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FLY BY WIRE in other plane

Attilio Cardone

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Attilio Cardone



I know the difference between the normal law e direct law. I would like to know if even in other fly by wire aircraft there are both laws. For example, the 777 is a fly by wire: does the pilot input control the pitch, or is there a direct law, between the pilot controls and the aerodynamic surfaces, correct when using pitch or roll limits? Does the CS300 (a220) have a logic similar to airbus?

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Arto E.P. Karhu

In 777, the control law is somewhat similar to A320 except that they have added an artificial speed stability. Simplified, there is trim speed where the airplane is neutral in pitch, and it appears nose-heavy should the airspeed be under the trimmed speed and vice versa. The system compensates for small bank angles so that no constant back pressure is needed in modest turns. There are fallback modes not too unlike the ones in Airbuses, called Secondary and Direct modes. How the actual system is designed and constructed, is quite different from Airbus.

In Embraer E170/E190, the pitch and yaw controls are essentially analog electrical connections, simply replacing the wires. The gains of the system are adjusted as a function of various things, such as airspeed and angle-of-attack, in normal mode. In direct mode, they are not. The roll control is classic, with mechanical connections to the aileron and spoiler control actuators.

So, there are quite many rather different systems out there.

I don't know about the A220 series.

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