What happened
Upon touchdown, the pilot applied the brakes in a normal manner. Shortly thereafter, he noticed a significant softening of the left brake pedal. As the aircraft slowed, it began to turn to the right, eventually leaving the runway surface. The aircraft then intersected a taxiway at an approximate 30-degree angle.
The taxiway featured a six-inch rise at its edge. When the aircraft impacted this elevation, the left main gear collapsed upon impact. The incident resulted in substantial damage to the landing gear assembly and surrounding airframe components due to the force of the collision with the raised curb.
The investigation
A thorough examination of the braking system was conducted to determine the root cause of the loss of braking effectiveness on the left side. Investigators focused on the hydraulic lines, brake assemblies, and associated mechanical linkages. The inspection revealed that brake fluid had leaked out during the flight prior to this incident.
The source of the leak was identified as a cocked brake puck within the brake assembly. This misalignment prevented the system from maintaining proper hydraulic pressure, leading to the gradual loss of braking capability on the left side. The investigation confirmed that the mechanical failure occurred before touchdown, setting the stage for the subsequent runway excursion.
Findings
Several factors contributed to this incident. The primary issue was the loss of hydraulic pressure in the left brake system due to fluid leakage. This leak was directly caused by a cocked brake puck, which compromised the integrity of the braking mechanism. The pilot's inability to maintain directional control on the runway was a direct result of the asymmetric braking force.
The intersection with the taxiway at an acute angle exacerbated the damage. The six-inch rise at the edge of the taxiway acted as a rigid obstacle. When the left main gear struck this elevation, the structural integrity of the landing gear was exceeded, leading to collapse. The combination of brake failure and the physical obstruction resulted in the final outcome.
Safety message
Regular inspection of brake components is critical to identifying potential issues such as cocked brake pucks before they lead to fluid leaks. Pilots should be aware that a softening brake pedal can indicate hydraulic system failures and may require immediate attention upon touchdown.