AD 2025-20-01

This AD is effective November 6, 2025.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of November 6, 2025.

AD Docket: You may examine the AD docket at regulations.gov under Docket No. FAA-2025-1354; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this final rule, the mandatory continuing airworthiness information (MCAI), any comments received, and other information. The address for Docket Operations is U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.

Material Incorporated by Reference:

• For European Union Aviation Safety Agency (EASA) material identified in this AD, contact EASA, Konrad-Adenauer-Ufer 3, 50668 Cologne, Germany; telephone +49 221 8999 000; email ADs@easa.europa.eu. You may find this material on the EASA website at ad.easa.europa.eu.

• You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206-231-3195. It is also available at regulations.gov under Docket No. FAA-2025-1354.

Jonathan Duong, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: 516-228-7362; email: 9-AVS-AIR-BACO-COS@faa.gov.

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain ATR—GIE Avions de Transport Régional Model ATR42-500 and ATR72 airplanes. The NPRM was published in the Federal Register on July 7, 2025 (90 FR 29802). The NPRM was prompted by AD 2025-0004, dated January 7, 2025 (EASA AD 2025-0004) (also referred to as the MCAI), issued by EASA, which is the Technical Agent for the Member States of the European Union. The MCAI states that an ATR internal review of the TLU new avionics suite design identified an erroneous behavior of core processing module (CPM) 2, hosting the data concentration application (DCA) 2, that might affect the TLU command, monitoring, and indication. Further investigation results indicated that an erroneous monitoring of the TLU could occur when the airplane is flying above a certain speed due to the logic input from either ADC1 or ADC2 input.

In the NPRM, the FAA proposed to require modification of airplanes by installing one or two relays and associated wiring and testing of the TLU monitoring logic, as specified in EASA AD 2025-0004. The FAA is issuing this AD to address erroneous behavior of CPM 2, hosting the DCA 2, that could affect the TLU command, monitoring, and indication. This condition, if not corrected, could result in the rudder deflection not being limited at high airplane speed, which, if combined with a large rudder pedal input, could lead to the loss of control of the airplane.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2025-1354.

The FAA received a comment from the Air Line Pilots Association, International (ALPA) who supported the NPRM without change.

These products have been approved by the civil aviation authority of another country and are approved for operation in the United States. Pursuant to the FAA's bilateral agreement with this State of Design Authority, that authority has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator.

The FAA reviewed EASA AD 2025-0004, which specifies procedures for modifying airplanes by installing one or two relays and associated wiring. EASA AD 2025-0004 also specifies procedures for an operational test of the TLU monitoring logic after the modification, a functional test of the rudder travel limiter unit, and obtaining and following instructions to correct any failed test. For airplanes on which a previous revision of the applicable service information has been accomplished, EASA AD 2025-0004 specifies accomplishing “Additional Work,” which consists of a functional test of the rudder travel limiter unit. This material 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.

The FAA estimates that this AD affects 43 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD:

The FAA has received no definitive data on which to base the cost estimates for the on-condition actions specified in this AD.

The FAA has included all known costs in its cost estimate. According to the manufacturer, however, some or all of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected operators.

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.

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.

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:

1. The authority citation for part 39 continues to read as follows:

2. The FAA amends § 39.13 by adding the following new airworthiness directive: