AD 2024-16-06 Airworthiness Directives; Air Tractor, Inc. Airplanes

Models named: AT-802, AT-802A. Read the applicability below — it usually turns on serial or part numbers too.

This AD applies to Air Tractor, Inc. Model AT-802 and AT-802A airplanes, all serial numbers, certificated in any category, that have Wipaire, Inc. Supplemental Type Certificate (STC) No. SA01795CH installed.

Comply with this AD within the compliance times specified, unless already done.

(1) Within 7 days after the effective date of this AD or before the airplane accumulates 110 hours time-in-service (TIS) after installation of STC No. SA01795CH, whichever occurs later, and thereafter at intervals not to exceed 110 hours TIS until the airplane is modified as required by paragraph (g)(3) of this AD: Inspect the left and right horizontal stabilizer spars for cracks in accordance with Steps 1 through 9 of the Work Instructions—Inspection, Method 1 in Wipaire, Inc. Service Letter 253, Revision D, dated July 3, 2024 (Wipaire SL 253D). (2) If any crack is found in a horizontal stabilizer spar during any inspection required by paragraph (g)(1) of this AD, or if any crack, elongated hole, or corrosion is found in a horizontal stabilizer spar during any inspection required by paragraph (g)(4) of this AD, before further flight, replace the horizontal stabilizer spar. (3) Within 300 hours TIS or 12 months after the effective date of this AD, whichever occurs first, install bathtub fittings (Service Kit 1012347-01 or 1012347-02) in accordance with Steps 1 through 10 of the Work Instructions—Install Bathtub Fittings in Wipaire SL 253D except where Step 2 specifies that to be eligible for reinstallation, finlet mount weldments must include the welded gussets shown in figure 8 of Wipaire SL 253D, that constraint is not required by this AD. If any spars were previously modified by installing 7D1-4399 Revision L or earlier, regardless of condition, those spars must be replaced at the same time the bathtub fittings kit is installed. (4) Within 110 hours TIS after installing the bathtub fittings, and thereafter at intervals not to exceed 110 hours TIS, inspect the horizontal stabilizer spars for cracks, elongated holes, and corrosion in accordance with Steps 1, 2, 4 through 6, 9, and 10 of the Work Instructions—Inspection, Method 2 in Wipaire SL 253D. (5) Within 5 days after each inspection required by paragraphs (g)(1) and (4) of this AD or within 5 days after the effective date of this AD, whichever occur later, report the following to the FAA at the address in paragraph (j)(1) of this AD. Report this information regardless of whether cracks are found. (i) Model, engine configuration (with horsepower limits), and propeller type; (ii) Serial number and N number; (iii) Total hours TIS on airframe; (iv) Total hours TIS operated with floats, if known; (v) STC configuration and total hours with STC installed; (vi) Crack location (right or left, upper/lower caps inboard/outboard hole); (vii) Crack size; (viii) Photos of cracks found, if available; and (ix) Any additional operator/mechanic comments.

This AD was prompted by additional reports of cracks found in the horizontal stabilizer spars and the need to incorporate a new finlet attach design on the horizontal stabilizer spars to reduce the cracking. The FAA is issuing this AD to prevent structural failure of the horizontal stabilizer spars. The unsafe condition, if not addressed, could result in structural failure of the horizontal tail with consequent loss of control of the airplane.

This AD replaces AD 2023-15-07, Amendment 39-22519 (88 FR 53761, August 9, 2023) (AD 2023-15-07).