What happened
The aircraft departed the runway shortly after beginning its takeoff roll. Directional control was lost in the early stage of the ground run, causing the airplane to veer off the paved surface. The aircraft traveled approximately 85 feet laterally from the edge of the runway before coming to a stop. During this excursion, one runway light was destroyed by the impact.
The investigation
Examination of the aircraft revealed that it had previously been equipped with an anti-skid brake system when it left the factory. Prior to its first passenger flight, this system had been replaced with a standard braking configuration. During that maintenance process, hydraulic lines connected to the parking brake shuttle valve located under the instrument panel were inadvertently reversed.
This installation error allowed braking action to occur on the opposite main landing gear from the side where the pilot depressed the brake pedal. Because the flight crew had relied on asymmetrical engine thrust for directional control during previous operations, they remained unaware of this latent defect until it manifested during this specific takeoff attempt.
Findings
The primary factor was the inadvertent reversal of hydraulic lines during the removal of the anti-skid system. This caused unintended braking on one side of the aircraft when the pilot applied brakes for steering correction. The crew's reliance on differential thrust masked the issue until it became critical during high-speed takeoff operations.
Safety message
Maintenance procedures involving the modification or removal of critical flight control systems must include rigorous functional testing to verify correct hydraulic routing and operation before returning the aircraft to service.