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Federal Register / Vol. 86, No. 55 / Wednesday, March 24, 2021 / Rules and Regulations
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multiple refuel valves were secured in the open position there could be an uncommanded fuel transfer between fuel tanks. The commenter explained that a review of the fuel control systems on its fleet revealed that the fuel transfer would occur only if two valves were open, each in a different tank. The commenter noted that if only one valve was secured failed open, fuel could enter the manifold but could not migrate into a different tank. The commenter stated that it had contacted Boeing regarding dispatch of an airplane with one refuel valve secured in the open position and that Boeing stated this provides an acceptable level of safety to the proposed AD. The commenter explained that Boeing is developing substantiating analysis to support dispatch of an airplane with one refuel valve secured in the open position for many of the affected airplane models.
In addition, the commenter requested that the repair category be specified as category B three day deferral because the replacement of a refuel valve, which involves fuel tank access and requires specialized training and additional time to properly vent the fuel tanks, would place an undue burden on operators when another acceptable alternative is available.
The FAA does not agree with the commenters requests. The FAA has determined that the operational limitations imposed by this AD are warranted, and adequately address the unsafe condition. Boeing has not yet finalized or provided the FAA with its substantiating analysis to support dispatch of an airplane with one refuel valve secured in the open position.
Boeing has indicated that in the future it might provide updates for the applicable DDG and MMEL for each affected airplane model to provide modified dispatch relief. The FAA has not revised this AD in regard to this issue.
Request To Revise Paragraph h of the Proposed AD To Refer to MEL Instead of MMEL
Boeing requested that the header for paragraph h in the proposed AD be changed from MMEL Items to MEL
Items. The commenter also requested that paragraphs h1 through 6 be revised to refer to MEL items instead of MMEL items. The commenter stated that these changes would provide clarification that MELs would be updated and the wording would be consistent with that of similar ADs.
The FAA partially agrees with the commenters requests. The FAA agrees with the commenters statement that operators will need to update their
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MELs to comply with the change required by this AD. Because dispatch requirements have changed for the applicable airplane models, the FAA
disagrees with removing the reference to the identified MMEL items because this AD does not mandate the actual change to the applicable MMEL. This AD
identifies which FAA-approved MMEL
items are affected. Operators consult the MMEL requirements when updating the operators existing FAA-approved MEL.
The FAA has revised paragraph h of this AD accordingly.
Request To Include Note 2 to Paragraph h of the Proposed AD
Boeing requested that Note 2 be added to paragraph h of the proposed AD
stating that operators must not dispatch an airplane using MMEL Item 282101
with any of the identified valves in the inoperative open condition. The commenter explained that this would prevent dispatch of an airplane with fueling shutoff valves in the inoperative open condition without requiring a reference to a specific chapter of the MMEL.
The FAA disagrees with the commenters request. Not all affected airplanes have MMEL items in section 2821. Further, the intent of the commenters proposed text is adequately addressed in the provisions of paragraph g of this AD, which is unchanged from the proposed AD. The FAA has not changed this AD as a result of this comment.
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 with the changes described previously and 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.
The FAA also determined that these changes will not increase the economic burden on any operator or increase the scope of this final rule.
MMEL Revisions This AD refers to items in Sections 2820 and 2821 of the MMEL; 1 those 1 The
MMEL items can be found in the applicable FAA-approved MMEL: Boeing 747 B747100/200/
300/SP SERIES MMEL, Revision 35, dated April 25, 2014; Boeing 747 B747400 LCF MMEL, Revision 3, November 7, 2014; Boeing 747 B747400, B
747400D, B747400F MMEL, Revision 32, dated
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items may also be included in an operators FAA-approved MEL. This AD
prohibits operation of the airplane under conditions currently allowed by those items in the MMEL. The FAA
plans to revise the MMEL to remove those items in a future revision;
operators would then be required to also remove those items from their existing FAA-approved MEL.
Interim Action The FAA considers this AD interim action. The manufacturer is currently developing an updated MMEL, with substantiation, that would allow limited relief for an inoperative open fuel shutoff valve and mitigate the unsafe condition. Once the updated MMEL is developed, approved, and available, the FAA might consider additional rulemaking.
Costs of Compliance The FAA estimates that this AD
affects 750 airplanes of U.S. registry.
The FAA has determined that revising the operators existing FAA-approved MEL takes an average of 90 work-hours per operator, although the agency recognizes that this number may vary from operator to operator. Since operators typically incorporate MEL
changes for their affected fleets, the FAA has determined that a per-operator estimate is more accurate than a perairplane estimate. Therefore, the FAA
estimates the average total cost per operator to be $7,650 90 work-hours
$85 per work-hour.
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 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 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 December 27, 2018; Boeing 7478 MMEL, Revision 7, dated August 25, 2017; and Boeing 767 MMEL, Revision 39, dated October 26, 2018; which can be found on the Flight Standards Information Management System FSIMS website, https
fsims.faa.gov/PICResults.aspx?mode=Publication&
doctype=MMELByModel.

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