AD 2021-05-14 Prompted By Reports Of Cracks In The Flap Torque Tube Actuator Attachment Brackets

The FAA is adopting a new airworthiness directive (AD) for all Air Tractor, Inc., (Air Tractor) Models AT-250, AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-401A, AT401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, AT-502A, AT-502B, AT-503, AT-503A, AT-504, AT-602, AT-802, and AT-802A airplanes.

This AD was prompted by reports of cracks in the flap torque tube actuator attachment brackets that may cause the flap actuator to detach from the flap torque tube. This AD requires repetitive visual and dye penetrant inspections of the flap actuator attachment bracket welds for cracks and replacement if cracks are identified. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective April 29, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Air Tractor Models AT-250, AT-300, AT-301, AT-302, AT-400, AT400A, AT-401, AT-401A, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, AT-502A, AT-502B, AT-503, AT-503A, AT-504, AT-602, AT-802, and AT-802A airplanes. The NPRM published in the Federal Register on July 28, 2020 (85 FR 45347). The NPRM was prompted by
multiple reports of cracks in the brackets attaching the flap actuator motor to the flap torque tube on several models of Air Tractor airplanes.

One of the reports was on a Model AT-802A airplane where the brackets separated from the torque tube at the welds. The flaps suddenly retracted while maneuvering, and the pilot temporarily lost control of the airplane. The pilot was able to regain control of the airplane before it impacted the ground. Since then, there have been 13 reported airplanes with cracks in the flap torque tube attachment brackets.

The design of the flap actuator motor brackets on the Model AT-802A airplane is the same as on Models AT-250, AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-401A, AT-401B, AT402, AT-402A, AT-402B, AT-501, AT-502, AT-502A, AT-503, AT-503A, AT-504, AT-602, and AT-802 airplanes.

In the NPRM, the FAA proposed to require repetitive dye penetrant and visual inspections with replacement of the flap torque tube if cracks are found. The FAA is issuing this AD to address the unsafe condition on these products.

FMI: www.regulations.gov