Airworthiness Directives; Thommen Aircraft Equipment AG Digital Air Data Computers

[Federal Register Volume 90, Number 68 (Thursday, April 10, 2025)]
[Rules and Regulations]
[Pages 15304-15306]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-06066]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-2322; Project Identifier MCAI-2024-00065-Q; 
Amendment 39-23002; AD 2025-07-01]
RIN 2120-AA64


Airworthiness Directives; Thommen Aircraft Equipment AG Digital 
Air Data Computers

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain THOMMEN AIRCRAFT EQUIPMENT AG (THOMMEN) AC32 Digital Air Data 
Computers. This AD results from occurrences of AC32 Digital Air Data 
Computers (ADCs) that stop functioning below certain temperatures. This 
AD requires replacing an affected AC32 Digital ADC with a serviceable 
part. The FAA is issuing this AD to address the unsafe condition on 
these products.

DATES: This AD is effective May 15, 2025.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of May 15, 
2025.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2024-2322; 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:
    <bullet> For THOMMEN AIRCRAFT EQUIPMENT material identified 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.
    <bullet> 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. It is also available at regulations.gov under 
Docket No. FAA-2024-2322.

FOR FURTHER INFORMATION CONTACT: William Reisenauer, Aviation Safety 
Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; 
phone: (516) 228-7301; email: [email protected].

SUPPLEMENTARY INFORMATION:

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to certain THOMMEN AC32 
Digital Air Data Computers. The NPRM published in the Federal Register 
on September 30, 2024 (89 FR 79480). The NPRM was prompted by AD 2024-
0024, dated January 24, 2024, issued by the European Union Aviation 
Safety Agency (EASA), which is the Technical Agent for the Member 
States of the European Union (EASA AD 2024-0024) (also referred to as 
the MCAI). The MCAI states that there have been occurrences of certain 
AC32 Digital ADCs that stopped functioning at temperatures below-20 
degrees Celsius. The error is detectable and there is no transmission 
of 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.
    In the NPRM, the FAA proposed to require replacing an affected AC32 
Digital ADC with a serviceable part. The FAA is issuing this AD to 
address the unsafe condition on these products.
    You may examine the MCAI in the AD docket at regulations.gov under 
Docket No. FAA-2024-2322.

Discussion of Final Airworthiness Directive

Comments

    The FAA received one comment from an individual commenter and one 
comment from Bristow VTOL dba Era Helicopters. The following presents 
the comments received on the NPRM and the FAA's response to each 
comment.

Request To Revise the Applicability To Include Additional Helicopter 
Models

    An individual commenter stated that Columbia Helicopters, Inc. 
Model 107-II helicopters and Kawasaki Model 107-II helicopters also 
have configurations with the subject ADC installed. The FAA infers that 
the commenter requested that the applicability of the proposed AD be 
revised to include these additional helicopter models.
    Bristow VTOL dba Era Helicopters acknowledged that the proposed AD 
in paragraph ``(c)(2) Applicability'' mentions that ``Table 1 to 
paragraph (c)(2)'' does not limit the models identified in ``Table 1 to 
paragraph (c)(2)'' as being the only models that could have an affected 
serial number and affected part installed. However, the commenter 
stated that, while four Model AW189 helicopters are operating in the 
United States, only one helicopter serial number was identified as 
having an affected AC32 Digital ADC serial number and part number. The 
commenter confirmed that affected AC32 Digital ADC serial numbers and 
part numbers are not installed on any Model AW139 helicopter operating 
in the United States. Due to this

[[Page 15305]]

information, the commenter requested that the FAA include Model AW189 
helicopters in ``Table 1 to paragraph (c)(2).''
    Although, as stated in paragraph (c)(2) of the Applicability 
section of this AD, the aircraft models specified in Table 1 are not an 
exhaustive list of affected models, the FAA agrees with the commenters' 
requests. The FAA revised ``Table 1 to paragraph (c)(2)'' of this AD to 
include Columbia Helicopters, Inc. Model 107-II helicopters, Kawasaki 
Heavy Industries, Limited Model KV107-II helicopters, and Leonardo 
S.p.a. Model AW189 helicopters.

Conclusion

    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 reviewed the relevant data, 
considered the 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 
any changes described previously, this AD is adopted as proposed in the 
NPRM. None of the changes increase the economic burden on any operator.

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.

Costs of Compliance

    The FAA estimates that this AD affects 401 AC32 Digital ADCs that 
are installed on aircraft worldwide. The FAA has no way of determining 
how many of these ADCs are installed on aircraft of U.S. registry.
    The FAA estimates the following costs to comply with this 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.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                   Cost on U.S.
                Action                        Labor cost          Parts cost   Cost per product      operators
----------------------------------------------------------------------------------------------------------------
Replace affected AC32 Digital ADC....  12 work-hours x $85 per        $4,477              $5,497      $2,204,297
                                        hour = $1,020.
----------------------------------------------------------------------------------------------------------------

    The 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.

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

0
1. The authority citation for part 39 continues to read as follows:

    Authority:  49 U.S.C. 106(g), 40113, 44701.


Sec.  39.13   [Amended]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2025-07-01 Thommen Aircraft Equipment AG: Amendment 39-23002; Docket 
No. FAA-2024-2322; Project Identifier MCAI-2024-00065-Q.

(a) Effective Date

    This airworthiness directive (AD) is effective May 15, 2025.

(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.

[[Page 15306]]



         Table 1 to Paragraph (c)(2)--Applicable Aircraft Models
------------------------------------------------------------------------
        Type certificate holder                   Aircraft model
------------------------------------------------------------------------
Airbus Defense and Space S.A. (type      CN-235, CN-235-100, CN-235-200,
 certificate previously held by           and CN-235-300.
 Construcciones Aeronauticas, S.A.).
Airbus Helicopters.....................  AS332C, AS332C1, AS332L,
                                          AS332L1, AS3323L2.
Airbus Helicopters Deutschland GmbH      EC635T2+.
 (AHD).
Bell Textron Inc.......................  212, 412, and 412EP.
Bombardier Inc.........................  CL-600-1A11 (600).
Columbia Helicopters Inc...............  107-II, 234.
General Atomics Aerotek Systems GmbHl    228-100, 228-101, 228-200, 228-
 (type certificate formerly held by       201, 228-202, and 228-212.
 DORNIER LUFTFAHRT Inc.).
Gulfstream Aerospace LP................  Westwind Astra 1124 (serial
                                          numbers 004-0410).
International Air Response.............  C-130A.
Kawasaki Heavy Industries, Limited.....  KV107-II.
Leonardo S.p.a.........................  A109, A10A, A109A II, A109C,
                                          A109K2, A109S, 1099SP, AW139,
                                          and AW189.
Textron Aviation Inc...................  200, 300, 500, 501, 550, and
                                          551.
Viking Air Limited.....................  CL-215-6B11 (CL-215T Variant).
------------------------------------------------------------------------

    (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 that 
stopped 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 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].

    Issued on March 27, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2025-06066 Filed 4-9-25; 8:45 am]
BILLING CODE 4910-13-P

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