Discussion \n\n\n\tThe FAA published a Notice of Proposed Rulemaking (NPRM) in the Federal Register on January 23, 2020 (85 FR 3871), prompted by reports of two new unsafe conditions affecting CFM LEAP-1B model turbofan engines: (1) Increased fuel flow through certain fuel nozzles due to fuel nozzle coking, potentially causing distress to the static structures of the high-pressure turbine (HPT) and in-flight shutdown (IFSD) of one or more engines; and (2) the potential for undetected subsurface anomalies formed during the manufacturing process that could result in uncontained failure of the HPT stage 2 disk. \n\tThe NPRM also resulted from additional information related to two unsafe conditions previously addressed by AD 2018-25-09, Amendment 39- 19520 (83 FR 63559, December 11, 2018) (''AD 2018-25-09''), and AD 2019-12-01, Amendment 39-19656 (84 FR 28202, June 18, 2019) (''AD 2019- 12-01''), regarding: (1) Icing in the pressure sensor lines, potentially causing inaccurate pressure sensor readings and loss of thrust control; and (2) inadequate oil flow to the radial drive shaft (RDS) bearing, which can cause failure of the bearing and IFSD of one or more engines. AD 2018-25-09 applied to all CFM LEAP-1B21, -1B23, - 1B25, -1B27, -1B28, -1B28B1, -1B28B2, -1B28B2C, -1B28B3, -1B28BBJ1, and -1B28BBJ2 model turbofan engines. AD 2019-12-01 applied to CFM LEAP- 1B21, -1B23, -1B25, -1B27, -1B28, -1B28B1, -1B28B2, -1B28B3,-1B28B2C, - 1B28BBJ1, and -1B28BBJ2 model turbofan engines with certain RDS bearings installed. Thus, the FAA also proposed to supersede the two previously issued ADs addressing icing in the pressure sensor lines and inadequate oil flow to the RDS bearing. \n\tThe NPRM proposed to require revising the ALS of the applicable CFM LEAP-1B Engine Shop Manual and the operator's approved continuous airworthiness maintenance program to: (1) Add an ultrasonic inspection of the HPT stage 2 disk to detect subsurface anomalies formed during manufacturing; (2) add an inspection of the RDS bearing to address inadequate oil flow to the RDS bearing; (3) require monitoring and inspections of the fuel nozzle to address the potential distress to HPT static structures due to nozzle coking; and (4) update the electronic engine control (EEC) system software to address potential for icing in the pressure sensor lines. \n\tThe FAA is issuing this AD to address the unsafe conditions on these products. \n\nComments \n\n\n\tThe FAA gave the public the opportunity to participate in developing this AD. The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nRequest To Use CFM Diagnostics for Engine Monitoring To Detect Fuel Nozzle Coking \n\n\n\tA commenter asked whether CFM Diagnostics reporting is an acceptable method of compliance for CFM Service Bulletin (SB) LEAP-1B- 73-00-0030-01A-930A-D, Issue 001, dated January 8, 2020 (''SB 73- 0030''). The commenter stated that CFM Diagnostics has createda diagnostic report that includes the limits published in SB 73-0030. \n\tThe FAA agrees that use of CFM Diagnostics is an acceptable method of compliance for the engine monitoring in the ALS revisions required by this AD. This AD requires revising the ALS to include paragraph 6.B.(1) of CFM Engine Shop Manual (ESM) Data Module LEAP-1B-05-29-00- 01A-281B-C, Issue 001, dated January 9, 2020 (''ESM 05-29''), which requires either engine monitoring or repetitive borescope inspections specified in SB 73-0030 to detect fuel nozzle coking. Given that SB 73- 0030 recommends the use of CFM Diagnostics to perform engine monitoring, no change to this AD is necessary. \n\tThe commenter also asked whether switching between the engine monitoring and borescope inspection requirements is acceptable, because SB 73-0030 says that ''You must do the trend monitoring or BSI of the turbine hardware,'' which implies that only one of the two methods must be used. The commenter indicated that there may be scenarios when a data interruption occurs and they need to switch from engine condition monitoring to a borescope inspection. \n\tThe FAA agrees that switching between the engine monitoring and borescope inspection requirements is acceptable because the FAA has previously approved SB 73-0030, which allows operators to use either option. Based on the foregoing, no change to this AD is necessary. \n\nRequest for Credit for Inspections of Transfer Gearbox (TGB) Related to Inadequate Oil Flow to RDS Bearing \n\n\n\tA commenter requested that the AD provide credit for inspections of the TGB performed in accordance with CFM SB LEAP-1B-72-00-0222-01A- 930A-D, Issue 007, dated May 17, 2019 (''SB 72-0222''). The commenter indicated that, although the service bulletins refer to different maintenance manual tasks, both SB 72-0222 and CFM SB LEAP-1B-72-00- 0317-01A-930A-D, Issue 001, dated January 9, 2020 (''SB 72-0317''), require inspections meeting the same criteria. \n\tThe FAA agrees. This AD requires revising the ALS to include paragraph 6.B.(2) of ESM 05-29, which requires inspections of the RDS bearing as specified in SB 72-0317. SB 72-0317 provides the conditions for taking credit for inspections accomplished before the issuance of SB 72-0317, including inspections accomplished using SB 72-0222. Operators who meet the conditions specified in SB 72-0317 may take credit for previous inspections as part of their maintenance program. However, no change to this AD is necessary. Once an operator revises the ALS as required by this AD, the operator has fully complied with this AD. Compliance with the inspections remains mandatory as part of the ALS. \n\nSupport for the AD \n\n\n\tThe Boeing Company and the Air Line Pilots Association expressed support for the AD as written. \n\nNo Comments on the AD \n\n\n\tUnited Airlines Engineering commented that it reviewed the NPRM and had no comments. \n\nConclusion \n\n\n\tThe FAA reviewed the relevant data, considered the comments received, anddetermined that air safety and the \n\n((Page 14415)) \n\npublic interest require adopting this AD as proposed. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tThe FAA reviewed CFM ESM Data Module LEAP-1B-05-21-03-01A-281B-C, Issue 002, dated January 9, 2020 (''ESM 05-21''); and ESM 05-29. ESM 05-21 contains procedures for an ultrasonic inspection of the HPT stage 2 disk. ESM 05-29 contains procedures for inspection of the RDS bearing, monitoring and inspections of the fuel nozzle, and the required version of EEC system software. 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\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD affects 162 engines installed on airplanes of U.S. registry. \n\tThe 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 ---------------------------------------------------------------------------------------------------------------- Update ALS............................ 4 work-hours x $85 per $0 $340 $55,080 \n\thour = $340. TGB Screen Inspection................. 1 work-hour x 85 per 0 85 13,770 \n\thour = 85. HPT stage 2 Disk Inspection........... 6 work-hours x 85 per 0 510 82,620 \n\thour = 510. Fuel Nozzle Inspection................ 6 work-hours x 85 per 0 510 82,620 \n\thour = 510. Pressure Sub-system Software Upgrade.. 0.5 work-hours x 85 per 0 42.50 6,885 \n\thour = 42.50. RDS Borescope Inspection.............. 2 work-hours x85 per 0 170 27,540 \n\thour = 170. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tThe FAA estimates the following costs to do any necessary replacements that would be required based on the results of the inspection. The FAA has no way of determining the number of aircraft that might need these replacements: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- RDS Replacement............................... 200 work-hours x $85 per hour = $30,500 $47,500 \n\t$17,000. HPT stage 2 Disk Replacement.................. 1 work-hour x $85 per hour = $85 225,000225,085 Replace Set of Fuel Nozzles................... 40 work-hours x $85 per hour = 120,000 123,400 \n\t$3,400. ---------------------------------------------------------------------------------------------------------------- \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\tThe FAA has determined that this 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, \n\t(2) Will not affect intrastate aviation in Alaska, and \n\t(3) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.