Picture this: an AT-802 with floats, during peak fire season, working non-stop. It's scooping water from a lake, climbing hard, dropping the water, and doing that over and over for 100 hours each month. Every water landing sends a jolt up through the float struts and into the tail. Three ADs in three years say the airframe has been trying to tell someone exactly where that jolt keeps landing.

‍Field NotesThe Wipaire STC (SA01795CH) has been in continuous use since 2001, and it certifies these AT-802s for the fire bomber configuration, including a dedicated "Scooping Operations" mode, rated to 16,000 lbs, versus an 11,500 lb limit for a standard water takeoff or landing. Scooping means skimming the surface at speed to refill the tank without ever coming to a stop, a repeated, high-load water contact a landplane never sees.

The cracking first showed up in 2023 on the forward spar, near the finlet mounting locations. The 2024 fix, a reinforcing "bathtub fitting" doubler, stopped it there, but installing that fitting means removing and reinstalling the finlets themselves, and Wipaire's own service documentation notes that reinstallation can shift finlet position just enough to pre-load the finlet strut. In plain terms: the fix for one crack quietly set up the next one. AD 2024-16-06 also expanded inspections to the rear spar and tightened the interval to 110 hours TIS, as if anticipating the fatigue hadn't finished moving.

It found the next spot in 2026: where the finlet strut ties into that rear spar, what the AD itself calls the "vertical fin structural support brace" mount. Same finlet hardware family, new point of failure. AD 2026-16-12, effective August 31, 2026, adds an inspection there, due within 50 hours TIS or 7 days after the effective date, whichever occurs later, and every 50 hours TIS thereafter, stacked on top of, not replacing, everything the 2024 AD already required. The FAA calls this an interim action; a permanent spar life limit, potentially as low as 2,000 hours TIS, is still under evaluation, notably less than a third of the 7,800-hour limit Wipaire's own maintenance manual already uses. It was issued as an immediately effective final rule under the FAA's good-cause authority, with comments still open through September 28, 2026. An estimated 35 U.S.-registered aircraft carry this STC.

For shops doing the work: the new brace-mount inspection follows Wipaire Service Letter 277, Revision C (July 27, 2026), about 6 labor hours. The retained spar inspections now reference updated Service Letter 253, Revision H (also July 27, 2026), which folds in checks for elongated holes and corrosion alongside cracking, roughly 3 hours per cycle once bathtub fittings are installed. Already inspected under Wipaire SL 277, Revision A or B, before August 31, 2026? That satisfies the initial brace-mount check; no need to repeat it. Both service letters also require reporting every inspection directly to Wipaire, separate from the FAA reporting below, so a shop doing this work is feeding two different feedback loops at once.

‍Why It MattersThis isn't three unrelated ADs. It's one fatigue crack, chased across three years, that keeps resurfacing a few inches from wherever it was last reinforced, and this time, the manufacturer's own documentation says why: fixing the last crack physically disturbed the hardware that's now cracking.The FAA only knows where to look next because operators keep reporting under paragraph (j), on top of the separate reports Wipaire is collecting through its own service letters. For high-utilization ag and firefighting aircraft, an outdated compliance record isn't just an administrative gap, it's how the next crack goes unfound. On a tail structure, that means loss of control.

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