Discussion \n\n\n\tThe FAA has received a report indicating that a Boeing Model 787 airplane equipped with General Electric Company (GE) GEnx-1B model turbofan engines experienced temporary thrust anomalies on both engines during descent into Kansai, Japan, on March 29, 2019. Specifically, both engines briefly fell below idle thrust, and the flightcrew received failure messages for both engines. \n\tThe FAA's review of the data from this incident indicated the thrust anomalies resulted from fuel control instability. The fuel tanks of the event airplane had recently been treated with Kathon FP 1.5 biocide for suspected microbial growth contamination. Salt crystals can form in the fuel under certain conditions after Kathon FP 1.5 biocide is applied. These salt crystals have the potential to cause slow response of engine hydromechanical control features, resulting in compressor stalls or flameouts, potentially on both engines. \n\tHaving similar fuel system architecture as the GE GEnx engines, the CFM International S.A. (CFM) LEAP-1B model turbofan engines, which are installed on 737 MAX airplanes, are also considered susceptible to a multi-engine loss-of-thrust-control event. This condition, if not addressed, could result in malfunction of the engine's control system hydromechanical unit due to undispersed Kathon FP 1.5 biocide contaminating and restricting the movement of internal parts. Because the fuel systems for both engines on an affected airplane are likely to be similarly affected, there is the potential for loss of thrust control on both engines. Loss of thrust control on both engines could result in failure to climb on takeoff, a forced off-airport landing, or an unacceptably high flightcrew workload. \n\tHowever, after this biocide is added to the fuel tanks, adding fuel without biocide diminishes the hazard. Eventually, after the tanks have been refilled a sufficient number of times with untreated fuel, enough of the treated fuelis gone that the unsafe condition has been removed. Specifically, Boeing determined that operating the airplane, or any individual engine, for at least 30 flight cycles, while adding only fuel that has not been treated with this biocide, would flush the biocide from the fuel tank system and the engines. The FAA finds this number of flight cycles to be sufficiently conservative, and therefore has incorporated it the requirements of this AD. \n\tThe FAA's analysis of the risks posed by this issue has been ongoing, as has the information available to the agency. On March 10, 2020, the manufacturer of Kathon FP 1.5 withdrew that product from the aviation market, effective immediately. A copy of that letter is in the docket for this rulemaking. On March 25, 2020, the FAA issued a Special Airworthiness Information Bulletin (SAIB), which is in the docket for this rulemaking, regarding the effects of Kathon FP 1.5 and another biocide. Most recently, on June 25, 2020, the Japan Transport SafetyBoard issued an ''Aircraft Serious Incident Investigation Report'' regarding the March 29, 2019 incident. That report is in the docket for this rulemaking. \n\tThe FAA may consider similar rulemaking to address the unsafe condition on other airplane models, such as the aforementioned Boeing 787, pending findings from further investigation of other engines. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tThe FAA reviewed Boeing Multi-Operator Message MOM-MOM-20-0522-01B, dated June 24, 2020, which describes procedures for removing Kathon FP 1.5 biocide from the fuel tanks and engines. 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. \n\nFAA's Determination \n\n\n\tThe FAA is issuing this AD because the agency evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design. \n\nAD Requirements \n\n\n\tThis AD requires removing Kathon FP 1.5 biocide from the fuel tanks and engines, installing a fuel limitation placard, and revising the existing AFM to prohibit operation of the airplane with Kathon FP 1.5 biocide in a fuel tank or engine. \n\nJustification for Immediate Adoption and Determination of the Effective Date \n\n\n\tSection 553(b)(3)(B) 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 553(d) of the APA authorizes agencies to make rules effective in less than thirty days, upon a finding of good cause. \n\tAn 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 flightcrews justifies foregoing notice and comment prior to adoption of this rule because the simultaneous loss of thrust control on both engines, due to malfunction of the engine's control system hydromechanical unit due to undispersed Kathon FP 1.5 biocide contaminating and restricting the movement of internal parts, could result in failure to climb on takeoff, a forced off-airport landing, or an unacceptably high flightcrew workload. In addition, the compliance time for the required action is shorter than the time necessary for the public to comment and for publication of the final rule. The FAA acknowledges that it prohibited most operations of airplanes covered by this AD, by emergency order dated March 13, 2019, a copy of which is in the docket for this rulemaking. However, that order allows these airplanes to be operated without carrying passengers, for specific purposes such as repairs, alterations, maintenance, and production flight testing. Therefore this rule must be issued immediately, to ensure the safety of the flightcrews conducting such flights. Accordingly, notice and opportunity for prior public comment are impracticable and contrary to the public interest pursuant to 5 U.S.C. 553(b)(3)(B). \n\tIn addition, the FAA finds that good cause exists pursuant to 5 U.S.C. 553(d) for making this amendment effective in less than 30 days, for the same reasons the FAA found good cause to forgo notice and comment. \n\nComments Invited \n\n\n\tThe FAA invites you to send any written data, views, or arguments about this final rule. Send your comments to an address listed under the ADDRESSES section. Include the docket number FAA-2020-0579 and Product Identifier 2020-NM-009-AD at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing \n\n((Page 42691)) \n\ndate and may amend this final rule because of those comments. \n\tExcept 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 FAA will also post a report summarizing each substantive verbal contact received about this final rule. \n\nConfidential Business Information \n\n\n\tCBI 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 will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this AD. Submissions containing CBI should be sent to Christopher Baker, Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-231-3552; email: Christopher.R.Baker@faa.gov. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking. \n\nRegulatory Flexibility Act (RFA) \n\n\n\tThe requirements of the RFA do not apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt a rule without prior notice and comment. Because the FAA has determined that it has good cause to adopt this rule without notice and comment, RFA analysis is not required. \n\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD affects 75 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: \n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per Cost on U.S. \n\tAction Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Kathon FP 1.5 biocide removal Up to 24 work-hours x $30................. $2,070 Up to $155,250. \n\t$85 per hour = Up to \n\t$2,040. Fueling placard installation. 2 work-hours x $85 Minimal............. 170 12,750. \n\tper hour = $170. AFM revision................. 1 work-hour x $85 per 0................... 85 6,375. \n\thour = $85. ---------------------------------------------------------------------------------------------------------------- \n\nAuthority for This Rulemaking \n\n\n\tTitle 49 of the United States Code specifies the FAA's 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 Agency's authority. \n\tThe 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 unsafe condition that is likely to exist or develop on products identified in this rulemaking action. \n\nRegulatory Findings \n\n\n\tThis AD will not have federalism implications under Executive Order 13132. This AD will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. \n\tFor the reasons discussed above, I certify that this AD: \n\t(1) Is not a ''significant regulatory action'' under Executive Order 12866, and \n\t(2) Will not affect intrastate aviation in Alaska. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.