What happened
On January 8, 2014, an Aero Boero AB-115, registration PP-GSG, was conducting a local training flight departing from and returning to the Santarém Aerodrome (SBSN) in Pará, Brazil. The aircraft was operated by Aeroclube de Santarém and carried a pilot and one passenger.
Upon landing on runway 10, the pilot noticed an unusual noise originating from the left main landing gear. Immediately following the touchdown, the aircraft began to yaw to the right. The aircraft subsequently exited the runway and came to a stop on the grass area on the right side of the pavement. The airport's fire and rescue services responded to the scene to assist in repositioning the aircraft. While the occupants were uninjured, the aircraft sustained substantial damage.
The investigation
CENIPA investigators examined the landing gear assembly to determine the cause of the directional instability. The investigation focused on the left main landing gear, specifically the wheel hub, bearing, and brake assembly.
Technical analysis of the left main wheel bearing revealed characteristic marks of a fracture caused by lateral overload. This overload resulted in the crushing of the bearing rollers against the bearing race, leading to the failure of the bearing and subsequent damage to the wheel hub and brake assembly. This mechanical failure prevented the left brake from functioning effectively. The investigation also noted that the left landing gear leg sustained damage because the wheel momentarily rotated out of its normal axis.
Findings
- The primary cause of the excursion was a hard and misaligned landing to the right, which generated a lateral overload on the left landing gear.
- The resulting bearing failure caused the left brake to lose effectiveness, leading to the loss of directional control.
- The pilot had relatively limited experience, having recently completed flight instructor training in October 2013, with only 40 hours of flight time in this specific aircraft model.
- The pilot's application of control inputs contributed to the occurrence.