DG Aviation DG-1000M Glider Airworthiness Directive - Engine Mount Cracking

Content

ACTION:

Final rule; request for comments.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) for all DG Aviation GmbH (Type Certificate Previously Held by DG Flugzeugbau
GmbH) Model DG-1000M gliders. This AD was prompted by reports of engine mount cracking near the propeller head. This AD requires
updating the maintenance manual, inspecting the engine mount for cracks, and taking corrective actions if cracks are found.
This AD also requires performing a powerplant belt tension inspection and, depending on the results of the inspection, adjusting
the belt tension. This AD also requires balancing the propeller assembly and installing a carbon fiber reinforced plastic
(CFRP) bracket. This AD also prohibits accomplishing certain maintenance actions in the maintenance manual. The FAA is issuing
this AD to address the unsafe condition on these products.

DATES:

This AD is effective April 20, 2026.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as
of April 20, 2026.

The FAA must receive comments on this AD by May 18, 2026.

ADDRESSES:

You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods:

• Federal eRulemaking Portal: Go to regulations.gov. Follow the instructions for submitting comments.

• Fax: (202) 493-2251.

• 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.

• 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-2026-2727; 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:

• For DG Aviation GmbH material identified in this AD, contact DG Aviation GmbH, Rita Rodrigues, Otto Lilienthal Weg 2/Am
Flugplatz, Bruchsal, Germany; phone: +49 (0) 7251 36660-32; email: rodrigues@dg-aviation.de; website: dg-aviation.de/en/dg-flugzeugbau/contact.

• 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-2026-2727.

FOR FURTHER INFORMATION CONTACT:

For more information about this AD, contact Evan Weaver, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury,
NY 11590; phone: (316) 944-8910; email: evan.p.weaver@faa.gov.

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-2026-2727; Project Identifier MCAI-2025-00685-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 Evan Weaver,
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 2025-0091, dated April 23, 2025 (EASA AD 2025-0091) (also referred to as the MCAI), to correct an unsafe
condition on DG Aviation GmbH Model DG-1000M gliders. The MCAI states that occurrences of engine mount cracking near the propeller
head on DG-1000M powered gliders have been reported. Given the urgency of the unsafe condition, EASA issued the MCAI as a
final rule with request for comments. To address this potential unsafe condition, DG Aviation GmbH issued DG Aviation GmbH
Technical Note No. TN 1000/51, Doc. No. TM1000-51 FE-29-01, Issue 01.d, dated February 26, 2025 (DG Aviation GmbH TN TM1000-51
FE-29-01, Issue 01.d), to provide inspection, repair, and modification instructions for affected parts. This condition, if
not addressed, could result in loss of power transmission to the propeller and reduced or loss of control of the glider.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2026-2727.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed DG Aviation GmbH TN TM1000-51 FE-29-01, Issue 01.d. This material specifies procedures for updating the maintenance
manual, inspecting the engine mount for cracks, repairing the engine mount, performing a powerplant belt tension inspection
and adjustment, installing a CFRP bracket, balancing the propeller assembly, and updating the software in the front and rear
cockpit DEI-NTs and the control unit NT (E-box).

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 and material 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 Proposed AD and the Referenced Material.”

Differences Between This Proposed AD and the Referenced Material

Paragraph 1 of the Instructions section of DG Aviation GmbH TN TM1000-51 FE-29-01, Issue 01.d, provides instructions to “Exchange
the following Maintenance manual pages against new pages: 0.0, 0.2, 0.3, 0.5, 0.7, 0.13, 4.2, 4.19, 6.1, 6.2, diagram 21 issued
January 2025, marked with TN1000-51. Respect the marked changes.” This AD, instead, requires revising page 0.13 in accordance
with paragraph 1 of the Instructions section of DG Aviation GmbH TN TM1000-51 FE-29-01, Issue 01.d, dated February 26, 2025.

Paragraph 2 of the Instructions section of DG Aviation GmbH TN TM1000-51 FE-29-01, Issue 01.d, provides instructions to contact
DG Aviation GmbH to obtain an approved repair and accomplish that repair accordingly, including post-repair follow-on action(s),
as applicable. This AD instead requires contacting either the Manager, International Validation Branch, FAA; EASA; or DG Aviation
GmbH's EASA Design Organization Approval (DOA); for approved repair instructions and, within the compliance time specified
therein, accomplish those instructions accordingly, including post-repair follow-on action(s), as applicable. If approved
by the DOA, the approval must include the DOA-authorized signature.

Although paragraph 6 of the Instructions section of DG Aviation GmbH TN TM1000-51 FE-29-01, Issue 01.d, provides instructions
to send both front and rear cockpit DEI-NTs as well as the control unit-NT (E-box) to DG Aviation for software updates, this
AD does not require those actions.

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 cracking of the engine mount near the propeller head could lead to structural failure of the engine mount
with consequent loss of power transmission to the propeller, and reduced or loss of control of the glider. Therefore, an inspection
of the engine mount for cracks and a power plant belt tension inspection are required before further flight, or within 30
days of the effective date of this AD, whichever occurs first. In addition, repair of the engine mount is required before
further flight if cracks are found during inspection. These compliance times are 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 two gliders of U.S. registry.

The FAA estimates the following costs to comply with this AD:

| Action | Labor cost | Parts cost | Cost per
product | Cost on U.S.
operators |
| --- | --- | --- | --- | --- |
| Update maintenance manual | 1 work-hour × $85 per hour = $85 | $0 | $85 | $170 |
| Inspect engine mount | 1 work-hour × $85 per hour = $85 | 0 | 85 | 170 |
| Accomplish powerplant belt tension inspection | 1 work-hour × $85 per hour = $85 | 0 | 85 | 170 |
| Install CFRP bracket | 2 work-hours × $85 per hour = $170 | 0 | 170 | 340 |
| Perform dynamic balancing of the propeller assembly | 2 work-hours × $85 per hour = $170 | 0 | 170 | 340 |
The FAA estimates the following costs to do any repairs or replacements 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 these repairs or replacements.

| Action | Labor cost | Parts cost | Cost per
product |
| --- | --- | --- | --- |
| Repair engine mount | 4 work-hours × $85 per hour = $340 | $0 | $340 |
| Adjust belt tension | 2 work-hours × $85 per hour = $170 | 0 | 170 |
| Replace engine mount | 4 work-hours × $85 per hour = $340 | 0 | 340 |

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, 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

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

Authority:

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

§ 39.13 [Amended] Regulatory Text 2. The FAA amends § 39.13 by adding the following new airworthiness directive:

2026-07-03 DG Aviation GmbH (Type Certificate Previously Held by DG Flugzeugbau GmbH):
Amendment 39-23298; Docket No. FAA-2026-2727; Project Identifier MCAI-2025-00685-G.

(a) Effective Date

This airworthiness directive (AD) is effective April 20, 2026.

(b) Affected ADs

None.

(c) Applicability

This AD applies to all DG Aviation GmbH (type certificate previously held by DG Flugzeugbau GmbH) Model DG-1000M gliders,
certificated in any category.

(d) Subject

Joint Aircraft System Component (JASC) Code 5346, Powerplant Attach Fittings.

(e) Unsafe Condition

This AD was prompted by reports of the engine mount cracking near the propeller head. The FAA is issuing this AD to detect
and correct indications of structural failure of the engine mount. The unsafe condition, if not addressed, could result in
loss of power transmission to the propeller and reduced or loss of control of the glider.

(f) Compliance

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

(g) Definitions

For the purpose of this AD, the definitions in paragraphs (g)(1) through (3) of this AD apply.

(1) An “affected part” is a steel frame engine mount having part number (P/N) 10M112.

(2) A “serviceable part” is an affected part which is new (never previously installed on any glider), or a part that has passed
the engine mount inspection prior to installation in accordance with Instructions 2 of DG Aviation GmbH Technical Note No.
TN 1000/51, Doc. No. TM1000-51 FE-29-01, Issue 01.d, dated February 26, 2025 (DG Aviation GmbH TN TM1000-51 FE-29-01, Issue
01.d).

(3) The “Old MM” task is the DG Aviation Maintenance Manual (MM) for DG-1000M, task 4.10.2 “Mounting and tensioning of the
drive belts”, issued before January 2025.

(h) Required Actions

(1) Before the next engine operation after the effective date of this AD, revise page 0.13 of the applicable MM in accordance
with paragraph 1 of the Instructions section of DG Aviation GmbH TN TM1000-51 FE-29-01, Issue 01.d.

(2) Before the next engine operation after the effective date of this AD, inspect the affected part for cracks and, if necessary,
before further flight, do one of the following:

(i) Repair or replace the affected part, as applicable, in accordance with paragraph 2 of the Instructions section of DG Aviation
GmbH TN TM1000-51 FE-29-01, Issue 01.d; or

(ii) Contact either the Manager, International Validation Branch, FAA; European Union Aviation Safety Agency (EASA); or DG
Aviation GmbH's EASA Design Organization Approval (DOA); for approved repair instructions and, within the compliance time
specified therein, accomplish those instructions accordingly, including post-repair follow-on action(s), as applicable. If
approved by the DOA, the approval must include the DOA-authorized signature; or

(iii) Replace an affected part with a serviceable part.

(3) Before the next engine operation after the effective date of this AD, accomplish the powerplant belt tension inspection
and, if necessary, adjust the belt tension in accordance with paragraph 3 of the Instructions section of DG Aviation GmbH
TN TM1000-51 FE-29-01, Issue 01.d.

(4) Within 15 hours time-in-service (TIS) of engine operation or 11 months, whichever occurs first after the effective date
of this AD, install a carbon fiber-reinforced plastic (CFRP) bracket having P/N 10M227 between the brackets of the two upper
drive belt guide rollers in accordance with paragraph 4 of the Instructions section of DG Aviation GmbH TN TM1000-51 FE-29-01,
Issue 01.d.

(5) Within 15 hours TIS of engine operation or 11 months, whichever occurs first after the effective date of this AD, perform
dynamic balancing of the propeller assembly in accordance with paragraph 5 of the Instructions section of DG Aviation GmbH
TN TM1000-51 FE-29-01, Issue 01.d.

(6) From the effective date of this AD, do not accomplish any maintenance action on a sailplane in accordance with the instructions
of the old MM task, as defined in paragraph (g)(3) of this AD.

(i) Installation Prohibition

As of the effective date of this AD, do not install a steel frame engine mount that is an affected part as defined in paragraph
(g)(1) of this AD on any glider, unless it is a serviceable part as defined in paragraph (g)(2) of this AD.

(j) Special Flight Permits

A one-time special flight permit may be issued in accordance with 14 CFR 21.197 and 21.199 only in order to fly to a maintenance
base to perform the required action in this AD and must specify that the engine not be operated.

(k) 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 (l) of this AD and email to AMOC@faa.gov. 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.

(l) Additional Information

For more information about this AD, contact Evan Weaver, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury,
NY 11590; phone: (316) 944-8910; email: evan.p.weaver@faa.gov.

(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) DG Aviation GmbH Technical Note No. TN 1000/51, Doc. No. TM1000-51 FE-29-01, Issue 01.d, dated February 26, 2025.

(ii) [Reserved]

(3) For DG Aviation GmbH material identified in this AD, contact DG Aviation GmbH, Rita Rodrigues, Otto Lilienthal Weg 2/Am
Flugplatz, Bruchsal, Germany; phone: +49 (0) 7251 36660-32; email: rodrigues@dg-aviation.de; website: dg-aviation.de/en/dg-flugzeugbau/contact.

(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 fr.inspection@nara.gov.

Issued on March 24, 2026. Steven W. Thompson, Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service. [FR Doc. 2026-06534 Filed 4-2-26; 8:45 am] BILLING CODE 4910-13-P

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