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

<RULE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 39</CFR> <DEPDOC>[Docket No. FAA-2025-3421; Project Identifier MCAI-2025-01202-G; Amendment 39-23160; AD 2025-20-07]</DEPDOC> <RIN>RIN 2120-AA64</RIN> <SUBJECT>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</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), DOT. <HD SOURCE="HED">ACTION:</HD> Final rule; request for comments. <SUM> <HD SOURCE="HED">SUMMARY:</HD> 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 FAA is issuing this AD to address the unsafe condition on these products. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> 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. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods: • <E T="03">Federal eRulemaking Portal:</E> Go to <E T="03">regulations.gov</E> . Follow the instructions for submitting comments. • <E T="03">Fax:</E> (202) 493-2251. • <E T="03">Mail:</E> U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590. • <E T="03">Hand Delivery:</E> Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. <E T="03">AD Docket:</E> You may examine the AD docket at <E T="03">regulations.gov</E> 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. <E T="03">Material Incorporated by Reference:</E> • 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: <E T="03">info@LTB-Lindner.com;</E> website: <E T="03">ltb-lindner.com.</E> • 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 <E T="03">regulations.gov</E> under Docket No. FAA-2025-3421. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Adam Hein, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (316) 946-4116; email: <E T="03">adam.hein@faa.gov</E> . </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Comments Invited</HD> 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 <E T="02">ADDRESSES</E> 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 <E T="03">regulations.gov,</E> including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this final rule. <HD SOURCE="HD1">Confidential Business Information</HD> 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. <HD SOURCE="HD1">Background</HD> 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 <E T="03">regulations.gov</E> under Docket No. FAA-2025-3421. <HD SOURCE="HD1">Material Incorporated by Reference Under 1 CFR Part 51</HD> 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 <E T="02">ADDRESSES</E> section. <HD SOURCE="HD1">FAA's Determination</HD> 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. <HD SOURCE="HD1">AD Requirements</HD> 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.” <HD SOURCE="HD1">Differences Between This AD and the Service Material and MCAI</HD> 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 s ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 25k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━