N699CZ

On April 30, 2022, about 1000 central daylight time, a Beech B-99 airplane, N699CZ, was substantially damaged when it was involved in an accident at General Mitchell International Airport (MKE), Milwaukee, Wisconsin. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 135 cargo flight.

The flight originated from Baraboo/Wisconsin Dells Regional Airport (DLL), Baraboo, Wisconsin, with MKE as the intended destination. As the airplane approached MKE, the pilot was cleared by air traffic control (ATC) for the visual approach for runway 19R. He noted that the landing was “smooth given the weather conditions,” and he used normal braking to exit the runway. Upon entering the ramp area, the green right landing gear position light extinguished, and the red gear handle light illuminated. The pilot glanced over to the circuit breaker panel and noticed that the “Landing Gear Control” circuit breaker had tripped. After parking the airplane for refueling, he notified his company maintenance control group about the issue and was advised to not reposition the airplane after refueling. The pilot waited about 20 minutes for weather to clear before exiting the airplane. As he prepared to exit the airplane, the right main landing gear collapsed and the airplane’s right wing impacted the ground, resulting in substantial damage to the right wing.

After the accident, it was discovered that the right landing gear drag leg support fitting, part number 50-120201-1, had broken. Further examination by the operator determined that the same part on the left landing gear was also fractured.

Metallurgical examination of the separated fracture surface on the right landing gear drag leg support fitting revealed an area of fatigue in a machined radius adjacent to the center lug of the drag leg support. The remainder of the fracture exhibited features consistent with overload failure. An additional crack was found in the machined radius on the opposite side of the center lug. This portion of the part had not completely separated. Exposure of the crack revealed the existence of a fatigue crack in about the same area as the first crack, with overload signatures outside of the fatigue area.

Maintenance manual excerpts for the airplane indicated that the subject part was to be cleaned and visually inspected at least every 7,500 cycles or every 5 years, whichever occurred first. If visual examination revealed a crack, it was to be verified by dye penetrant inspection. Any cracks found required replacement of the part. Maintenance records indicated that the part had accumulated 762 cycles since the last inspection 23 months prior.

The operator reported that the accident airplane was maintained using an Approved Aircraft Inspection Program (AAIP) and had accumulated 35,012.9 total flight hours and 43,054 total cycles at the time of the accident. The most recent inspection of the drag leg support fitting was performed on May 11, 2020.

The operator examined all the drag leg support fittings on their fleet of nine Beech B-99 airplanes, not including the accident airplane. Of the 18 drag leg support fittings examined, 14 were found to be cracked. Of the 14 cracked fittings, 11 required dye penetrant inspection to be detected; the cracks could not be detected solely by visual inspection.

The operator had a previous accident (NTSB report number ERA21LA021), on October 14, 2020, involving another Beech B-99 airplane. In that accident, the right main landing gear collapsed as the airplane was taxied from the runway after landing. The drag leg support fitting was also found to have fatigue cracking in the same area of the fitting.