HISTORY OF FLIGHTOn July 27, 2023, at 1430 central daylight time, an Air Tractor AT-802A airplane, N8503W, was substantially damaged when it was involved in an accident at the Aberdeen Regional Airport, (ABR) Aberdeen, South Dakota. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. The pilot reported that while taxiing from the loading ramp to depart for his third agricultural application flight of the day, the airplane veered left. He attempted to correct by braking, but the airplane did not respond and continued turning to the left. With the pilot unable to arrest the turn, the airplane ground looped to the left. During the ground loop, the right main landing gear collapsed, and the right wing impacted the surface which resulted in substantial damage. METEOROLOGICAL INFORMATIONThe calculated tailwind component was about 6 kts and the calculated crosswind component was about 10 kts. WRECKAGE AND IMPACT INFORMATIONExamination of the accident site revealed that the airplane was taxiing southbound on taxiway C toward runway 35, departed the left side of the taxiway, and came to rest on a 240° heading. The right main landing gear was separated from and folded beneath the fuselage. Dark, arcing tire marks on the taxiway surface continued into the grass and ended at the left main landing gear. Tire marks aligned with the right main landing gear began on the taxiway surface, continued into the grass, and terminated at the right main landing gear.

Examination of the recovered wreckage revealed substantial damage to the right wing and the main landing gear mount structure. The right main landing gear attachment hardware was retained and forwarded to the NTSB Materials Laboratory in Washington, DC, for examination. The hardware was examined using a bench binocular microscope and a hardness tester, which revealed fracture features consistent with overstress separation, with no evidence of fatigue cracking.

Postaccident examination of the brake system revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation. The brake system was partially disassembled during the recovery of the wreckage from the accident site. Control continuity for the brake system was established from the cockpit controls to the left and right main landing gear. The hardware for the brake system was installed and intact. Both brakes were actuated inside the cockpit with no issues or interference noted.

There were no observed fluid leaks within the brake system. A small amount of brake fluid was extracted from the right side of the brake system. The brake fluid had a red appearance, with several small pieces of dark-colored debris. There was not enough fluid recovered to be tested for impurities.

The brake cylinder in the cockpit was found connected and showed no fluid leaks. Both brake calipers were found removed and appeared to be in normal condition, with no damage or fluid leaks. Both brake discs showed normal wear with no damage or obvious warping. Both tires showed normal wear with no major damage.