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AGENCY:
Federal Aviation Administration (FAA), DOT.
ACTION:
Final rule.
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 Côte-Vertu Road West, Dorval, Québec H4S 1Y9, Canada; telephone 514-855-2999; email: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 atregulations.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
| Labor cost | Parts cost | Cost per product | Cost on U.S. operators |
|---|---|---|---|
| Up to 70 work-hours × $85 per hour = Up to $5,950 | Up to $2,324 | Up to $8,274 | Up to $2,837,982 |