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Federal Register / Vol. 86, No. 84 / Tuesday, May 4, 2021 / Rules and Regulations
SUPPLEMENTARY INFORMATION:

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Background In April 2021, the FAA received a report from CFM, the engine manufacturer, of numerous instances of PSS unit faults. The manufacturer reported these faults have been occurring since October 2020 and are a result of pressure transducer corrosion following extended storage periods. The manufacturers investigation found that certain PSS units, identified by serial number, have been exposed to conditions that make pressure transducers in these units susceptible to an increased rate of faults. These conditions are moisture ingress from long-term on-wing storage, coupled with certain manufacturing processes of the affected pressure transducers. Together these conditions can cause corrosion and subsequent electrical shorting of the pins in the pressure transducer. This short can result in transmittal of erroneous pressure sensor signals to the electronic engine control. Erroneous pressure input from the pressure transducers in the PSS unit has the potential to prevent engine control from meeting thrust demand, thereby resulting in the loss of engine thrust control. Further, the engine manufacturer found that if transmission of erroneous pressure sensor signals were to occur, it would occur within the first 15 hours of electrical power to the PSS unit after the extended storage period is completed. Therefore, the manufacturer recommended that, for engines with fewer than 15 hours of electrical power applied to the PSS unit within the past 90 days, operators either perform a check for engine maintenance messages related to the pressure transducer prior to each flight or apply electrical power to the PSS unit until the PSS unit has accumulated 15 hours or more of electrical power. The FAA is mandating these recommendations in this AD.
This condition, if not addressed, could result in loss of engine thrust control and reduced control of the airplane. The FAA is issuing this AD to address the unsafe condition on these products.
FAAs Determination The FAA is issuing this AD because the agency has determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.
Related Service Information Under 1
CFR Part 51
The FAA reviewed CFM Service Bulletin SB LEAP1B73000038

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01A930AD, Issue 00200, dated 20210425, excluding FADEC Alliance SB LEAP1B/73012, Issue 001, dated 20210423 which is attached to the CFM SB. This SB identifies PSS units with susceptible pressure transducers.
This SB also specifies procedures for checking the engine maintenance messages related to the pressure transducer and applying electrical power to the PSS unit. 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 ADDRESSES.
AD Requirements For an engine in service, this AD
requires checks for engine maintenance messages related to the pressure transducer and, depending on the results of the checks, replacement of the PSS unit before further flight. This AD
requires this repetitive check for faults prior to each flight until the PSS unit has accumulated at least 15 hours of electrical power. For an engine not in service, this AD requires applying electrical power to the PSS unit prior to returning the engine to service.
Interim Action The FAA considers this AD to be an interim action. This unsafe condition is still under investigation by the manufacturer and, depending on the results of that investigation, the FAA
may consider further rulemaking action.
Justification for Immediate Adoption and Determination of the Effective Date Section 553b3B of the Administrative Procedure Act APA 5
U.S.C. 551 et seq. authorizes agencies to dispense with notice and comment procedures for rules when the agency, for good cause, finds that those procedures are impracticable, unnecessary, or contrary to the public interest. Under this section, an agency, upon finding good cause, may issue a final rule without providing notice and seeking comment prior to issuance.
Further, section 553d of the APA
authorizes agencies to make rules effective in less than thirty days, upon a finding of good cause.
An unsafe condition exists that requires the immediate adoption of this AD without providing an opportunity for public comments prior to adoption.
The FAA has found that the risk to the flying public justifies foregoing notice and comment prior to adoption of this rule. As previously noted, there have been numerous instances of PSS units faulting in the last few months. These PSS unit failures can impact the
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capability of the engine control to meet commanded thrust and may lead to a loss of engine thrust control and reduced control of the airplane.
Therefore, the risk created by this unsafe condition requires prompt action, and the FAA is mandating the compliance time for the required action as before further flight. Accordingly, notice and opportunity for prior public comment are impracticable and contrary to the public interest pursuant to 5
U.S.C. 553b3B.
In addition, the FAA finds that good cause exists pursuant to 5 U.S.C. 553d for making this amendment effective in less than 30 days, for the same reasons the FAA found good cause to forego notice and comment. Because of the need for operators to begin the required checks prior to each flight or application of electrical power to the PSS unit, the FAA has made this AD effective 5 days after the date of publication.
Comments Invited The FAA invites you to send any written data, views, or arguments about this final rule. Send your comments to an address listed under ADDRESSES.
Include Docket No. FAA20210346
and Project Identifier AD2021
00465E at the beginning of your comments. The most helpful comments reference a specific portion of the final rule, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this final rule because of those comments.
Except for Confidential Business Information CBI as described in the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to https
www.regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this final rule.
Confidential Business Information CBI is commercial or financial information that is both customarily and actually treated as private by its owner.
Under the Freedom of Information Act FOIA 5 U.S.C. 552, CBI is exempt from public disclosure. If your comments responsive to this AD contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this AD, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as PROPIN. The FAA

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