What happened
During the landing rollout phase, the aircraft experienced a mechanical failure involving the thrust reverser relay circuit board. This malfunction prevented the thrust reversers from deploying as intended when the pilot attempted to activate them. As a result of this failure, the cockpit indicators for both the 'reversers in transition' and 'reversers deployed' states failed to illuminate.
Despite the aircraft flight manual providing specific warnings against advancing the reverser throttle levers into the power range without confirmed light illumination, the pilot proceeded to move the levers into the power range. This action occurred even after the activation of the throttle mismatch warning horn. The continued application of reverse power led to an increase in forward thrust while the aircraft was attempting to decelerate.
Simultaneously, the second-in-command engaged the parking brake lever to the full override position. This action effectively locked the main wheel brakes and bypassed the functionality of the antiskid system during the critical deceleration period.