FAA Grounds Glider Fuel Leaks on Tiny Copper Sealing Rings
Published Date: 7/30/2026
Rule
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.
Analyzed Economic Effects
5 provisions identified: 0 benefits, 5 costs, 0 mixed.
Rule applies to all Stemme S 12 gliders
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.
Required replacement of sealing rings
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 September 3, 2026.
FAA estimated U.S. fleet cost and scope
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. operators.
Mandatory preflight fuel-leak checks
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 least a private pilot certificate to perform and record this visual check.
Ban on reinstalling affected sealing rings
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.
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