You buy a well-maintained Diamond DA40, keep up with the annuals, and trust that a modern composite aircraft is holding together the way it should. What you don't know is that the factory-installed fuel tank connection hoses are slowly breaking down, shedding rubber debris into your fuel system with every flight. That's the scenario behind AD 2026-06-03.

What's Happening: The fuel tank connection hoses on affected DA40, DA40 F, and DA40 NG airplanes use rubber inner liners that degrade over time. As the material breaks down, it enters the fuel system. Enough contamination means restricted fuel flow, fuel starvation, and reduced control. This AD supersedes 2020-14-06 after Diamond discovered additional production-installed hoses on DA40 NG airplanes that weren't captured the first time around.

What the AD Requires: Within 100 hours TIS or 2 months of the April 30, 2026, effective date: replace each affected hose, inspect the fuel tank chambers, and remove any rubber debris found. Use the Diamond service material applicable to your model. No affected hose may be installed on any airplane.

Field Notes:

The tank inspection isn't optional. Hose replacement alone doesn't close this AD; you must also document removal of any debris.

Watch the calendar. On a lightly flown DA40, 2 months arrives before 100 hours does.

Check the new serial number list. DA40 NG owners who complied with the 2020 AD may be back in scope. The expanded list is in MSB 40NG-064 Rev. 3.

DA40 D conversions aren't off the hook. If your airplane started life as a DA40 D and was converted to NG configuration, this AD applies to you. Don't assume a conversion puts you outside the applicability.

Rubber degradation inside a fuel system leaves no visible clues until the engine starts to stumble. TBX keeps compliance like this from falling through the cracks.

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