DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-0758; Project Identifier MCAI-2023-00671-T]
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: The FAA proposes to adopt a new airworthiness directive (AD)
for certain Bombardier, Inc., Model BD-100-1A10 airplanes. This
proposed AD was prompted by the discovery of a single-point failure
within the left-hand and right-hand heater current monitor (HCM) units.
This proposed AD would require installing a monitor circuit comprising
relays external to the HCM units. This proposed AD would also require
revising the normal and non-normal procedure sections of the existing
airplane flight manual (AFM) to add new procedures associated with
revised crew alerting system (CAS) messages. 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 May 9,
2024.

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 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.
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2024-0758; 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, the mandatory continuing airworthiness
information (MCAI), any comments received, and other information. The
street address for Docket Operations is listed above.
Material Incorporated by Reference:
For Bombardier service information identified in this
NPRM, contact Bombardier Business Aircraft Customer Response Center,
400 Cote-Vertu Road West, Dorval, Quebec H4S 1Y9, Canada;
telephone 514-855-2999; email: ac.yul@aero.bombardier.com; website:
bombardier.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.

FOR FURTHER INFORMATION CONTACT: Steven Dzierzynski, Aviation Safety
Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590;
telephone 516-228-7300; 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-2024-0758; Project Identifier
MCAI-2023-00671-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
regulations.gov, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this NPRM.

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
Steven Dzierzynski, Aviation Safety Engineer, FAA, 1600 Stewart Avenue,
Suite 410, Westbury, NY 11590; telephone 516-228-7300; 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.

Background

Transport Canada, which is the aviation authority for Canada, has
issued Transport Canada AD CF-2023-33, dated May 10, 2023 (Transport
Canada AD CF-2023-33) (also referred to after this as the MCAI), to
correct an unsafe condition on certain Bombardier, Inc., Model BD-100-
1A10 airplanes. The MCAI states that during a review of the air data
system, Bombardier discovered that a single-point failure exists within
the left-hand and right-hand HCM units. The HCM unit is designed with a
single programmable logic device (PLD), which is responsible for the
control and monitoring functions of the HCM unit. The PLD could fail in
a way that it would erroneously energize the heater control relay and
switch the heaters off. This failure could lead to un-annunciated loss
of ice protection on the air data probes, resulting in the potential
display of misleading airspeed, and erroneous indications to the
flightcrew.
The FAA is proposing this AD to address the unsafe condition on
these products.
You may examine the MCAI in the AD docket at regulations.gov under
Docket No. FAA-2024-0758.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Bombardier Service Bulletin 100-30-06 and
Bombardier Service Bulletin 350-30-001, both dated December 29, 2022.
The service information specifies procedures to install a monitoring
circuit comprising relays external to the HCM units, including
reworking the plate assembly, installing relay bracket assemblies,
installing relays and a rail terminal module, installing wires for the
relays, and performing operational testing. These documents are
distinct since they apply to different airplane serial numbers.
The FAA also reviewed the following service information, which
specifies new normal procedures to follow after installation of the
monitoring circuit. These documents are distinct since they apply to
different airplane serial numbers.
BEFORE STARTING ENGINES section, Subsection 04-02, Chapter
4, Normal Procedures, Bombardier Challenger 300 AFM (Imperial Version),
Publication No. CSP 100-1, Revision 72, dated May 11, 2023. (For
obtaining the procedures for Bombardier Challenger 300 AFM (Imperial
Version), Publication No. CSP 100-1, use Document Identification No. CH
300 AFM-I.)

BEFORE STARTING ENGINES section, Subsection 04-02, Chapter
4, Normal Procedures, Bombardier Challenger 350 AFM, Publication No. CH
350 AFM, Revision 38, dated May 11, 2023. (For obtaining the procedures
for Bombardier Challenger 350 AFM, Publication No. CH 350 AFM, use
Document Identification No. CH 350 AFM.)
The FAA reviewed the following service information, which specifies
non-normal procedures to follow after installation of the monitoring
circuit. These documents are distinct since they apply to different
airplane serial numbers.
Subsection 05-27, Ice & Rain Protection, Chapter 5, Non-
Normal Procedures, Bombardier Challenger 300 AFM (Imperial Version),
Publication No. CSP 100-1, Revision 72, dated May 11, 2023. (For
obtaining the procedures for Bombardier Challenger 300 AFM (Imperial
Version), Publication No. CSP 100-1, use Document Identification No. CH
300 AFM-I.)
Subsection 05-27, Ice & Rain Protection, Chapter 5, Non-
Normal Procedures, Bombardier Challenger 350 AFM, Publication No. CH
350 AFM, Revision 38, dated May 11, 2023. (For obtaining the procedures
for Bombardier Challenger 350 AFM, Publication No. CH 350 AFM, use
Document Identification No. CH 350 AFM.)
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 this State of Design Authority, it
has notified the FAA of the unsafe condition described in the MCAI and
service information referenced above. The FAA is issuing this NPRM
after determining that the unsafe condition described previously is
likely to exist or develop on other products of the same type design.

Proposed AD Requirements in This NPRM

This proposed AD would require accomplishing the actions specified
in the service information already described. This AD also requires
revising the existing AFM.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 343 airplanes of U.S. registry. The FAA estimates the following
costs to comply with this proposed AD:

Estimated Costs for Required Actions

The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some or all the costs of this
proposed AD may be covered under warranty, thereby reducing the cost
impact on affected operators.

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 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) Would not affect intrastate aviation in Alaska, and
(3) Would 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 adding the following new airworthiness
directive: