What happened
The incident occurred while the aircraft was executing a landing following a crop spraying mission. Upon touchdown, the pilot attempted to maintain directional control using the rudder and brakes. However, the right brake system failed to function properly, rendering it ineffective for stopping or steering the aircraft. As the plane continued down the runway, the rudder lost its effectiveness in maintaining the desired heading. Unable to stop within the available pavement, the aircraft departed the runway surface and collided with a berm located along the edge of the airfield. The impact caused the nose gear to collapse, resulting in the aircraft nosing over.
The investigation
A review of the aircraft's braking system revealed the specific mechanical failure responsible for the loss of braking capability. Inspection of the hydraulic components identified a worn O-ring with part number AN6227-11. This degraded seal allowed hydraulic fluid to bypass the brake mechanism rather than applying pressure to the brake pads. Consequently, the fluid returned directly to the reservoir without generating the necessary friction to slow the aircraft on the right side.
Findings
The primary factor contributing to this accident was the fuel system component failure, specifically the worn O-ring that compromised hydraulic pressure. This mechanical defect led to a complete loss of braking function on the right side, which prevented the pilot from keeping the aircraft on the runway when directional control via rudder was no longer sufficient.
Safety message
Regular inspection and replacement of hydraulic seals and O-rings are critical for maintaining brake system integrity. Pilots should be aware that partial brake failure may manifest as reduced stopping power or uneven braking, requiring immediate assessment of landing distance requirements.