Beech 99 N499CZ accident near Waterville, Maine

Probable cause

A failure of the right main landing gear drag leg support fitting and angle bracket as a result of multiple areas of fatigue cracking.

NTSB analysis

While taxiing to the ramp, the airplane’s right main landing gear collapsed, resulting in substantial damage to the right wing. Examination of the right main landing gear drag leg support fitting and angle bracket revealed several areas of fatigue cracking with multiple origins. The attach angle bracket fracture exhibited features consistent with fatigue. The reason for the crack initiation could not be determined.

A review of the maintenance procedures performed on the right main landing gear 8 days prior to the accident found that they instructed the mechanic to add grease to the drag leg fitting. The procedures did not specify to examine the landing gear for fatigue cracking or anomalies; therefore, it is unlikely that the mechanic would have looked in the area of the cracked main landing gear drag leg support fitting and angle bracket. Furthermore, there was no nondestructive testing procedures for examining the main landing gear drag brace, so it’s unlikely an inspection would have detected the multiple areas of fatigue cracking.

Text from the NTSB. Open the NTSB docket for ERA21LA021 for the full record.