[Federal Register Volume 89, Number 189 (Monday, September 30, 2024)]
[Proposed Rules]
[Pages 79480-79483]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-22251]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-2322; Project Identifier MCAI-2024-00065-Q]
RIN 2120-AA64


Airworthiness Directives; THOMMEN AIRCRAFT EQUIPMENT AG Digital 
Air Data Computers

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

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

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

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
    <bullet> Federal eRulemaking Portal: Go to regulations.gov. Follow 
the instructions for submitting comments.
    <bullet> Fax: (202) 493-2251.
    <bullet> Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE, Washington, DC 20590.
    <bullet> Hand Delivery: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    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 NPRM, the mandatory continuing airworthiness 
information (MCAI), any comments received, and other information. The 
street address for Docket Operations is listed above.
    Material Incorporated by Reference:
    <bullet> For THOMMEN AIRCRAFT EQUIPMENT material identified in this 
proposed AD, contact THOMMEN AIRCRAFT EQUIPMENT AG, Hofackerstrasse 48, 
4132 Muttenz, Switzerland; phone: +41 (0) 61 965 22 22; email: 
<a href="/cdn-cgi/l/email-protection#a2d1c3cec7d1e2d6cacdcfcfc7cc8cc3c7d0cd"><span class="__cf_email__" data-cfemail="2754464b425467534f484a4a42490946425548">[email protected]</span></a>; 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.

FOR FURTHER INFORMATION CONTACT: William Reisenauer, Aviation Safety 
Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; 
phone: (516) 228-7301; email: <a href="/cdn-cgi/l/email-protection#142d3955424739555d46395655575b39575b47547275753a737b62"><span class="__cf_email__" data-cfemail="536a7e1205007e121a017e1112101c7e101c00133532327d343c25">[email protected]</span></a>.

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

[[Page 79481]]

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.

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                    Cost per       Cost on U.S.
               Action                        Labor cost           Parts cost        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 
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

[[Page 79482]]

    (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.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

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

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:

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.

         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...............  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.
Leonardo S.p.a.........................  A109, A10A, A109A II, A109C,
                                          A109K2, A109S, 1099SP, and
                                          AW139.
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 
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: <a href="/cdn-cgi/l/email-protection#9cddd1d3dfdcfafdfdb2fbf3ea"><span class="__cf_email__" data-cfemail="b8f9f5f7fbf8ded9d996dfd7ce">[email protected]</span></a>. 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: <a href="/cdn-cgi/l/email-protection#4b72660a1d18660a021966090a0804660804180b2d2a2a652c243d"><span class="__cf_email__" data-cfemail="192034584f4a3458504b345b585a56345a564a597f7878377e766f">[email protected]</span></a>.

(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.

[[Page 79483]]

    (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: <a href="/cdn-cgi/l/email-protection#c1b2a0ada4b281b5a9aeacaca4afefa0a4b3ae"><span class="__cf_email__" data-cfemail="1665777a736556627e797b7b73783877736479">[email protected]</span></a>; 
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 <a href="/cdn-cgi/l/email-protection#b1d7c39fd8dfc2c1d4d2c5d8dedff1dfd0c3d09fd6dec7"><span class="__cf_email__" data-cfemail="0b6d79256265787b6e687f6264654b656a796a256c647d">[email protected]</span></a>.

    Issued on September 24, 2024.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2024-22251 Filed 9-27-24; 8:45 am]
BILLING CODE 4910-13-P


</pre><script data-cfasync="false" src="/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.js"></script></body>
</html>