What happened
On May 20, 2010, an Avianca Brasil Fokker F28MK0100, registration PR-OAD, departed Brasília International Airport (SBBR) bound for Confins (SBCF). During the takeoff roll, near rotation speed, the crew experienced heavy vibrations throughout the airframe. Simultaneously, the landing gear lever became stuck in the down position, and a cockpit warning light appeared.
Following coordination with the operator, the crew decided to return to Brasília. Upon landing, the vibration intensified significantly at approximately 100 knots, resulting in the loss of the braking system and partial loss of ground control. The aircraft eventually came to a halt near the end of the runway. All 95 passengers and 5 crew members were unharmed, though the aircraft sustained severe damage to the main landing gear, including the wheels, tires, brakes, and shock absorbers.
The investigation
CENIPA investigators, with assistance from the Dutch Safety Board, examined the landing gear components at Fokker Services laboratories in the Netherlands. The investigation focused on recent maintenance performed on the aircraft's Torque Link Dampers.
Technical analysis revealed that the main landing gear structures were missing required spacers during the assembly of the Torque Link Dampers. This omission created a 4.5mm clearance, which allowed the dampers to vibrate excessively during taxi, takeoff, and landing. This progressive vibration eventually caused the shearing of the torque link pivot pins. Once the pins sheared, the wheels were free to rotate 360 degrees, leading to the destruction of hydraulic hoses, tires, and the braking system.
Findings
- Inadequate maintenance: During a routine replacement of the Torque Link Dampers, technicians failed to reinstall the specified spacers.
- Maintenance oversight: It is believed that a large amount of grease in the area caused the spacers to be hidden from view during the procedure. Because this was the first time the operator's mechanics had performed this specific task, they failed to notice the omission.
- Inadequate supervision: Although the maintenance was subject to inspection, the supervisory process failed to identify the missing components.
- Loss of control: The shearing of the pivot pins caused the wheels to rotate freely, leading to the loss of braking and ground steerability.