Airworthiness Directives; Fiberglas-Technik Rudolf Lindner GmbH & Co. KG (Type Certificate Previously Held by GROB Aircraft AG, Grob Aerospace GmbH i.l., Grob Aerospace GmbH, Burkhart Grob Luft- und Raumfahrt GmbH & Co. KG) Gliders

[Federal Register Volume 90, Number 189 (Thursday, October 2, 2025)]
[Rules and Regulations]
[Pages 47540-47544]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-19355]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2025-3421; Project Identifier MCAI-2025-01202-G; 
Amendment 39-23160; AD 2025-20-07]
RIN 2120-AA64


Airworthiness Directives; Fiberglas-Technik Rudolf Lindner GmbH & 
Co. KG (Type Certificate Previously Held by GROB Aircraft AG, Grob 
Aerospace GmbH i.l., Grob Aerospace GmbH, Burkhart Grob Luft- und 
Raumfahrt GmbH & Co. KG) Gliders

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule; request for comments.

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

SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all 
Fiberglas-Technik Rudolf Lindner GmbH & Co. KG Model G103 TWIN II, 
G103A TWIN II ACRO, G103C TWIN III ACRO, and G 103 C TWIN III SL 
gliders. This AD was prompted by a report of corrosion on the inner 
sides of the welded steel rudder drive plate. This AD requires 
repetitive inspections and a one-time detailed inspection of the rudder 
drive plate for corrosion and water entry and a modification of the 
rudder drive plate to improve corrosion protection, as applicable. This 
AD also requires replacement of the rudder if corrosion is found during 
the inspections that exceed light surface rust. This AD also requires 
applying additional sealing to the rudder drive plate, which 
constitutes terminating action for the repetitive inspections. The

[[Page 47541]]

FAA is issuing this AD to address the unsafe condition on these 
products.

DATES: This AD is effective October 17, 2025.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of October 17, 
2025.
    The FAA must receive comments on this AD by November 17, 2025.

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-2025-3421; 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 
street address for Docket Operations is listed above.
    Material Incorporated by Reference:
    <bullet> For Fiberglas-Technik Rudolf Lindner material identified 
in this AD, contact Fiberglas-Technik Rudolf Lindner GmbH & Co. KG, 
Steige 3 Walpertshofen, Germany; phone: +49 (0) 7353 22 43; email: 
Lindner.com">info@LTB-Lindner.com; website: ltb-lindner.com.
    <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-2025-3421.

FOR FURTHER INFORMATION CONTACT: Adam Hein, Aviation Safety Engineer, 
FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (316) 
946-4116; email: [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites you to send any written data, views, or arguments 
about this final rule. Send your comments using a method listed under 
the ADDRESSES section. Include ``Docket No. FAA-2025-3421; Project 
Identifier MCAI-2025-01202-G'' at the beginning of your comments. The 
most helpful comments reference a specific portion of the final rule, 
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 final rule 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 final rule.

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 AD 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 AD, 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 AD. Submissions containing CBI should be sent to Adam 
Hein, 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 2025-0140, dated July 7, 2025 (referred to as ``the MCAI''), to 
correct an unsafe condition on all Fiberglas-Technik Rudolf Lindner 
GmbH & Co. KG Model G103 TWIN II, G103A TWIN II ACRO, G103C TWIN III, 
G103C TWIN III ACRO, and G 103 C TWIN III SL sailplanes (gliders).
    The MCAI states that corrosion was found on the inner sides of the 
welded drive plate during a teardown inspection of a rudder. This 
condition, if not detected and corrected, could affect the structural 
integrity of the rudder drive plate, which could lead to reduced 
control or loss of control of the glider. The MCAI requires repetitive 
inspections of the rudder drive plate for corrosion and possible water 
entry and a one-time detailed inspection and modification of the rudder 
drive plate either immediately or at the next service life extension 
inspection, depending on the results of the inspection. The MCAI also 
requires replacement of the rudder assembly if corrosion is found 
during the inspections that exceed light surface rust. The MCAI also 
requires applying additional sealing to the rudder drive plate, which 
constitutes terminating action for the repetitive inspections.
    You may examine the MCAI in the AD docket at regulations.gov under 
Docket No. FAA-2025-3421.

Material Incorporated by Reference Under 1 CFR Part 51

    The FAA reviewed Fiberglas-Technik Rudolf Lindner Service Bulletin 
SB-G10, Revision 1, dated February 27, 2025. This material specifies 
procedures for inspecting the rudder drive plate for corrosion and 
water entry, modifying the rudder drive plate to improve corrosion 
protection, applying additional sealing, and replacing the rudder. This 
material contains German to English translation.
    The European Union Aviation Safety Agency (EASA) used the English 
translation in referencing the document. For enforceability purposes, 
the FAA will refer to the Fiberglas-Technik Rudolf Lindner service 
material in English as it appears on the document.
    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 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 is issuing this AD 
after determining that the unsafe condition described previously is 
likely to exist or develop on other products of the same type design.

AD Requirements

    This AD requires accomplishing the actions specified in the 
material already described, except as discussed under ``Differences 
Between this AD and the Service Material and MCAI.''

[[Page 47542]]

Differences Between This AD and the Service Material and MCAI

    While the MCAI applies to Fiberglas-Technik Rudolf Lindner GmbH & 
Co. KG Model G103C TWIN III gliders, this AD does not because this 
model does not have an FAA type certificate.
    Fiberglas-Technik Rudolf Lindner Service Bulletin SB-G10, Revision 
1, dated February 27, 2025, requires replacing the rudder or contacting 
the manufacturer for approved instructions if corrosion exceeding light 
surface rust is detected. This AD requires replacing the rudder or 
contacting either the Manager, International Validation Branch, FAA; or 
EASA; or Fiberglas-Technik Rudolf Lindner GmbH & Co. KG's EASA Design 
Organization Approval (DOA) for approved instructions if corrosion 
exceeding light surface rust is detected. If approved by the DOA, the 
approval must include the DOA-authorized signature.

Justification for Immediate Adoption and Determination of the Effective 
Date

    Section 553(b) of the Administrative Procedure Act (APA) (5 U.S.C. 
551 et seq.) authorizes agencies to dispense with notice and comment 
procedures for rules when the agency, for ``good cause,'' finds that 
those procedures are ``impracticable, unnecessary, or contrary to the 
public interest.'' Under this section, an agency, upon finding good 
cause, may issue a final rule without providing notice and seeking 
comment prior to issuance. Further, section 553(d) of the APA 
authorizes agencies to make rules effective in less than thirty days, 
upon a finding of good cause.
    An unsafe condition exists that requires the immediate adoption of 
this AD without providing an opportunity for public comments prior to 
adoption. The FAA has found that the risk to the flying public 
justifies forgoing notice and comment prior to adoption of this rule 
because corrosion on the inner sides of the welded steel rudder drive 
plate could affect the structural integrity of the rudder drive plate 
and lead to reduced control or loss of control of the glider. 
Additionally, the glider fleet has an average age of 5,400 flight 
hours, and due to limitations in general aviation reporting, the exact 
age of each glider is unknown. Based on the fleet's age distribution 
and an average of 10 hours time-in-service (TIS) per month, it is 
estimated that certain gliders will require the one-time inspection and 
modification within 50 hours TIS or 3 months, whichever occurs first, 
which is shorter than the time necessary for the public to comment and 
for publication of the final rule. Accordingly, notice and opportunity 
for prior public comment are impracticable and contrary to the public 
interest pursuant to 5 U.S.C. 553(b).
    In addition, the FAA finds that good cause exists pursuant to 5 
U.S.C. 553(d) for making this amendment effective in less than 30 days, 
for the same reasons the FAA found good cause to forgo notice and 
comment.

Regulatory Flexibility Act

    The requirements of the Regulatory Flexibility Act (RFA) do not 
apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt 
a rule without prior notice and comment. Because the FAA has determined 
that it has good cause to adopt this rule without prior notice and 
comment, RFA analysis is not required.

Costs of Compliance

    The FAA estimates that this AD affects 68 gliders of U.S. registry.
    The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                            Parts                               Cost on U.S.
              Action                      Labor cost         cost      Cost per product          operators
----------------------------------------------------------------------------------------------------------------
Inspect rudder drive plate........  1 work-hour x $85 per       $0  $85 per inspection     $5,780 per inspection
                                     hour = $85 per                  cycle.                 cycle.
                                     inspection cycle.
Detailed inspection of rudder       4 work-hours x $85           0  $340.................  $23,120.
 drive plate.                        per hour = $340.
Apply sealing.....................  1 work-hour x $85 per        0  $85..................  $5,780.
                                     hour = $85.
Re-install rudder.................  1 work-hour x $85 per        0  $85..................  $5,780.
                                     hour = $85.
----------------------------------------------------------------------------------------------------------------

    The FAA estimates the following costs to do any necessary 
modification or replacement of the rudder that would be required based 
on the results of the inspection. The agency has no way of determining 
the number of gliders that might need the modification or replacement.

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Replace rudder................................  2 work-hours x $85 per hour =             $6,582          $6,752
                                                 $170.
----------------------------------------------------------------------------------------------------------------

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

[[Page 47543]]

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, and
    (2) Will not affect intrastate aviation in Alaska.

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:

2025-20-07 Fiberglas-Technik Rudolf Lindner GmbH & Co. KG (type 
certificate previously held by GROB Aircraft AG, Grob Aerospace GmbH 
i.l., Grob Aerospace GmbH, Burkhart Grob Luft- und Raumfahrt GmbH & 
Co. KG): Amendment 39-23160; Docket No. FAA-2025-3421; Project 
Identifier MCAI-2025-01202-G.

(a) Effective Date

    This airworthiness directive (AD) is effective October 17, 2025.

 (b) Affected ADs

    None.

(c) Applicability

    This AD applies to Fiberglas-Technik Rudolf Lindner GmbH & Co. 
KG (type certificate previously held by GROB Aircraft AG, Grob 
Aerospace GmbH i.l., Grob Aerospace GmbH, Burkhart Grob Luft- und 
Raumfahrt GmbH & Co. KG) Model G103 TWIN II, G103A TWIN II ACRO, 
G103C TWIN III ACRO, and G 103 C TWIN III SL gliders, certificated 
in any category.

(d) Subject

    Joint Aircraft System Component (JASC) Code 2720, Rudder Control 
System.

(e) Unsafe Condition

    This AD was prompted by a report of corrosion on the inner sides 
of the welded steel rudder drive plate. The FAA is issuing this AD 
to detect and address corrosion and water entry in the rudder drive 
plate. The unsafe condition, if not detected and corrected, could 
affect the structural integrity of the rudder drive plate, which 
could lead to reduced control or loss of control of the glider.

(f) Compliance

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

(g) Definition

    For the purpose of this AD, a ``serviceable rudder'' is a rudder 
which has accumulated zero hours time-in-service (TIS), or a rudder 
that has been inspected and modified, as necessary, in accordance 
with paragraphs (h)(1) and (2) of this AD and is found to be crack 
and corrosion free.

(h) Required Actions

    (1) Within 50 hours TIS or 3 months, whichever occurs first 
after the effective date of this AD, and, thereafter, at intervals 
not to exceed every 12 months, inspect the rudder drive plate for 
evidence of corrosion or water entry in accordance with the Actions 
and Instructions, section A, of Fiberglas-Technik Rudolf Lindner 
Service Bulletin SB-G10, Revision 1, dated February 27, 2025.
    (2) Perform a one-time detailed inspection of the rudder drive 
plate in accordance with the Actions and Instructions, section B, 
steps 1 and 2 of Fiberglas-Technik Rudolf Lindner Service Bulletin 
SB-G10, Revision 1, dated February 27, 2025, at whichever compliance 
time in paragraphs (h)(2)(i) or (ii) of this AD occurs first.
    (i) Before further flight if during any inspection as required 
by paragraph (h)(1) of this AD, evidence of corrosion or water 
ingress is found; or
    (ii) At the next service life extension inspection that occurs 
after the effective date of this AD.
    (3) If, as a result of the inspection required by paragraph 
(h)(2) of this AD, corrosion of the rudder drive plate is detected 
that exceeds light surface rust and cannot be removed using steel 
wool, before further flight, replace the rudder with a serviceable 
rudder, or contact the Manager, International Validation Branch, 
FAA; or EASA; or Fiberglas-Technik Rudolf Lindner GmbH & Co. KG EASA 
Design Organization Approval (DOA) for approved instructions. If 
approved by the DOA, the approval must include the DOA-authorized 
signature.
    (4) If the rudder is replaced with a serviceable rudder, before 
further flight, apply additional sealing to the rudder drive plate 
in accordance with the Actions and Instructions, Section C, of 
Fiberglas-Technik Rudolf Lindner Service Bulletin SB-G10, Revision 
1, dated February 27, 2025.
    (5) If, as a result of the inspection required by paragraph 
(h)(2) of this AD, light surface rust is detected, before further 
flight, modify the rudder drive plate in accordance with the Actions 
and Instructions, section B, steps 4 through 7 of Fiberglas-Technik 
Rudolf Lindner Service Bulletin SB-G10, Revision 1, dated February 
27, 2025.
    (6) If, as a result of the inspection required by paragraph 
(h)(2) of this AD, no evidence of corrosion or water ingress is 
detected, before further flight, modify the rudder drive plate in 
accordance with the Actions and Instructions, section B, steps 5 
through 7 of Fiberglas-Technik Rudolf Lindner Service Bulletin SB-
G10, Revision 1, dated February 27, 2025.
    (7) Following completion of the modification of the rudder drive 
plate required by paragraph (h)(5) or (h)(6) of this AD, before 
further flight, apply additional sealing to the rudder drive plate 
in accordance with the Actions and Instructions, Section C, of 
Fiberglas-Technik Rudolf Lindner Service Bulletin SB-G10, Revision 
1, dated February 27, 2025.
    (8) Following completion of the sealing application required by 
paragraph (h)(7) of this AD, re-install the rudder in accordance 
with the Actions and Instructions, Section D, of Fiberglas-Technik 
Rudolf Lindner Service Bulletin SB-G10, Revision 1, dated February 
27, 2025.
    (9) Application of additional sealing to the rudder drive plate, 
as required by paragraphs (h)(4) and (h)(7) of this AD, constitutes 
terminating action for the repetitive inspections required by 
paragraph (h)(1) of this AD for that glider.

(i) Alternative Methods of Compliance (AMOCs)

    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 manager of the International Validation Branch, send 
it to the attention of the person identified in paragraph (j) 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 local flight standards district 
office/certificate holding district office.

(j) Additional Information

    For more information about this AD, contact Adam Hein, Aviation 
Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 
11590; phone: (316) 946-4116; email: [email protected].

(k) 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) Fiberglas-Technik Rudolf Lindner Service Bulletin SB-G10, 
Revision 1, dated February 27, 2025.
    Note 1 to paragraph (k)(2)(i): This material contains German to 
English translation. The European Union Aviation Safety Agency 
(EASA) used the English translation in referencing the document. For 
enforceability purposes, the FAA will refer to the Fiberglas-Technik 
Rudolf Lindner service material in English as it appears on the 
document.
    (ii) [Reserved]
    (3) For Fiberglas-Technik Rudolf Lindner material identified in 
this AD, contact Fiberglas-Technik Rudolf Lindner GmbH & Co. KG, 
Steige 3 Walpertshofen, Germany;

[[Page 47544]]

phone: +49 (0) 7353 22 43; email: Lindner.com">info@LTB-Lindner.com; website: 
ltb-lindner.com.
    (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 September 30, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2025-19355 Filed 9-30-25; 4:15 pm]
BILLING CODE 4910-13-P

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