# 2026-15466: FAA Grounds Glider Fuel Leaks on Tiny Copper Sealing Rings

2026-15466, Airworthiness Directives; Stemme GmbH Gliders, is a Federal Register rule from Transportation Department, Federal Aviation Administration published 2026-07-30, effective 2026-09-03; PRIA reads it as touching household money (as of 2026-10-28).

- Canonical: https://policyrisk.com/federal-register/2026-15466
- As of: 2026-10-28
- Plain-text twin of the page above; the HTML and this file carry the same facts.

## Facts
- Document number: 2026-15466
- Title: Airworthiness Directives; Stemme GmbH Gliders
- Type: Rule
- Agencies: Transportation Department; Federal Aviation Administration
- Citation: 91 FR 47940
- Published: 2026-07-30
- Effective: 2026-09-03
- Comments close: not stated
- Significant: no
- Touches household money: yes
- Regulation identifier numbers: 2120-AA64
- Last updated: 2026-10-28

## In one line

FAA Grounds Glider Fuel Leaks on Tiny Copper Sealing Rings

## Summary

If you own a Stemme S 12 glider, listen up! The FAA found fuel leaks caused by faulty copper sealing rings and now requires regular fuel system checks and replacing those rings. Starting September 3, 2026, you can’t install the bad parts anymore, so get ready to keep your glider safe without breaking the bank.

## Abstract

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.

## Effects PRIA read

- Rule applies to all Stemme S 12 gliders: cost, medium. This AD applies to every Stemme Model S 12 glider certificated in any category. Note: the rule states that all of the affected airplanes were produced and delivered with the affected copper sealing rings installed. The AD becomes effective September 3, 2026.
- Mandatory preflight fuel-leak checks: cost, low. If your Stemme S 12 has the affected copper sealing ring (Group 1), you must visually check the fuel system for leaks (staining, wetness, dripping) before further flight after September 3, 2026 and before each flight until the ring is replaced. The AD explicitly allows an owner/operator holding at…
- Required replacement of sealing rings: cost, medium. For gliders with affected parts, you must replace each affected copper sealing ring with sealing ring P/N 831984 in accordance with Stemme Service Bulletin P062-980082, Revision 01, by whichever occurs first: before further flight if any leakage is found, or within 100 hours time-in-service after S…
- Ban on reinstalling affected sealing rings: cost, low. As of September 3, 2026, you may not install the affected copper sealing ring part number D7603-12016-CU on any Stemme S 12 glider. The AD contains an explicit installation prohibition applying to both gliders that currently have the part and those that do not.
- FAA estimated U.S. fleet cost and scope: cost, medium. The FAA estimates this AD affects 31 Stemme S 12 gliders on the U.S. registry. Estimated costs: a visual check is 1 work-hour ($85) totaling $85 per glider (FAA total $2,635), and replacement is estimated at $320 per glider (2 work-hours = $170 plus $150 parts) for a FAA total of $9,920 across U.S.…

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## Sources
- [2026-15466 on federalregister.gov](https://www.federalregister.gov/documents/2026/07/30/2026-15466/airworthiness-directives-stemme-gmbh-gliders)
- [2026-15466 as published (PDF)](https://www.govinfo.gov/content/pkg/FR-2026-07-30/pdf/2026-15466.pdf)

## Related
- [Previous: 2026-15455, Airworthiness Directives; Airbus SAS Airplanes](https://policyrisk.com/federal-register/2026-15455)
- [Next: 2026-15467, Airworthiness Directives; Pilatus Aircraft Ltd. Airplanes](https://policyrisk.com/federal-register/2026-15467)
- [All Federal Register documents](https://policyrisk.com/federal-register)

Source: PRIA, https://policyrisk.com/federal-register/2026-15466 (as of 2026-10-28).