Background The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to various airplanes modified with a certain configuration of the Garmin GFC 500 Autopilot System installed per STC No. SA01866WI. The NPRM published in the Federal Register on October 10, 2023 (88 FR 69891). The NPRM was prompted by a report of an un-commanded automatic pitch trim runaway when the autopilot was first engaged. In the NPRM, the FAA proposed to require updating the applicable Garmin GFC 500 Autopilot System software for your airplane and prohibit installing earlier versions of that software. The FAA issued a supplemental notice of proposed rulemaking (SNPRM) to amend 14 CFR part 39 by adding an AD that would apply to various airplanes modified with a certain configuration of the Garmin GFC 500 Autopilot System installed per STC No. SA01866WI. The SNPRM published in the Federal Register on April 17, 2024 (89 FR 27398). The SNPRM was prompted by comments received on the NPRM. The SNPRM proposed to revise the applicability by removing certain airplane models and adding other airplane models, revised paragraph (e) of the proposed AD to clarify that certain hardware failures affected the primary pitch servo and added Note 1 to paragraph (g) of the proposed AD. The FAA is issuing this AD to address autopilot software that does not properly handle certain hardware failures of the primary pitch servo. The unsafe condition, if not addressed, could result in un-commanded automatic pitch trim runaway and loss of control of the airplane. Discussion of Final Airworthiness Directive Comments The FAA received one comment from the National Transportation Safety Board (NTSB). The NTSB supported the SNPRM without change. Conclusion The FAA reviewed the relevant data, considered the comment 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. This AD is adopted as proposed in the SNPRM. Costs of Compliance The FAA estimates that this AD affects 5,900 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: Estimated Costs Action Labor cost Parts cost Cost per product Cost on U.S. operators Update autopilot software 1 work-hour × $85 per hour = $85 $0 $85 $501,500 Authority for This Rulemaking Title 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. The 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. Regulatory Findings 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. For the reasons discussed above, I certify that this AD: (1) Is not a "significant regulatory action" under Executive Order 12866, (2) Will not affect intrastate aviation in Alaska, and (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. List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. The Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: PART 39-AIRWORTHINESS DIRECTIVES 1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 [Amended] 2. The FAA amends § 39.13 by adding the following new airworthiness directive: 2024-14-03 Various Airplanes: Amendment 39-22784; Docket No. FAA-2023-1990; Project Identifier AD-2023-00734-A. (a) Effective Date This airworthiness directive (AD) is effective August 20, 2024. (b) Affected ADs None. (c) Applicability This AD applies to all airplane models specified in Table 1 to paragraph (c) of this AD, certificated in any category, having a Garmin GFC 500 Autopilot System that includes an optional GSA 28 pitch trim servo installed per Supplemental Type Certificate No. SA01866WI using Master Drawing List 005-01264-00, Revisions 1 through 76. BILLING CODE 4910-13-P Table 1 to Paragraph (c)-Applicable Airplane Models ER16JY24.018 ER16JY24.019 BILLING CODE 4910-13-C (d) Subject Joint Aircraft System Component (JASC) Code 2210, Autopilot System. (e) Unsafe Condition This AD was prompted by a report of an un-commanded automatic pitch trim runaway when the autopilot was first engaged. The FAA is issuing this AD to address autopilot software that does not properly handle certain hardware failures of the primary pitch servo. The unsafe condition, if not addressed, could result in un-commanded automatic pitch trim runaway and loss of control of the airplane. (f) Compliance Comply with this AD within the compliance times specified, unless already done. (g) Required Action Within 12 months after the effective date of this AD, update the Garmin GFC 500 Autopilot System software applicable to your airplane to a version that is not 8.01 or earlier for the G5, not version 9.01 or earlier for the G3X Touch, and not version 2.59 or earlier for the GI 275. Note 1 to paragraph (g): The software update can be done using Garmin Mandatory STC Service Bulletin 22123, Rev A, dated January 3, 2023. This AD also allows the installation of versions other than those listed in Garmin Mandatory STC Service Bulletin 22123, Rev A, dated January 3, 2023, provided those versions are not listed in paragraph (g) of this AD. (h) Installation Prohibition As of the effective date of this AD, do not install Garmin GFC 500 Autopilot System Software that is version 8.01 or earlier for the G5, version 9.01 or earlier for the G3X Touch, or version 2.59 or earlier for the GI 275, on any airplane. (i) Alternative Methods of Compliance (AMOCs) (1) The Manager, Central Certification Branch, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the Central Certification Branch, send it to the attention of the person identified in paragraph (j)(1) of this AD. Information may be emailed to wichita-cos@faa.gov. (2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office. (j) Additional Information (1) For more information about this AD, contact Christopher Withers, Aviation Safety Engineer, FAA, 1801 S Airport Road, Wichita, KS 67209; phone: (316) 946-4190; email: christopher.d.withers@faa.gov. (2) For material identified in this AD that is not incorporated by reference, contact Garmin International, Attention: Garmin Aviation Support, 1200 E 151st Street, Olathe, KS 66062; phone: (866) 739-5687; website: support.garmin.com/en-US/aviation/. (k) Material Incorporated by Reference None. Issued on July 10, 2024. James D. Foltz, Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.