Hello, When is rudder really required in a jet besides fixing a crab, engine failure, and steering? (Ex. steep banks, high angle of attack etc) I was doing some reading on Yaw Dampers and it said that the turn coordination function of the Yaw Damper is only active when the flaps are out. So if you wanted to turn a jet with flaps up would I need to coordinate the turn? I know that the Yaw Damper dampens Dutch roll but would it coordinated turns also when the Turn Coordination feature is off? If so why bother installing a separate feature that coordinates your turn with flaps down? Also does the turn coordination cut off when flaps are at 30 so sideslips can be done? Thank you :-wave

The ONLY Time to use Rudder in a jet is Engine Failure, TO/Landing Roll above 80 Knots and for Cross Wind Landing. The Yaw Damper and Flight Control Computers will keep the aircraft in co-ordinated flight.

What Mark said is correct, but let me just add a few points:The rudder can also be applied if the airframe is bent. Note, in this case rudder trim will be used as its quite a pain pushing those pedals over a long time (they are very very heavy).Turn coordination is not a function of flaps, but always "enabled". Forget MSFS's turn coordination / yaw damper function!On a real 767, you can always override the yaw damper's input (as long as its functioning) as its range is limited to a few degreees.Regards,Mark

Thanks for the reply, I just found a book on flying a 747 and it says quote "The Rudder also incorporates a turn coordinator which is programmed by selection of the flap to operate the Rudder automatically in the direction of turn as an aid in turning the aircraft at lower speeds" I also ran into a similar statement for the Airbus saying that its active when Flaps are out of the up position. That

If you want to learn some stuff on the use of Rudder in a jet, go to www.pprune.org and do a search for AA587. There is a lot of debate about the use of rudder in a large jet aircraft on that particular topic.

"Any info from the 767 manual would be greatly appreciated. Thank you"There is very little in our maintenance manuals which offer enlightenment on this subject, "November678x" (sorry, I've forgotten your real name).Speed, air impact pressure and other stuff go into the equation on the 767, but the manuals don't really tell you if the turn co-ordination is completely absent at high speed. Perhaps aircraft like the Classic 747 use flap settings to modify the "authority" of the yaw damping system. On the 767 and the 747-400, however, there is no direct flap input. Air Data Computers provide speed information and this affects the rudder deflection limits when movement is commanded by the Yaw Damper System (Rudder movement is normally limited at high speed by the Rudder Ratio System, but perhaps because of the way the Yaw Damper system hooks up with the rudder system, the Yaw Damper may require its own speed Vs rudder deflection programming(?)).Hope this helps anyway.Cheers.Ian.

Yes that helps :-), one last thing I could not find the answer to anywhere. If you turn right you get right rudder, so does the turn coordination provided by the yaw damper affect the side slip control application on landing? For instance if I have a right cross wind and I hit left rudder and right aileron just before touch down will the rudder try to oppose and go right since I applied right aileron? Also are the yaw dampers inactive on the ground so that controls can be applied for a crosswind? Thank you for your replies :-wave

>If you turn right you get right rudder, so does the turn coordination provided by the yaw damper affect the side slip control application on landing?I have been unable to find a definitive answer on this one. The Autoland system has a lot more authority than the yaw damper, so I initially thought that the interaction wouldn't create any problems. However, there was a comment by one person on the PPRuNe forum recently which made me think twice. He said, in so many words, that Yaw Damper authority is still significantly large not to ignore and that the Yaw Damper system should not fight against Autoland rudder control (or manual rudder input) in the first place (i.e. it should be smart enough not to fight other inputs). Unfortunately, there is nothing about this interaction in my books. Some have said, perhaps the Yaw Damper logic looks at "rate" rather than "magnitude" to determine the appropriate action for the situation (this I don't understand).>Also are the yaw dampers inactive on the ground so that controls can be applied for a crosswind?The Yaw Damper system is not active on the ground (it is inhibited).Hope this helps.Cheers.Ian.

I think someone should call up a designer at boeing and ask.. LOL Someone has to know the REAL answer to this one..

>I think someone should call up a designer at boeing and ask..555-BOEINGAnyone got a dime? :-)