DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2018-0790; Product Identifier 2018-NM-078-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) 2010-14-
05, which applies to certain Bombardier, Inc., Model CL-600-1A11 (600),
CL-600-2A12 (601), and CL-600-2B16 (601-3A, 601-3R, and 604 Variants)
airplanes. AD 2010-14-05 requires inspection for the part numbers of
the system and brake accumulators, and repetitive replacement of
affected accumulators. Since we issued AD 2010-14-05, we have
determined that new or more restrictive airworthiness limitations, as
well as additional actions, are necessary to address the unsafe
condition. In addition to the requirements of AD 2010-14-05, this
proposed AD would require relocating the accumulators and revising the
maintenance or inspection program to incorporate new or more
restrictive airworthiness limitations. This proposed AD would also add
optional terminating action for certain airplanes. We are proposing
this AD to address the unsafe condition on these products.

DATES: We must receive comments on this proposed AD by October 29, 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; Widebody Customer Response Center North America toll-
free telephone 1-866-538-1247 or direct-dial telephone 1-514-855-2999;
fax 514-855-7401; email ac.yul@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-
0790; 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 NPRM, 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: Neil Doh, Aerospace Engineer, Aviation
Safety Section AIR-7B1, Boston ACO Branch, FAA, 1200 District Avenue,
Burlington, MA 01803; telephone 781-238-7757.

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-2018-0790;
Product Identifier 2018-NM-078-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 2010-14-05, Amendment 39-16350 (75 FR 37994, July 1,
2010) ("AD 2010-14-05"), for certain Bombardier Model CL-600-1A11
(600), CL-600-2A12 (601), CL-600-2B16 (601-3A, 601-3R, and 604 Variants
(including CL-605 Marketing Variant)) airplanes. AD 2010-14-05 requires
an inspection to determine the part numbers of the system accumulators
numbers 1, 2, and 3 and brake accumulators numbers 2 and 3, and
repetitive replacement of the accumulator. AD 2010-14-05 resulted from
reports of the on-ground failure of the hydraulic accumulator screw cap
or end cap, resulting in loss of the associated hydraulic system and
high-energy impact damage to adjacent systems and structure. We issued
AD 2010-14-05 to address failure of one of the brake accumulator screw
caps/end caps, resulting in impact damage causing loss of both
hydraulic systems No. 2 and No. 3, with consequent loss of both braking
and nose wheel steering and the potential for a runway excursion.

Actions Since AD 2010-14-05 Was Issued

Since we issued AD 2010-14-05, we have determined that new or more
restrictive airworthiness limitations and additional actions are
necessary to address the unsafe condition.

Transport Canada Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued Canadian AD CF-2009-39R1, issued
October 13, 2017 (referred to after this as the Mandatory Continuing
Airworthiness Information, or "the MCAI"), to correct an unsafe
condition for certain Bombardier, Inc., Model CL-600-1A11 (600), CL-
600-2A12 (601), and CL-600-2B16 (601-3A, 601-3R, and 604 Variants)
airplanes. The MCAI states:

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

Although there have been no failures to date on any CL-600-1A11,
CL-600-2A12 or CL-600-2B16 aircraft, the same accumulators as those
installed on the CL-600-2B19, Part Numbers (P/N) 08-60163-002 and
08-60164-002 are installed on some of the aircraft listed in the
Applicability section of this directive.

Notes:

1. Earlier accumulators, P/Ns 2770571-102, 2770571-103, 2770571-
104 and 2770571-105, were installed in production on the following
aircraft: CL-600-1A11 [all Serial Numbers (S/Ns)], CL-600-2A12 (all
S/Ns) and CL-600-2B16 (S/Ns 5001 through 5194 and 5301 through 5524
only). These accumulators do not require inspection or replacement.
However, if any of the accumulators with the above P/Ns have been
replaced in-service by P/Ns 08-60163-002 and 08-60164-002, these
latter accumulators require replacement.

2. Prior to issuance of [Canadian] AD CF-2009-39, the only
accumulators ever installed in production on CL-600-2B16
aircraft, S/Ns 5525 through 5665 and 5701 through 5908, are P/Ns 08-
60163-002 and 08-60164-002; these accumulators require replacement.

3. After issuance of [Canadian] AD CF-2009-39 [which
corresponded to FAA AD 2010-14-05, Amendment 39-16350 (75 FR 37994,
July 1, 2010)], accumulators with P/Ns specified in Note 2, above,
began to feature various S/N suffixes. Only accumulators with S/N
suffix "TNAE" do not require replacement, but they are subject to
other mandatory actions detailed in this AD.

4. Stainless steel accumulators P/Ns 601R75139-3 (11094-4) and
601R75139-1 (11093-4) were installed in production on CL-600-2B16
aircraft, S/Ns 5909 and subsequent. These accumulators do not
require replacement, but they are subjected to other mandatory
actions detailed in this AD.

A detailed analysis of the systems and structure in the
potential line of trajectory of a failed screw cap/end cap for each
accumulator, P/Ns 08-60163-002 and 08-60164-002, has been conducted.
On the Challengers, it has been identified that the worst case
scenario would be a failure of system No. 1, 2 or 3 accumulator
screw caps/end caps (depending on the model), resulting in a
potential uncontrolled fire in a non-designated fire zone.

The original version of this [Canadian] AD gave instructions to
perform identification and records checks, where applicable, and
replace accumulators, P/Ns 08-60163-002 and 08-60164-002 within the
time compliance specified.
* * * * *

The unsafe condition is potential impact damage that could cause
loss of both hydraulic systems No. 2 and No. 3, and the consequent loss
of both braking and nose wheel steering, the potential for a runway
excursion, and damage to the airplane. Required actions include
relocating certain accumulators. 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-2018-0790.

Related Service Information Under 1 CFR Part 51

The following Bombardier service information describes procedures
for replacing hydraulic system accumulators with new, overhauled, or
refurbished accumulators. These documents are distinct since they apply
to different airplane models.

Service Bulletin 600-742, Revision 4, dated June 11, 2015
Service Bulletin 601-597, Revision 4, dated June 11, 2015
Service Bulletin 604-29-008, Revision 4, dated June 11, 2015
Service Bulletin 605-29-001, Revision 4, dated June 10, 2015

The following Bombardier service information describes procedures
for relocating hydraulic system accumulators. These documents are
distinct since they apply to different airplane models in different
configurations.

Service Bulletin 600-0764, dated October 8, 2015
Service Bulletin 600-0767, dated August 25, 2016
Service Bulletin 601-0633, dated October 8, 2015
Service Bulletin 601-0637, dated August 25, 2016
Service Bulletin 604-29-013, Revision 2, dated April 18, 2016
Service Bulletin 605-29-006, Revision 2, dated April 19, 2016

The following Bombardier Time Limits/Maintenance Checks describe
certain systems life limits of the safe life items. These documents are
distinct since they apply to different airplane models in different
configurations.

Bombardier Challenger 600 Time Limits/Maintenance Checks, PSP
605, Revision 39, dated January 8, 2018
Bombardier Challenger 601 Time Limits/Maintenance Checks, PSP
601-5, Revision 46, dated January 8, 2018
Bombardier Challenger 601 Time Limits/Maintenance Checks, PSP
601A-5, Revision 42, dated January 8, 2018
Bombardier Challenger 604 CL-604 Time Limits/Maintenance
Checks, Revision 30, dated December 4, 2017
Bombardier Challenger CL-605 Time Limits/Maintenance Checks,
Revision 18, dated December 4, 2017

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 designs.

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
(n)(1) of this proposed AD. The request should include a description of
changes to the required inspections that will ensure the continued
operational safety of the airplane.

Difference Between Proposed AD and MCAI

Although the MCAI placed no restrictions on special flight permits,
this proposed AD would limit ferry flights by requiring an engineering
recommendation from Bombardier as well as approval from the Flight
Standards District Office. This difference has been coordinated with
TCCA.

Costs of Compliance

We estimate that this proposed AD affects 130 airplanes of U.S.
registry. We estimate the following costs to comply with this proposed
AD:

Estimated Costs for Required Actions

For the new maintenance/inspection program revision, we have
determined that this action takes an average of 90 work-hours per
operator, although we recognize that this number may vary from operator
to operator. In the past, we have estimated that this action takes 1
work-hour per airplane. Since operators incorporate maintenance or
inspection program changes for their affected fleet, we have determined
that a per-operator estimate is more accurate than a per-airplane
estimate. Therefore, we estimate the total cost per operator to be
$7,650 (90 work-hours x $85 per work-hour).

According to the manufacturer, some or all of the costs of this
proposed AD may be covered under warranty, thereby reducing the cost
impact on affected individuals. We do not control warranty coverage for
affected individuals. As a result, we have included all known costs in
our cost estimate.

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 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 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)
2010-14-05, Amendment 39-16350 (75 FR 37994, July 1, 2010), and adding
the following new AD: