Old aircraft connected the stick to the control surfaces with cables and rods. Modern ones use wires and computers. Fly-by-wire replaces mechanical linkage with electronic signals, and the flight control computer decides how much to move each surface.

The change saves weight and allows designers to build aircraft that would be unstable with direct controls. Fighter jets and airliners both rely on it. The computer can also enforce limits, preventing the pilot from overstressing the airframe or stalling.

Common architectures

• Analog fly-by-wire in early systems
• Digital fly-by-wire with redundant computers
• Power-by-wire for electrically actuated surfaces
• Hybrid systems retaining some mechanical backup

Redundancy is critical. Multiple computers vote on each command, and a failed channel gets isolated automatically. When the system misbehaves, pilots have caused accidents by fighting automation rather than understanding it.