Autopilot control systems

[doonesbury]

To all tech headsa out there,

I am currently an electrical engineering student doing a double major in power and control systems. I am starting a 5th year research project looking at the autopilot control systems that are used when their is an engine loss on aircraft like the 777 or 330.

Specifically the systems that allow controlled flight in a situation where there is considerable yaw due to the huge thrust differential between port and starboard engines if one fails or is siginificantly reduced in power.

The computer control units that run such things are obviously quite significant within a system and of continued interest for developers of such systems.

I was hoping that any of you with any knowledge, specific or general, would be able to provide me with details of the systems in the 777 0r 330 ( i am looking at these aircraft in particular as they have such large engines that one engine going down can make the aircraft virtually unfliable with out assistance from the autopliot). Things like, number of input sensors, how often system corrects, limits of system, how long does it take for system to settle, how much control the system allows the pilot to have. Any of these or other bits of information that you might think useful would be appreciated.

If the information is a little complex to be posted here, you can email me at this address

[email protected]

Any information will be acknowledged and copies of the fianl report will be provioded to anyone who would like one.

Cheers

Doonesbury

PS. I am posting this in both in the tech log and the rumour and news forums so as many people as possible see my request and can reply

thanks again
doonesbury

[spannersatcx]

My understanding is that the 777 rudder auto kicks over on eng/thrust loss. How it happens I'm not in the know,try the boeing website at http://www.boeing.com
As far as I know the 330 doesn't have a similar thing just yaw damp systems maybe worth trying the bus website at http://www.airbus.com
Sorry I can't be of much more help don't have access to manuals as I'm enjoying a well earned couple of weeks rest.


[This message has been edited by spannersatcx (edited 27 August 1999).]

[Genghis the Engineer]

I'm sure you know this already, but the system is basically a negative feedback SAS, which takes sideslip angle as it's input and rudder angle as it's control. A Bank angle SAS will sort out the resultant roll (in fact it's all wrapped up in a complex feedback and control matrix, but this is a fair approximation)

The pilot / autopilot will also make use of a term called VMCA (minimum control speed in the air) - so long as the aircraft stays above that the rudder is able to hold the yaw due to failure of the most critical engine.

If you want a good book on the subject, try "Automatic Flight Control Systems" by Donald McClean (although watch out for the above average number of arithmetic errors in the worked examples).