DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0161; Product Identifier 2017-NM-088-AD]
RIN 2120-AA64

Airworthiness Directives; Bombardier, Inc., Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to supersede Airworthiness Directive (AD) 2013-11-
12, which applies to certain Bombardier, Inc., Model BD-100-1A10
airplanes. AD 2013-11-12 requires inspecting for the correct serial
number of a certain hydraulic system accumulator, and replacing
affected hydraulic system accumulators with new or serviceable
accumulators. Since we issued AD 2013-11-12, we have determined that
certain other hydraulic system accumulators must be modified or
replaced and life limits must be added. This proposed AD would expand
the applicability and require modifying or replacing certain hydraulic
brake system accumulators. This proposed AD would also require revising
the maintenance or inspection program to add life limits for the
accumulators. We are proposing this AD to address the unsafe condition
on these products.

DATES: We must receive comments on this proposed AD by April 23, 2018.

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.

For service information identified in this NPRM, contact
Bombardier, Inc., 400 Cote-Vertu Road West, Dorval, Quebec
H4S 1Y9, Canada; telephone 514-855-5000; fax 514-855-7401; email
thd.crj@aero.bombardier.com; internet http://www.bombardier.com. You
may view this referenced 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.

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-2018-0161;
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 proposed AD, the regulatory evaluation, any comments
received, and other information. The street address for the Docket
Operations office (telephone 800-647-5527) is in the ADDRESSES section.
Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Cesar Gomez, Aerospace Engineer,
Airframe and Mechanical Systems Section, FAA, New York ACO Branch, 1600
Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7318;
fax 516-794-5531.

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite 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-2018-0161;
Product Identifier 2017-NM-088-AD" at the beginning of your comments.
We specifically invite comments on the overall regulatory, economic,
environmental, and energy aspects of this proposed AD. We will consider
all comments received by the closing date and may amend this proposed
AD based on those comments.

We will post all comments we receive, without change, to http://www.
regulations.gov, including any personal information you provide. We
will also post a report summarizing each substantive verbal contact we
receive about this proposed AD.

Discussion

We issued AD 2013-11-12, Amendment 39-17472 (78 FR 33206, June 4,
2013) ("AD 2013-11-12"), for certain Bombardier, Inc., Model BD-100-
1A10 airplanes. AD 2013-11-12 requires inspecting for the correct
serial number of a certain hydraulic system accumulator, and replacing
affected hydraulic system accumulators with new or serviceable
accumulators. AD 2013-11-12 resulted from reports of failure of a screw
cap or end cap of the hydraulic system accumulator while on the ground,
which resulted in loss of use of that hydraulic system and high-energy
impact damage to adjacent systems and structures. We issued AD 2013-11-12
to prevent failure of a screw cap or end cap and loss of the related
hydraulic system, which could result in damage to airplane structure and
consequent reduced controllability of the airplane.

Actions Since AD 2013-11-12 Was Issued

Since we issued AD 2013-11-12, we have determined that certain
other hydraulic system accumulators (specifically, hydraulic brake
system accumulators) must be modified or replaced and life limits must
be added.

Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued Canadian Airworthiness Directive CF-
2011-41R1, dated March 27, 2017 (referred to after this as the
Mandatory Continuing Airworthiness Information, or "the MCAI"), to
correct an unsafe condition for certain Bombardier, Inc. Model BD-100-
1A10 airplanes. The MCAI states:

Seven cases of on-ground hydraulic accumulator screw cap/end cap
failure have been experienced on CL-600-2B19 aeroplanes, resulting
in loss of the associated hydraulic system and high-energy impact
damage to adjacent systems and structure. To date, the lowest number
of flight cycles accumulated at the time of failure has been 6991.

Although there have been no failures to date on any BD-100-1A10
aeroplanes, accumulators similar to those installed on the CL-600-
2B19 are installed on the BD-100-1A10. The affected part numbers (P/
Ns) of the accumulators installed on BD-100-1A10 are 900095-1
(Auxiliary Hydraulic System accumulator), 33-155500 (Inboard Brake
accumulator), and 33-147500 (Outboard Brake accumulator).

A detailed analysis of the calculated line of trajectory of a
failed screw cap/end cap for the accumulators has been conducted,
resulting in the identification of areas where systems and/or
structural components could potentially be damaged. Although all of
the failures on the CL-600-2B19 to date have occurred on the ground,
an in-flight failure affecting such components could potentially
have an adverse effect on the controllability of the aeroplane.

Revision 1 of this [Canadian] AD is issued to mandate the
[inspection and] replacement [of] Brake System Hydraulic
accumulators that are not identified by the letter "E" or "NAE"
after the serial number on the identification plate. Revision 1 also
mandates the re-orientation of the brake accumulators P/N 33-147500
and P/N 33-155500 and the insertion of three discard tasks in the
Challenger 300 Time Limits/Maintenance Checks (TLMC) Manual.

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-2018-
0161.

Related Service Information Under 1 CFR Part 51

Bombardier, Inc. has issued the following service information:

Service Bulletin 100-32-20, Revision 02, dated April 14,
2015, which describes procedures for modifying (e.g., re-orienting) the
installation of the hydraulic brake accumulators.

Service Bulletin 100-32-21, dated May 24, 2012, which
describes procedures for replacing the hydraulic brake system
accumulators.

Task 29-21-13-101 of Chapter 5, Part 2, Airworthiness
Limitations, of Bombardier Challenger 300 BD-100 Time Limits/
Maintenance Checks, Revision 17, dated December 15, 2016, which
describes procedures for removal and installation of the hydraulic
brake system accumulators.

Task 32-43-37-101 of Chapter 5, Part 2, Airworthiness
Limitations, of Bombardier Challenger 300 BD-100 Time Limits/
Maintenance Checks, Revision 17, dated December 15, 2016, which
describes procedures for removal and installation of the brake
accumulators.

Task 32-44-05-101 of Chapter 5, Part 2, Airworthiness
Limitations, of Bombardier Challenger 300 BD-100 Time Limits/
Maintenance Checks, Revision 17, dated December 15, 2016, which
describes procedures for removal and installation of the emergency
parking brake accumulators.

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 and Requirements of This Proposed AD

This product has been approved by the aviation authority of another
country, and is approved for operation in the United States. Pursuant
to our bilateral agreement with the State of Design Authority, we have
been notified of the unsafe condition described in the MCAI and service
information referenced above. We are proposing this AD because we
evaluated all pertinent information and determined an unsafe condition
exists and is likely to exist or develop on other products of the same
type design.

This proposed AD would require revisions to certain operator
maintenance documents to include new actions (e.g., inspections).
Compliance with these actions is required by 14 CFR 91.403(c). For
airplanes that have been previously modified, altered, or repaired in
the areas addressed by this proposed AD, the operator may not be able
to accomplish the actions described in the revisions. In this
situation, to comply with 14 CFR 91.403(c), the operator must request
approval for an alternative method of compliance according to paragraph
(p)(1) of this proposed AD. The request should include a description of
changes to the required actions that will ensure the continued damage
tolerance of the affected structure.

Costs of Compliance

We estimate that this proposed AD affects 187 airplanes of U.S. registry.

We estimate the following costs to comply with this proposed AD:

Estimated Costs

We estimate the following costs to do any necessary replacements
that would be required based on the results of the inspection. We have
no way of determining the number of aircraft that might need these
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.

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 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. 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.

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)
2013-11-12, Amendment 39-17472 (78 FR 33206, June 4, 2013), and adding
the following new AD: