sorry for not declare the problem

sorry for not declare the problem,
am a student in the aerospace engineering
department,and i love the plc tech. very much,
so,i want to make my graduating project using the plc in controlling the aircrafet control systems.
actually i need an aidea in using the plc in the plan control systems

Thanks for coming back with a more clearly stated question. We like to help students here, but an amzing number aren't willing to put in the effort to get that help.

It is my understanding that the stealth bombers, which are fly by wire, actually use micro-PLCs for operating some of the flight control surfaces. The pilot sends a supervisory command, but because the planes are not inherently stable, and the pilot reaction time is insufficient to maintain proper control, a number of small PLCs are used to move the appropriate aeleron on whatever. I expect the inputs are from pressure sensors, temp sensors, pitch sensors, etc. You would know more about that than I would. The PLC otuputs to actuatators then make the adjustments as required.

Let your imagination run a bit, with this as a starting point, and see what else you can come up with.

Fly By wire

Yes Tom you are correct. The Apache helicopter as well as the comanchee also use the same technology. The system in the Apache is very similar to any encoder. The pressure signal is sent to the controller, it factors the set output position based upon external readings (altitude, temp, cross wind, ect) then sends control pulse to the servo motor(hydraulic valve) with small encoder on it relaying position back to the controler. The Apache can also maintain the an exact hover without any input from the pilot based on the same system.

Sparky,

Something thats always interested me,
Are the Apache's PLC off the shelf models and if so, what brand?
Also, what happens when one of them hangs up? Hopefully something other than a crash.
I want to build a plane one day, but so far was not planning on using a PLC for it's control.

Regards,

Doug

Off the shelf

I'm sad to say nothing on the Apache (short of nuts and bolts) is off the shelf. Lockheed-Martin makes most of the electronics as well as Rockwell Int. Due to space and weight constraints most units are designed specifically for each aircraft model. The internals are real close to the same, as you would find in any I/O processor unfortunately they are not easily programmed. You best bet would be to purchase flight control components from an aeronautical distributor.