What distinguishes 'fly by wire' systems in aircraft?

'Fly by wire' systems in aircraft are characterized by control linkages that are purely electronic, meaning that pilot inputs are translated into electronic signals rather than being transmitted through mechanical connections. This allows for a much more sophisticated and responsive flight control system. The electronic signals are processed by flight control computers, which can make real-time adjustments to enhance flight safety and optimize performance, providing pilots with an overall enhanced flying experience.

In a traditional mechanical control system, movements in the cockpit translate directly through cables and pulleys to the control surfaces. This is not the case with fly by wire systems; instead, the pilot's inputs are first interpreted electronically and then executed by actuators. Moreover, the ability to incorporate advanced flight control laws allows for automated adjustments that can enhance the aircraft's stability and maneuverability.

Other options involve different control systems. Mechanical linkages would not be electronic and lack the advanced functionalities of a fly by wire system. Hydraulic systems can be part of a fly by wire system, but they are not a defining characteristic by themselves. Direct control implies an unmediated connection similar to mechanical systems, rather than through electronic means.