Airworthiness Directives; Bombardier, Inc., Airplanes

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2023-11-01, Amendment 39-22446 (88 FR 44042, July 11, 2023) (AD 2023-11-01). AD 2023-11-01 applied to certain Bombardier, Inc., Model BD-100-1A10 airplanes. AD 2023-11-01 required a records check and replacement of affected LH DCPC units, and provided optional terminating action for those actions. The FAA issued AD 2023-11-01 to address erratic indications, which could cause the flight crew to turn off fully-operational electrical power sources, leading to partial or complete loss of electrical power resulting in loss of flight displays and reduced controllability of the airplane.

The NPRM published in the Federal Register on April 26, 2024 (89 FR 32380). The NPRM was prompted by AD CF-2023-35, dated May 26, 2023, issued by Transport Canada, which is the aviation authority for Canada (Transport Canada AD CF-2023-35) (also referred to as the MCAI). The MCAI states that airplanes could experience misleading electrical system status indications (PBA and EICAS) as a result of contamination of electrical contacts in the LH DCPC internal communication data bus.

In the NPRM, the FAA proposed to continue to require checking the airplane records and replacement of affected LH DCPC units. The NPRM also proposed to require modification of certain LH DCPC units, prohibit installation of affected parts, and expand the applicability of AD 2023-11-01. 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-2024-1003.

Discussion of Final Airworthiness Directive

Comments

The FAA received a comment from Bombardier, Inc. (Bombardier), who also stated its support for the NPRM. The following presents the comment received on the NPRM and the FAA's response to that comment.

Request To Extend the Compliance Time

Bombardier requested that the proposed AD be revised to extend the proposed compliance time to March 31, 2026. Bombardier asserted that, due to changes made in the airplane flight manual (AFM), which introduced the “Unexpected Electrical Indications” procedure instructing pilots not to act on erratic indications related to the electrical power generation and distribution system, the medium risk was mitigated and the severity of a misleading indication event was lowered from potentially catastrophic to major. Even if such events still occur after the implementation of Bombardier Service Bulletins 100-24-30 and 350-24-005, following implementation of the AFM revision, Bombardier considers these events a reliability issue and stated its commitment to work with the supplier to correct the effects of such events. Bombardier further asserted that, when analyzed in conjunction with the probability of occurrence, the risk becomes low. Additionally, Bombardier attested that, based on its provisions, a shorter compliance time will create additional pressure on the U.S. operators, exposing them to a potential grounding scenario, necessitating the need for Bombardier to apply for an alternative method of compliance (AMOC) to support this AD.

The FAA disagrees with the request. Bombardier provided no substantiating data to support the need for an extension of the proposed compliance time. In developing an appropriate compliance time for this action, the FAA considered the safety implications, the time necessary to accomplish the required actions, the availability of required parts, and normal maintenance schedules for timely accomplishment of the required actions. Considering these items, the FAA has determined that the specified compliance time, as proposed, is appropriate to ensure an acceptable level of safety. The FAA has not changed this AD because of this comment. However, under the provisions of paragraph (m)(1) of this AD, the FAA will consider requests for approval of alternative compliance times if sufficient data are submitted to substantiate that the change would provide an acceptable level of safety.

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 Bulletins 100-24-29 and 350-24-004, both Revision 01, both dated July 27, 2023. This material specifies procedures for a records check to determine the total flight hours and replacement of affected LH DCPC units (part numbers 975GC02Y04, 975GC0Y05, 975GC02Y06, and 975GC02Y07). These documents are distinct since they apply to different airplane configurations.

The FAA also reviewed Subject 24-61-01 DC Power Center (DCPC)—Removal/Installation, Chapter 24—Electrical Power, Bombardier Challenger 300 Aircraft Maintenance Manual, Part Two, Publication No. CH 300 AMM, Revision 82, dated November 9, 2023, which specifies:

• procedures for removing DCPC units in Task 24-61-01-000-801 Removal of the DC Power Center (DCPC);
• procedures for installing DCPC units in Task 24-61-01-400-801 Installation of the DC Power Center (DCPC); and
• procedures for testing DCPC units in Task 24-61-01-720-801 Functional Test of the DC Power Center (DCPC).

For obtaining these tasks for the Bombardier Challenger 300 Aircraft Maintenance Manual, Part Two, Publication No. CH 300 AMM, use Document Identification No. CH 300 AMM.

The FAA also reviewed Subject 24-61-01 DC Power Center (DCPC)—Removal/Installation, Chapter 24—Electrical Power, Bombardier Challenger 350 Aircraft Maintenance Manual, Part Two, Publication No. CH 300 AMM, Revision 38, dated November 9, 2023, which specifies:

• procedures for removing DCPC units in Task 24-61-01-000-801 Removal of the DC Power Center (DCPC);
• procedures for installing DCPC units in Task 24-61-01-400-801 Installation of the DC Power Center (DCPC); and
• procedures for testing DCPC units in Task 24-61-01-720-801 Functional Test of the DC Power Center (DCPC).

For obtaining these tasks for the Bombardier Challenger 350 Aircraft Maintenance Manual, Part Two, Publication No. CH 350 AMM, use Document Identification No. CH 350 AMM.

This AD would also require the following material, which the Director of the Federal Register approved for incorporation by reference as of August 15, 2023 (88 FR 44042, July 11, 2023).

• Bombardier Service Bulletin 100-24-29, dated April 9, 2021.
• Bombardier Service Bulletin 100-24-30, dated November 29, 2022.
• Bombardier Service Bulletin 350-24-004, dated April 9, 2021.
• Bombardier Service Bulletin 350-24-005, dated November 29, 2022.

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 356 airplanes of U.S. registry.

The FAA estimates the following costs to comply with this AD: