Unsourced material may be challenged and fly by wire system in aircraft pdf. Both systems often require redundant backup to deal with failures, which increases weight. The term “fly-by-wire” implies a purely electrically signaled control system. It is used in the general sense of computer-configured controls, where a computer system is interposed between the operator and the final control actuators or surfaces.
This modifies the manual inputs of the pilot in accordance with control parameters. Fly-by wire systems are quite complex, but their basic operation is fairly simple. The flight control computer then calculates what control surface movements will cause the plane to perform that action and issues those commands to the electronic controllers for each surface. The controllers at each surface receive these commands and then move actuators attached to the control surface until it has moved to where the flight control computer commanded it to. This process is repeated continuously as the aircraft is flying. Fly-by-wire control systems allow aircraft computers to perform tasks without pilot input.
Automatic stability systems operate in this way. CCV controls compensating for the lack of natural stability. Any failure will be indicated to the crews. A FBW aircraft can be lighter than a similar design with conventional controls. This is partly due to the lower overall weight of the system components, and partly because the natural stability of the aircraft can be relaxed, slightly for a transport aircraft and more for a maneuverable fighter, which means that the stability surfaces that are part of the aircraft structure can therefore be made smaller. If these structures can be reduced in size, airframe weight is reduced. The advantages of FBW controls were first exploited by the military and then in the commercial airline market.
Boeing followed with their 777 and later designs. Electronic systems require less maintenance, whereas mechanical and hydraulic systems require lubrication, tension adjustments, leak checks, fluid changes, etc. Placing circuitry between pilot and aircraft can enhance safety. For example, the control system can try to prevent a stall, or it can stop the pilot from over stressing the airframe. The main concern with fly-by-wire systems is reliability.
While traditional mechanical or hydraulic control systems usually fail gradually, the loss of all flight control computers could immediately render the aircraft uncontrollable. A “mixed” control system such as the latter is not desirable and modern FBW aircraft normally avoid it by having more independent FBW channels, thereby reducing the possibility of overall failure to minuscule levels that are acceptable to the independent regulatory and safety authority responsible for aircraft design, testing and certification before operational service. Long runs of mechanical and hydraulic connections were replaced with wires and electric servos. The programme was curtailed when the airframe ran out of flight time.