Discussion \n\n\n\tIn May 2019, Boeing informed the FAA that alteration of thrust reverser upper locking actuators, in accordance with unapproved data in the Boeing AMM, could cause a locking mechanism failure of a thrust reverser upper locking actuator to remain undetected for thousands of flights. \n\tBoeing informed the FAA of the risk that operators could use an existing AMM procedure that was intended for use in rigging a newly installed thrust reverser upper locking actuator to instead alter the functioning of a worn upper locking actuator's lock indication. That procedure removes material from the upper locking actuator's lock sensor target until the upper locking actuator's unlocked indication (the ''REVERSER'' light on the flight deck aft overhead panel, which is illuminated when the upper locking actuator is unlocked or when other system failures are detected) is no longer illuminated. However, that procedure does not require a check to verify that the thrust reverser upper locking actuator locking mechanism is operative or that the unlocked indication functions normally after removal of the material. As a result, it is possible that use of this procedure could prevent actuator unlocked indications to the flight crew if the thrust reverser upper locking actuator locking mechanism has already failed or subsequently fails. \n\tAn undetected unlocked thrust reverser upper locking actuator in flight significantly increases the likelihood of an in-flight deployment of the thrust reverser. In-flight thrust reverser deployment in some phases of flight would likely result in loss of airplane control. \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 revising the existing maintenance or inspection program to remove certain text from all locations in the existing maintenance and inspection program that instructs the maintainers to remove material from or grind or trim the sensor target of the thrust reverser upper locking actuator. For Model 737-600, -700, -700C, -800, -900, and -900ER series (737 NG) airplanes, this AD also requires repetitive integrity tests of the thrust reverser upper locking actuator. \n\tThe Model 737-8 and -9 (737 MAX) airplane fleet is a young fleet and those airplanes have not been subjected to enough wear to warrant the use by any operator of the sensor target trimming procedure that leads to the upper locking actuator lock indication failure that may exist on 737 NG airplanes. The FAA therefore has determined that the integrity test is not necessary for the 737 MAX fleet. \n\nInterim Action \n\n\n\tThe FAA considers this AD interim action. The manufacturer is currently developing a modification that will address the unsafe condition identified in this AD. Once this modification is developed, approved, and available, the \n\n((Page 49006)) \n\nFAA might consider additional rulemaking. \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.) 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 seeking comment prior to the rulemaking. Similarly, 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 the flying public justifies forgoing notice and comment prior to adoption of this rule because alteration of thrust reverser upper locking actuators in accordance with certain unapproved AMM data could cause a thrust reverser upper locking actuator that is unlocked in flight to remain undetected, which could significantly increase the likelihood of an in- flight deployment of the thrust reverser and consequent loss of airplane control. 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. \n\tAccordingly, 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). In addition, for the reasons stated above, 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. \n\nComments Invited \n\n\n\tThis AD is a final rule that involves requirements affecting flight safety and was not preceded by notice and an opportunity for public comment. However, the 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-2019- 0696 and Product Identifier 2019-NM-136-AD at the beginning of your comments. The FAA specifically invites comments on the overall regulatory, economic, environmental, and energy aspects of this final rule. The FAA will consider all comments received by the closing date 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 http://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 \n\n\n\tThe requirements of the Regulatory Flexibility Act (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 2,149 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: \n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost on U.S. \n\tAction Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Integrity test (2,039 airplanes). 8 work-hours x $85$0 $680 per test cycle $1,386,520 per test \n\tper hour = $680 cycle. \n\tper test cycle. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tThe FAA has determined that revising the existing maintenance or inspection program takes an average of 90 work-hours per operator, although the agency recognizes that this number may vary from operator to operator. In the past, the FAA has estimated that this action takes 1 work-hour per airplane. Since operators incorporate maintenance or inspection program changes for their affected fleet(s), the FAA has determined that a per-operator estimate is more accurate than a per- airplane estimate. Therefore, the FAA estimates the total cost per operator to be $7,650 (90 work-hours x $85 per work-hour). \n\tThe FAA estimates the following costs to do any necessary replacement that would be required based on the results of the integrity test. The FAA has no way of determining the number of aircraft that might need this replacement: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Actuator replacement.......................... 8 work-hours x $85 per hour = $38,908 $39,588 \n\t$680. ---------------------------------------------------------------------------------------------------------------- \n\n\n\n((Page 49007)) \n\n\n\tAccording to the manufacturer, some or all of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected individuals. The FAA does not control warranty coverage for affected individuals. As a result, the FAA has included all known costsin the cost estimate. \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\tThis AD is issued in accordance with authority delegated by the Executive Director, Aircraft Certification Service, as authorized by FAA Order 8000.51C. In accordance with that order, issuance of ADs is normally a function of the Compliance and Airworthiness Division, but during this transition period, the Executive Director has delegated the authority to issue ADs applicable to transport category airplanes and associated appliances to the Director of the System Oversight Division. \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.