Incident Overview
During the early stage of the takeoff roll, the aircraft lost directional control. It departed the runway 400 feet down the runway and traveled 85 feet off the side of the runway. One runway light was destroyed in the incident.
Brake System Modification
The aircraft had been delivered from the factory equipped with an anti-skid brake system. Prior to the aircraft's first passenger flight, the anti-skid system was replaced with a standard braking system.
Hydraulic Line Reversal
During the replacement process, hydraulic lines attached to the parking brake shuttle valve under the instrument panel area were inadvertently reversed. This error caused braking action to occur on the opposite landing gear of the brake pedal being depressed. For example, pressing the left brake pedal would apply brakes to the right landing gear, and vice versa.
Crew Awareness
The flight crew was unaware of the brake system malfunction because they had been using asymmetrical thrust for directional control in previous operations. During the takeoff roll in this incident, they likely attempted to use brakes for directional control, which resulted in the opposite effect, leading to loss of directional control and the subsequent runway excursion.