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Federal Register / Vol. 86, No. 106 / Friday, June 4, 2021 / Rules and Regulations
the Accomplishment Instructions from this ADs requirements. The Job Set-up sections of the required service bulletins include specific procedures for the electrical power and proper configurations of the nose landing gear NLG and MLG, which are necessary for accomplishing the applicable corrective actions on the PSEUs and proximity detectors and to prevent possible damage to that equipment.
Requiring the Job Set-up instructions should not, in general, restrict the ability to schedule other maintenance actions in conjunction with the required actions. The FAA has not changed this AD in this regard.
Request To Allow Use of Alternative Service Information When Installing a Certain Part Horizon Air requested that paragraph i of the proposed AD be revised to also allow installation of PSEU part number P/N 301450602 in accordance with Bombardier Service Bulletin 8432143, Revision B, dated November 16, 2016.
Horizon Air pointed out that both documents stated that operators may receive a PSEU with P/N 301450601 or 301450602. Further, Horizon Air noted that PSEU P/N 301450602 is two-way interchangeable with P/N 301450601, and that the installation instructions are the same in both service bulletins.
The FAA disagrees with the request to revise paragraph i of this AD. The FAA
agrees that the service information does state a two-way interchangeability of PSEU P/N 301450601 with PSEU P/N

301450602 and that operators may receive either PSEU P/N due to component availability. However, the service information also states that those in receipt of a PSEU must declare the appropriate service information specific to the PSEU P/N. In addition, while most of the Accomplishment Instructions between Bombardier Service Bulletin 8432143, Revision B, dated November 16, 2016, and Bombardier Service Bulletin 8432149, dated November 16, 2016, are the same, they are not identical. Therefore, recording compliance with another service bulletin would not be in compliance with the applicable corrective actions for the PSEU P/N. The FAA has not changed the AD in this regard.
Conclusion The FAA reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this final rule as proposed, except for minor editorial changes. The FAA has determined that these minor changes:
Are consistent with the intent that was proposed in the NPRM for addressing the unsafe condition; and Do not add any additional burden upon the public than was already proposed in the NPRM.
Related Service Information Under 1
CFR Part 51
De Havilland Aircraft of Canada Limited has issued Bombardier Service
Bulletin 8432140, Revision B, dated January 30, 2018. This service information describes set-up procedures for proper configuration of the MLG
prior to performing subsequent procedures for inspections for correct height of the lock link over-center stop pin and for correct gaps of the left-hand and right-hand MLG downlock proximity sensors, and replacement of the shim.
De Havilland Aircraft of Canada Limited has also issued Bombardier Service Bulletin 8432143, Revision B, dated November 16, 2016, which describes procedures for installation of a new, improved PSEU, P/N 30145
0601, with software changes.
De Havilland Aircraft of Canada Limited has also issued Bombardier Service Bulletin 8432149, dated November 16, 2016, which describes procedures for installation of a new, improved PSEU, P/N 301450602, with software changes.
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.
Costs of Compliance The FAA estimates that this AD
affects 57 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD:

ESTIMATED COSTS FOR REQUIRED ACTIONS
Cost on U.S.
operators
Labor cost
Parts cost
Cost per product
Up to 12 work-hours $85 per hour = Up to $1,020

Up to $4,750

Up to $5,770

The FAA estimates the following costs to do any necessary on-condition actions that would be required based on
the results of any required actions. The FAA has no way of determining the
Up to $328,890.

number of aircraft that might need these on-condition actions:

ESTIMATED COSTS OF ON-CONDITION ACTIONS
Labor cost
Parts cost
Cost per product
1 work-hour $85 per hour = $85

$374

$459

Authority for This Rulemaking Title 49 of the United States Code specifies the FAAs 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
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detail the scope of the Agencys 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
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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
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