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Fly-by-wire

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Fly-by-wire AI simulator

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Fly-by-wire

Fly-by-wire (FBW) is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals, and flight control computers determine how to move the actuators at each control surface to provide the ordered response. Implementations either use mechanical flight control backup systems or else are fully electronic.

Improved fully fly-by-wire systems interpret the pilot's control inputs as a desired outcome and calculate the control surface positions required to achieve that outcome; this results in various combinations of rudder, elevator, aileron, flaps and engine controls in different situations using a closed feedback loop. The pilot may not be fully aware of all the control outputs acting to affect the outcome, only that the aircraft is reacting as expected. The fly-by-wire computers act to stabilize the aircraft and adjust the flying characteristics without the pilot's involvement, and to prevent the pilot from operating outside of the aircraft's safe performance envelope.

Mechanical and hydro-mechanical flight control systems are relatively heavy and require careful routing of flight control cables through the aircraft by systems of pulleys, cranks, tension cables and hydraulic pipes. Both systems often require redundant backup to deal with failures, which increases weight. Both have limited ability to compensate for changing aerodynamic conditions. Dangerous characteristics such as stalling, spinning and pilot-induced oscillation (PIO), which depend mainly on the stability and structure of the aircraft rather than the control system itself, are dependent on the pilot's actions.

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.

Side-sticks or conventional flight control yokes can be used to fly fly-by-wire aircraft.

A fly-by-wire 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; more for a maneuverable fighter), which means that the stability surfaces that are part of the aircraft structure can therefore be made smaller. These include the vertical and horizontal stabilizers (fin and tailplane) that are (normally) at the rear of the fuselage. If these structures can be reduced in size, airframe weight is reduced. The advantages of fly-by-wire controls were first exploited by the military and then in the commercial airline market. The Airbus series of airliners used full-authority fly-by-wire controls beginning with their A320 series, see A320 flight control (though some limited fly-by-wire functions existed on A310 aircraft). Boeing followed with their 777 and later designs.[citation needed]

A pilot commands the flight control computer to make the aircraft perform a certain action, such as pitch the aircraft up, or roll to one side, by moving the control column or sidestick. 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. The controllers measure the position of the flight control surface with sensors such as LVDTs.

Fly-by-wire control systems allow aircraft computers to perform tasks without pilot input. Automatic stability systems operate in this way. Gyroscopes and sensors such as accelerometers are mounted in an aircraft to sense rotation on the pitch, roll and yaw axes. Any movement (from straight and level flight for example) results in signals to the computer, which can automatically move control actuators to stabilize the aircraft.

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flight control system utilizing electronic interface
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