What happened
On August 20, 2014, an Aero Boero AB-115, registration PP-FLF, was performing a flight instruction mission at Rio Claro Aerodrome (SDRK) in São Paulo. The crew, which included a student pilot being prepared for instructor qualification, had completed a successful first landing and a subsequent go-around without noticing any irregularities.
During the second landing attempt, as the aircraft was decelerating on the runway, the crew heard a loud snap followed by the aircraft dropping on its left side and yawing sharply to the left. The aircraft veered off the side of the runway, resulting in substantial damage to the left landing gear and minor damage to the left wingtip. The two occupants of the aircraft were unharmed.
The investigation
CENIPA investigators examined the landing gear assembly to determine why the left gear collapsed. The investigation established that the landing gear fork (PN 1005-18) had completely detached from the fuselage. While the fork itself had not fractured, the self-locking nut (PN 1005-22) had come off entirely.
Upon inspection of the components, investigators found that the threads on the fork were heavily worn, which compromised the ability of the nut to remain securely fastened. Furthermore, the nylon insert within the self-locking nut, which provides the necessary resistance to prevent loosening, was significantly degraded. The investigation noted that the nut could be threaded onto the fork by hand without any tools, indicating that the locking mechanism was non-functional. This allowed for movement and friction between the nut and the threads, eventually leading to the detachment of the assembly during the landing roll.
Findings
- Maintenance of the aircraft
- Management supervision