The FAA is superseding Airworthiness Directive (AD) 2023-15-07, which applied to all Air Tractor, Inc. (Air Tractor) Model AT-802 and AT-802A airplanes with Wipaire, Inc. Supplemental Type Certificate (STC) No. SA01795CH installed. AD 2023-15-07 required repetitive 200-hour time-in-service (TIS) inspections of the left and right forward horizontal stabilizer spars for cracks, replacing any forward horizontal stabilizer spar found cracked, and reporting inspection results to the FAA.
As a result of the reports of the inspections required by AD 2023-15-07, additional cracks have been found in the forward horizontal stabilizer spar, including cracks found before the airplane accumulated 200 hours TIS after installation of the STC. Accordingly, the FAA determined that reducing the inspection interval is necessary. In addition, based on a new fatigue analysis, the FAA determined that there is the potential for cracks in the rear horizontal stabilizer spar.
Wipaire, Inc. has developed a change to its STC, which incorporates an improved design that includes modification kits to install bathtub fittings on the horizontal stabilizer spars to mitigate this condition by improving the structural load path. This includes more accessible repetitive inspection intervals of 110 hours TIS.
This superseding AD requires:
- Repetitively inspecting the left and right, forward and rear, horizontal stabilizer spars for cracks at 110-hour TIS intervals, and replacing any horizontal stabilizer spar found cracked or damaged.
- Within 300 hours TIS or within 12 months after the AD effective date, installing bathtub fittings per Wipaire Service Letter 253, Revision D, dated July 3, 2024.
- After installing the bathtub fittings, repetitive 110-hour TIS interval inspections of the horizontal stabilizer spars for cracks, elongated holes and corrosion.
- Within 5 days after each inspection outlined in (1) and (3) above, reporting information to FAA, regardless of whether cracks are found.
AD 2024-16-06 is effective September 4, 2024.
