Background \n\n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2019-08-13, Amendment 39-19634 (84 FR 24007, May 24, 2019) (AD 2019-08-13). AD 2019-08-13 applied to Textron Aviation, Inc., Models 525, 525A, and 525B airplanes with Tamarack ATLAS winglets installed in accordance with STC SA03842NY. The NPRM published in the Federal Register on June 2, 2020 (85 FR 33583). \n\tAD 2019-08-13 prohibited all flight by revising the operating limitations in the airplane flight manual and fabricating and installing a placard, until a modification has been incorporated in accordance with an FAA-approved method. AD 2019-08-13 was based on MCAI originated by the European Union Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union. EASA issued AD No. 2019-0086-E, dated April 19, 2019, to address an unsafe condition related to reports of the ATLAS malfunctioning, which could lead to loss of control of the airplane. \n\tThe NPRM was prompted by EASA's revision to the MCAI. EASA issued AD No. 2019-0086R1, dated August 9, 2019, to require modifications previously developed by Cranfield Aerospace Solutions Limited (Cranfield), the holder of STC SA03842NY, to restore the safety of the ATLAS design and allow operators to reactivate the ATLAS. In the NPRM, the FAA proposed to require installing the modified Tamarack Active Camber Surface (TACS) control unit (TCU) and centering strips and revising the Tamarack maintenance manual supplement to include instructions for continued airworthiness relating to the centering strips. The FAA is issuing this AD to address the unsafe condition on these products. \n\tYou may obtain further information by examining the MCAI in the AD docket on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2019-0493. \n\nComments \n\n\n\tThe FAA received comments from two commenters. The commenters wereTamarack and the General Aviation Manufacturers Association (GAMA). The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nSupportive Comments \n\n\n\tTamarack and GAMA supported the NPRM. \n\nRequest To Revise the Preamble \n\n\n\tTamarack requested the FAA correct a statement in the preamble of the NPRM that the April 13, 2019 incident exposed a failure mode of the ATLAS that was not anticipated during certification. Tamarack commented this statement in the NPRM implies that only the worst case condition was tested while other less critical conditions were not. The commenter further stated that the failure mode that occurred on April 13, 2019 was tested during certification and shown to be recoverable. The commenter discussed the investigations and flights tests conducted by EASA and stated this data was reviewed and validated by the FAA before the FAA issued AD 2019-08-13. \n\tThe FAA partially agrees. The FAA issued AD 2019-08-13 on May 20, 2019. The FAA had received flight path data for the UK incident aircraft; however, this data did not provide any information about the operation of the ATLAS system during the incident. Therefore, it was not considered in the development of the FAA AD. No other information about the operation of the ATLAS system during this incident has been provided to the FAA. \n\tThe FAA received the root cause report mentioned by the commenter on April 22, 2019, which deemed further investigation was warranted to determine if the actions specified in Cranfield's service bulletin mitigated the unsafe condition. Many discussions between the FAA and EASA occurred before and after the issuance of AD 2019-08-13. Given that the Cranfield service bulletin did not contain adequate instructions for the use of ''speed tape'' to prevent the TACS from floating, the FAA found it unacceptable for correcting the unsafe condition. Instead of delaying action to address the unsafe condition to wait for testing of the ''speed tape,'' the FAA issued AD 2019-08-13 to ground the affected airplanes, knowing that operators could request an alternative method of compliance when substantiating data became available or when the investigation was complete. \n\tThe FAA did not make changes to this AD based on this comment. \n\n((Page 74597)) \n\nRequest To Update the STC Holder \n\n\n\tTamarack requested the FAA update the STC holder and contact information from Cranfield to Tamarack. The commenter noted that Cranfield finalized the transfer of STC SA03842NY to Tamarack after the issuance of AD 2019-08-13. \n\tThe FAA agrees and has updated the references as requested. \n\nConclusion \n\n\n\tThe FAA reviewed the relevant data, considered the comments received, and determined that air safety requires adopting the AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tThe FAA reviewed the following service documents required for compliance with this AD: \n\tCranfield Aerospace Solutions Limited Service Bulletin CAS/SB1480, Issue A, dated July 2019, which contains instructions to ensure installation of a modified TCU and the TACS centering strips; and \n\tTamarack Aerospace Group Cessna 525, 525A, & 525B ATLAS Winglet Maintenance Manual Supplement, Report Number: TAG-1100-0101, Issue G, dated September 3, 2019, which adds instructions to inspect the centering strips and adds repetitive inspection intervals to the Airworthiness Limitations section of the supplement for the centering strips. \n\tThis 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\nOther Related Service Information \n\n\n\tThe FAA also reviewed the following documents related to this AD: \n\tCranfield Aerospace Solutions Limited Service Bulletin CAS/SB1475, Issue A, dated February 2019,which contains the instructions for installing the centering strips to the TACS, identified as modification CAeM/Cessna/1475; \n\tTamarack Aerospace Group ATLAS Service Bulletin SBATLAS- 57-03, dated July 27, 2018, which contains instructions to remove the ATLAS TCU and return it to the ATLAS repair facility for modification; \n\tTamarack Aerospace Group ATLAS Service Bulletin SBATLAS- 57-05, dated February 20, 2019, which contains instructions to install centering strips on the TACS; and \n\tCranfield Aerospace Solutions Limited Service Bulletin CAS/SB1467, Issue B, dated July 2018, which contains instructions to remove the ATLAS TCU assembly and modify it as specified in CAS/SB1480, Issue A. \n\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD will affect 76 products of U.S. registry. The FAA also estimates that it will take 16 work-hours with a parts cost of $4,314 per product to modify the TCU, 24 work-hours with a parts cost of $199 per product to install the centering strips, and 1 work-hour per product to revise the limitations section as required by this AD. The average labor rate is $85 per work-hour. \n\tBased on these figures, the FAA estimates the cost of this AD on U.S. operators to be $607,848, or $7,998 per product. \n\tThe FAA has included all known costs in its cost estimate. According to the manufacturer, however, some of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected operators. \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 flightof 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 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.