DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-0758; Project Identifier MCAI-2023-00671-T;
Amendment 39-22819; AD 2024-16-13]
RIN 2120-AA64

Airworthiness Directives; Bombardier, Inc., Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain Bombardier, Inc., Model BD-100-1A10 airplanes. This AD was
prompted by the discovery of a single-point failure within the left-
hand and right-hand heater current monitor (HCM) units. This AD
requires installing a monitor circuit comprising relays external to the
HCM units. This AD also requires 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 issuing this AD to address the unsafe condition on
these products.

DATES: This AD is effective October 29, 2024.

The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of October 29, 2024.

ADDRESSES:

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 final rule, the mandatory continuing airworthiness
information (MCAI), 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.

Material Incorporated by Reference:

For Bombardier material identified in this AD, contact
Bombardier Business Aircraft Customer Response Center, 400 Cote-
Vertu Road West, Dorval, Quebec H4S 1Y9, Canada; telephone 514-
855-2999; email: bombardier.com">ac.yul@aero.bombardier.com; website: bombardier.com.

You may view this material 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 at regulations.gov under
Docket No. FAA-2024-0758.

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:

Background

The FAA 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 BD-100-1A10 airplanes. The NPRM published in the Federal
Register on March 25, 2024 (89 FR 20562). The NPRM was prompted by AD
CF-2023-33, dated May 10, 2023 (referred to after this as the MCAI),
issued by Transport Canada, which is the aviation authority for Canada.
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.

In the NPRM, the FAA proposed to require installing a monitor
circuit comprising relays external to the HCM units. The NPRM also
required revising the normal and non-normal procedure sections of the
existing AFM to add new procedures associated with revised CAS
messages. The FAA is issuing 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.

Discussion of Final Airworthiness Directive

Comments

The FAA received a comment from NetJets Inc. The following presents
the comment received on the NPRM and the FAA's response to the comment.

Request to Reference Previous AFM Revision

NetJets requested that the NPRM be revised to change references to
Bombardier Challenger 350 AFM, Publication No. CH 350 AFM, Revision 38,
dated May 11, 2023 (Revision 38), to Revision 36, dated September 27,
2022 (Revision 36), which is referenced in the MCAI for Challenger 350
airplanes. NetJets pointed out that the particular procedures affected
by the proposed AD were amended in Revision 36. Further, NetJets stated
that Revision 38 is out-of-date and speculated that chances are good
that, if the FAA changes to Revision 39, dated September 25, 2023
(Revision 39), Bombardier will issue a new revision before the final AD
is released. NetJets went on to assert that this will cause an
increased workload for the FAA, Bombardier, and operators due to the
increase in necessary requests for approvals of alternative methods of
compliance (AMOCs) to use later revisions of the AFM.

The FAA does not agree to revise this AD to change the AFM revision
but provides the following clarification: Paragraphs (h)(3) and (4)
specify to revise Chapter 4, Normal Procedures, to include the
information in BEFORE STARTING ENGINES section, Subsection 04-02, and
in Chapter 5, Non-Normal Procedures, to include the information in
Subsection 05-27, Ice & Rain Protection, respectively, of the
Bombardier Challenger 350 AFM, Publication No. CH 350 AFM, Revision 38,
dated May 11, 2023 (for the applicable airplanes). The language in
paragraph (h) of this AD is designed to allow incorporating the
information in the referenced sections, regardless of the revision
level of the AFM, so long as the language is identical to the
information in BEFORE STARTING ENGINES section, Subsection 04-02,
Chapter 4, Normal Procedures, and Subsection 05-27, Ice & Rain
Protection, Chapter 5, Non-Normal Procedures, of the Bombardier
Challenger 350 AFM, Publication No. CH 350 AFM, Revision 38, dated May
11, 2023. The information in BEFORE STARTING ENGINES section,
Subsection 04-02, Chapter 4, Normal Procedures, and Subsection 05-27,
Ice & Rain Protection, Chapter 5, Non-Normal Procedures, of the
Bombardier Challenger 350 AFM, Publication No. CH 350 AFM, Revision 38
is identical to that in Revision 36. Therefore, this AD has not been
changed regarding this request.

Conclusion

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
referenced above. The FAA reviewed the relevant data, considered the
comment received, and determined that air safety requires adopting this
AD as proposed. Accordingly, the FAA is issuing this AD to address the
unsafe condition on this product. Except for minor editorial changes,
this AD is adopted as proposed in the NPRM. None of the changes will
increase the economic burden on any operator.

Material Incorporated by Reference 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.
This material 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 material, 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 material, 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 material 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 343 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this 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
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

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) 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
reference, Safety.

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 adding the following new airworthiness
directive: