reduced firefighting
capability in the event of a fire].

You may examine the MCAI in the AD docket on the Internet at
http://www.regulations.gov by searching for and locating Docket No.
FAA-2017-0518.

Comments

We gave the public the opportunity to participate in developing
this AD. We received no comments on the NPRM or on the determination of
the cost to the public.

Conclusion

We reviewed the relevant data and determined that air safety and
the public interest require adopting this AD as proposed except for
minor editorial changes. We have determined that these minor changes:

Are consistent with the intent that was proposed in the
NPRM for correcting 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

Bombardier, Inc., has issued Service Bulletin 84-26-16, Revision A,
dated February 12, 2016. This service information describes procedures
for locating and replacing certain 7.5-amp circuit breakers with 1-amp
circuit breakers. 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

We estimate that this AD affects 53 airplanes of U.S. registry.
We estimate the following costs to comply with this AD:

Estimated 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.

We are 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 to
the Director of the System Oversight Division.

Regulatory Findings

We 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 Order 12866;

2. Is not a "significant rule" under the DOT Regulatory Policies
and Procedures (44 FR 11034, February 26, 1979);

3. Will not affect intrastate aviation in Alaska; and

4. 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.

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]