Final answer:
The nosewheel steering on the Challenger 605 is actuated by a hydraulic system, which provides the necessary control and power for steering the nosewheel.
Step-by-step explanation:
The nosewheel steering in the Challenger 605 aircraft is actuated hydraulically. This means that the aircraft uses a system that employs fluid pressure to enable the steering of the nosewheel. Hydraulic systems are commonly used in aircraft for many control functions because they can deliver a high amount of power through small tubes and hoses, and the fluid in the system can be used to absorb some of the shocks and vibrations encountered during operations.