A fly-by-wire system is an electronic interface of an aircraft that came to replace the traditional manual flight controls in the 1980s. It has now become an industry standard due to its handling qualities. Throughout the years, fly-by-wire has been praised for its commonality, improved flight safety, reduced pilot workload, a reduction of mechanical parts, and real-time monitoring of all aircraft systems.
Additionally, greater precision in flying, weight savings and lower maintenance are some of the positive points of the fly-by-wire system. The replacement of heavy mechanical control cables reduces significantly fuel consumption. Moreover, fly-by-wire translates into lower maintenance costs due to electrical controls being less complex and easier to maintain than mechanical one.
Commands are much more precise with direct input though electrical signals, thus improving the overall safety. To make sure that the aircraft is kept within the flight protection envelope, the control system monitors pilot commands resulting in the pilot always being able to get the maximum performance out of the aircraft without risking going over safety margins.
Flight control movements are converted to electronic signals that are transmitted by a system of wires, hence the term fly-by-wire. The actuators at each control surface are determined by flight control computers to provide the ordered response. Fly-by-wire aircrafts include a system that automatically sends signals to computers to perform functions independently of the pilot’s input, the same goes for systems that stabilize the aircraft in an automatic fashion.
Although fly-by-wire systems are rather complex, one can explain their operation in simple terms. When the pilot moves the sidestick, a computer receives a signal. The signal is sent through various channels or wires to make sure that the computer receives the signal. The term Triplex refers to the operation where three channels are in use. In an analog system, the signal is sent to the computer, which performs a calculation and adds an additional channel. The Quadruplex signals are then received by the control surface actuator and the surface starts to move. The computer receives a signal back from the potentiometers in the actuator reporting the position of the actuator. Once the actuator has reached the desired position, the incoming and outgoing signals cancel each other and the actuator stops moving, thus completing a feedback loop. In digital fly-by-wire flight controls, complex programs interpret digital signals form the pilot’s control input sensors and perform calculation based on the flight control laws programmed into the flight control computers and input from the air data reference units and other sensors. Finally, the computer sends commands to the control surfaces to adopt a configuration that will put the flight on the desired path.