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Topic Author
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What Is Fly By Wire?

Fri Feb 16, 2001 12:48 pm

My guess is the controls are controled by electronics as opposed to cables.
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RE: What Is Fly By Wire?

Fri Feb 16, 2001 1:08 pm

Posts: 1665
Joined: Mon Dec 20, 1999 3:16 am

RE: What Is Fly By Wire?

Fri Feb 16, 2001 1:47 pm

It should be noted that controls, whether by electrical signal ( FBW ) or cables/linkage do not actually move the surfaces...( except some controls on some Douglas aircraft that use cables to directly move aerodynamic control tabs ). The muscle that actually moves the surface is hydraulic pressure. Cables/linkage or electrical signal ( via an EHSV ) merely port pressure to the required side of the actuator piston.
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RE: What Is Fly By Wire?

Fri Feb 16, 2001 10:01 pm


You have answered your own question. With all of the fat rendered out of an explanation... Beginning at the control surface and working to the cockpit, basically a fly by wire aircraft has the control surface connected to the actuator which is connected to a microprocessor. No cables and pullies to the yoke or stick in the cockpit.


RE: What Is Fly By Wire?

Sat Feb 17, 2001 8:00 am

I believed that fly by wire meant that you can actually control a plane only by using the turbines, by increasing or decreasing thrust.
This since the accident at sioux city.

Maybe im wrong.
Best Regards.
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RE: What Is Fly By Wire?

Sat Feb 17, 2001 4:54 pm

This is true fly by wire
Behind every "no" is a "yes"
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Joined: Sat Oct 25, 2003 1:58 am

RE: What Is Fly By Wire?

Sun Feb 18, 2001 1:01 am

Conventional control systems in most large transport aircraft, have control cables connecting the control column, control wheel and rudder pedals, connected to the power control units (the hydraulic acutators the move the control surfaces). The cables move valves in the PCU to control the flow of hydraulic fluid.

When the autopilot is engaged, the mechanical valve in the PCU is over-ridden by an electrically controlled valve controlled by the autopilot.

Some PCUs are mounted on a pivot so that in the case of a hydraulic failure, the pilot can still move some control surfaces without the hydraulic assist.

Fly-by-Wire systems remove the control cables but retain the PCUs. Control is exclusively electrical. Additional redundency is required to give these systems the same operational safety as the conventional systems.

Fly-by-wire systems can be integrated with a computerized flight control systems much easier than the conventional system. In turn, computerized flight control systems can arguably be programmed to make flying the aircraft simpler. Without an integrated computerized flight control system, many military aircraft like the F-16 would be almost impossible to fly due to the inherent instability designed to make the aircraft agile.

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