Airworthiness Directives; Stemme GmbH Gliders

[Federal Register Volume 91, Number 145 (Thursday, July 30, 2026)]
[Rules and Regulations]
[Pages 47940-47942]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-15466]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2026-4637; Project Identifier MCAI-2025-01226-G; 
Amendment 39-23420; AD 2026-15-08]
RIN 2120-AA64


Airworthiness Directives; Stemme GmbH Gliders

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all 
Stemme GmbH (Stemme) Model Stemme S 12 gliders. This AD was prompted by 
reports of fuel leaking around certain copper sealing rings within the 
fuel system. This AD requires repetitive visual checks of the fuel 
system for fuel leakage, and replacement of the affected copper sealing 
ring. This AD also prohibits the installation of affected parts. The 
FAA is issuing this AD to address the unsafe condition on these 
products.

DATES: This AD is effective September 3, 2026.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of September 3, 
2026.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2026-4637; 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-91, West Building Fifth Floor, Room W58-213, 1200 
New Jersey Avenue SE, Washington, DC 20590.

Material Incorporated by Reference

    <bullet> For Stemme material identified in this AD, contact Stemme, 
Flugplatzstrasse F2 Nr. 6-7, Strausberg, Germany 15344; phone: +49 (0) 
3341 3612; email: stemme.com">airworthiness@stemme.com; website: stemme.com.
    <bullet> You may view this material at the FAA, Airworthiness 
Products Section, Operational Safety Branch, 1100 Main, Kansas City, MO 
64105. 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-2026-4637.

FOR FURTHER INFORMATION CONTACT: George Weir, Aviation Safety Engineer, 
FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (817) 
222-4045; 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 all Stemme Model Stemme 
S 12 gliders. The NPRM was published in the Federal Register on May 15, 
2026 (91 FR 27876). The NPRM was prompted by European Union Aviation 
Safety Agency (EASA) AD 2025-0155, dated July 21, 2025, issued by EASA, 
which is the Technical Agent for the Member States of the European 
Union (EASA AD 2025-0155) (referred to as the MCAI). The MCAI states 
that occurrences of fuel leaks at multiple locations within the fuel 
system have

[[Page 47941]]

been reported. To address the unsafe condition, Stemme published 
service material to provide replacement instructions for affected 
copper sealing rings, and a parts installation restriction. This 
condition, if not addressed, could result in an in-flight fire.
    In the NPRM, the FAA proposed to require repetitive visual checks 
of the fuel system for fuel leakage (staining, wetness, dripping, 
etc.), and replacement of the affected copper sealing rings if leakage 
is detected. In addition, the FAA proposed to prohibit the installation 
of affected parts. The owner/operator (pilot) holding at least a 
private pilot certificate may perform the visual check and must enter 
compliance with the applicable paragraph of this AD into the glider 
maintenance records in accordance with 14 CFR 43.9(a) and 
91.417(a)(2)(v). The pilot may perform this action because it only 
involves visually checking affected locations for fuel leakage. This 
action could be performed equally well by a pilot or a mechanic. This 
is an exception to the FAA's standard maintenance regulations. 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-2026-4637.

Discussion of Final Airworthiness Directive

Comments

    The FAA received no comments on the NPRM or on the determination of 
the costs.

Conclusion

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

Material Incorporated by Reference Under 1 CFR Part 51

    The FAA reviewed Stemme Service Bulletin (SB) P062-980082, Revision 
01, dated July 15, 2025. This material specifies procedures for 
replacement of affected copper sealing rings within the fuel pump set 
assembly and drainer complete assembly.
    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 31 gliders of U.S. registry. 
The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
Visual check of fuel system...........  1 work-hour x $85 per                 $0             $85          $2,635
                                         hour = $85.
Replacement of copper sealing rings...  2 work-hours x $85 per               150             320           9,920
                                         hour = $170.
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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:

2026-15-08 Stemme GmbH: Amendment 39-23420; Docket No. FAA-2026-
4637; Project Identifier MCAI-2025-01226-G.

(a) Effective Date

    This airworthiness directive (AD) is effective September 3, 
2026.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to all Stemme GmbH Model Stemme S 12 gliders, 
certificated in any category.

    Note 1 to paragraph (c): All of the affected airplanes were 
produced and delivered with the affected copper sealing rings 
installed.

(d) Subject

    Joint Aircraft System Component (JASC) Code 2800, Aircraft Fuel 
System.

(e) Unsafe Condition

    This AD was prompted by reports of fuel leaking around certain 
copper sealing rings within the fuel system. The FAA is issuing this 
AD to prevent fuel leakage in the fuel

[[Page 47942]]

system. The unsafe condition, if not addressed, could result in an 
in-flight fire.

(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 (4) of this AD apply.
    (1) An ``affected location'' is any of the following:
    (i) The copper sealing ring within the fuel pump set assembly 
having part number (P/N) 128201, between the screw-in adapter having 
P/N 831099 and the fuel distributor having P/N 128229, and between 
the screw-in adapter having P/N 831099 and the fuel distributor 
having P/N 128228. The fuel pump set assembly P/N 128201 is located 
at the front left area of the middle fuselage and may be accessed 
from below when the main landing gear is extended. (Location defined 
in Stemme Service Bulletin (SB) P062-980082, Revision 01, dated July 
15, 2025, Page 1 of 3, Action 2 and Figure 1).
    (ii) The copper sealing ring within the drainer complete having 
P/N 128207, between the screw-in adapter having P/N 831099 and the 
drainer attachment having P/N 128271. The drainer complete P/N 
128207 is located at the main landing gear bay and may be accessed 
from below when the main landing gear is extended. (Location defined 
in Stemme SB P062-980082, Revision 01, dated July 15, 2025, Page 2 
of 3, Action 3 and Page 3 of 3 Figure 2).
    (2) An ``affected part'' is a copper sealing ring having P/N 
D7603-12016-CU.
    (3) ``Group 1 gliders'' are gliders that have an affected part 
installed.
    (4) ``Group 2 gliders'' are gliders that do not have an affected 
part installed.

(h) Required Actions

    (1) For Group 1 gliders, before further flight after the 
effective date of this AD and thereafter before each flight until 
the replacement required by paragraph (h)(2) is accomplished, 
perform a visual check using a light source of the affected 
locations for indications of fuel leakage (staining, wetness, 
dripping, etc.). The owner/operator (pilot) holding at least a 
private pilot certificate may perform the visual check and must 
enter compliance with the applicable paragraph of this AD into the 
glider maintenance records in accordance with 14 CFR 43.9(a) and 
91.417(a)(2)(v). The record must be maintained as required by 14 CFR 
91.417.
    (2) For Group 1 gliders, at whichever compliance time in 
paragraph (h)(2)(i) or (ii) that occurs first, replace the affected 
part at each affected location with a sealing ring having P/N 831984 
in accordance with the instructions of Action 2 or Action 3 of 
Stemme SB P062-980082, Revision 01, dated July 15, 2025, as 
applicable.
    (i) Before further flight if any leakage is detected during any 
preflight check required by paragraph (h)(1) of this AD.
    (ii) Within 100 hours time-in-service after the effective date 
of this AD.

(i) Installation Prohibition

    For Group 1 and Group 2 gliders: As of the effective date of 
this AD, do not install an affected part as defined in paragraph 
(g)(2) of this AD on any glider.

(j) 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 (k) 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.

(k) Additional Information

    For more information about this AD, contact George Weir, 
Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, 
Westbury, NY 11590; phone: (817) 222-4045; email: 
[email protected].

(l) 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) Stemme Service Bulletin P062-980082, Revision 01, dated July 
15, 2025.
    (ii) [Reserved]
    (3) For Stemme material identified in this AD, contact Stemme 
GmbH, Flugplatzstrasse F2 Nr. 6-7, Strausberg, Germany 15344; phone: 
+49 (0) 3341 3612; email: stemme.com">airworthiness@stemme.com; website: 
stemme.com.
    (4) You may view this material at the FAA, Airworthiness 
Products Section, Operational Safety Branch, 1100 Main, Kansas City, 
MO 64105. 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 July 24, 2026.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2026-15466 Filed 7-29-26; 8:45 am]
BILLING CODE 4910-13-P

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