With a green hydraulic system failure only, which brake system is not available?

In the case of a green hydraulic system failure, the autobrakes are not available. The autobrake system relies on the green hydraulic system for operation, as it uses hydraulic pressure to automatically apply the brakes during various phases of flight, particularly during landing. With the green hydraulic system lost, the electronic control signal is still present, but without the necessary hydraulic pressure, the autobrake functionality becomes inoperative.

On the other hand, the parking brake, antiskid system, and accumulator brakes can still function despite the failure of the green hydraulic system. The parking brake can be applied manually and is generally operated using different hydraulic sources, while the antiskid system can still function using alternate hydraulic systems (if available). Additionally, the accumulator can provide enough hydraulic pressure for braking momentarily, allowing for some braking action despite the failure. Thus, understanding the reliance on specific hydraulic systems is crucial for recognizing which components remain operable during such failures.