Airworthiness Directives: Thommen Aircraft Equipment AG Digital Air Data Computers

Airworthiness Directives; THOMMEN AIRCRAFT EQUIPMENT AG Digital Air Data Computers

Dates

The FAA must receive comments on this NPRM by November 14, 2024.

Supplementary Information

Comments Invited

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under ADDRESSES . Include "Docket No. FAA-2024-2322; Project Identifier MCAI-2024-00065-Q" at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this proposal because of those comments.

Except 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 regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.

Confidential Business Information

CBI 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 NPRM 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 NPRM, 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 NPRM. Submissions containing CBI should be sent to William Reisenauer, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.

Background

The European Union Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2024-0024, dated January 24, 2024 (also referred to as the MCAI), to correct an unsafe condition on certain THOMMEN AC32 Digital ADCs. The MCAI states that there have been occurrences of certain AC32 Digital ADCs stopping functioning at temperatures below −20 degrees Celsius. The error is detectable and does not transmit erroneous data. The problem is caused by the power module and the affected units have been identified. This condition, if not addressed, could result in insufficient navigational data provided to the flight crew, resulting in reduced control of the aircraft. The MCAI requires removing from service each affected part and specifies that only serviceable parts as defined in the MCAI may be installed.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2024-2322.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed THOMMEN AIRCRAFT EQUIPMENT Service Bulletin SB AC32/07, Revision 1.0, dated August 31, 2023 (THOMMEN SB AC32/07, Revision 1.0). This material specifies procedures for determining if an aircraft is equipped with an affected AC32 Digital ADC listed in Appendix A, determining if the actions specified in THOMMEN SB AC32/07, Revision 1.0, were already accomplished, and replacing any affected THOMMEN AC32 Digital ADC.

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.

FAA's Determination

These products have been approved by the 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, it has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.

Proposed AD Requirements in This NPRM

This proposed AD would require replacing affected AC32 Digital ADCs with serviceable parts. This proposed AD would also prohibit the installation of an affected AC32 Digital ADC on any aircraft.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 401 AC32 Digital ADCs that are installed on aircraft worldwide. The FAA has no way of determining how many of these ADC are installed on aircraft of U.S. registry.

The FAA estimates the following costs to comply with this proposed AD. These costs assume all 401 AC32 Digital ADCs are installed on aircraft of U.S. registry. The FAA expects a portion of the affected population to exist outside of the U.S. and the estimated costs to be lower.

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

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

The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would 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 this proposed regulation:

(1) Is not a "significant regulatory action" under Executive Order 12866,

(2) Would not affect intrastate aviation in Alaska, and

(3) Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

The Proposed Amendment

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

Part 39 Airworthiness Directives

Thommen Aircraft Equipment AG: Docket No. FAA-2024-2322; Project Identifier MCAI-2024-00065-Q.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by November 14, 2024.

(b) Affected ADs

None.

(c) Applicability

(1) This AD applies to THOMMEN AIRCRAFT EQUIPMENT AG (THOMMEN) AC32 Digital Air Data Computers (ADCs) having an affected part as defined in paragraph (f)(1) of this AD.

(2) This appliance is installed on, but not limited to, the following aircraft models specified in Table 1 to paragraph (c)(2) of this AD, certificated in any category.

(3) This appliance is approved for installation and could be installed on various aircraft modified by Supplemental Type Certificate (STC) No. SR09595RC or ST01523WI.

(d) Subject

Joint Aircraft System Component (JASC) Code 3417, Air Data Computer.

(e) Unsafe Condition

This AD was prompted by occurrences of AC32 Digital ADCs stopping functioning due to the power module failing at temperatures below -20 degrees Celsius. The unsafe condition, if not addressed, could result in insufficient navigational data provided to the flight crew, resulting in reduced control of the aircraft.

(f) Definitions

For the purpose of this AD the definitions in paragraphs (f)(1) through (4) of this AD apply:

(1) Affected part: THOMMEN AC32 Digital ADCs, part numbers (P/N) AC32.10.21.10.XX, AC32.10.21.11.XX, AC32.11.21.10.XX, and AC32.11.21.11.XX (where XX represents any alpha/numerical sequence), and having a serial number (S/N) listed in Appendix A of THOMMEN AIRCRAFT EQUIPMENT Service Bulletin SB AC32/07, Revision 1.0, dated August 31, 2023 (THOMMEN SB AC32/07 Revision 1.0).

(2) Serviceable part: Any AC32.(X) Digital ADC that is not an affected part; or an affected part where the power module has been replaced by THOMMEN, in accordance with the instructions of THOMMEN SB AC32/07 Revision 1.0.

(3) Group 1 aircraft: Have an affected part installed.

(4) Group 2 aircraft: Do not have an affected part installed but are eligible for AC32.(X) Digital ADC installation.

(g) Compliance

Comply with this AD within the compliance times specified, unless already done.

(h) Required Actions

For Group 1 aircraft: Within 12 months after the effective date of this AD, remove each affected part from service and replace it with a serviceable part in accordance with paragraph 3.A. of the Accomplishment Instructions in THOMMEN SB AC32/07 Revision 1.0, except where this material specifies to send the removed affected part to the manufacturer, this AD does not require that action.

(i) Parts Installation Prohibition

For Group 1 and 2 aircraft: As of the effective date of this AD, do not install an affected part on any aircraft.

(j) Special Flight Permits

A one-time special flight permit may be issued in accordance with 14 CFR 21.197 and 21.199 in order to fly to a maintenance base to perform the required action in this AD, provided a flight profile above −15 degrees Celsius (5 degrees Fahrenheit) is maintained.

(k) Alternative Methods of Compliance (AMOCs)

(1) The Manager, International Validation 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 International Validation Branch, send it to the attention of the person identified in paragraph (l) of this AD and email to: [email protected]. Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the responsible Flight Standards Office.

(l) Additional Information

For more information about this AD, contact William Reisenauer, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (516) 228-7301; email: [email protected].

(m) Material Incorporated by Reference

(1) The Director of the Federal Register approved the incorporation by reference (IBR) of the material listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.

(2) You must use this material as applicable to do the actions required by this AD, unless the AD specifies otherwise.

(i) THOMMEN AIRCRAFT EQUIPMENT Service Bulletin SB AC32/07, Revision 1.0, dated August 31, 2023.

(ii) [Reserved]

(3) For THOMMEN AIRCRAFT EQUIPMENT material in this AD, contact THOMMEN AIRCRAFT EQUIPMENT AG, Hofackerstrasse 48, 4132 Muttenz, Switzerland; phone: +41 (0) 61 965 22 22; email: [email protected]; website: thommen.aero.

(4) You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 901 Locust, Kansas City, MO 64106. For information on the availability of this material at the FAA, call (817) 222-5110.

(5) You may view this material at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected].