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Yaw Damper... What Exactly Is It?  
User currently offlineGulfstreamGuy From United States of America, joined Jul 1999, 646 posts, RR: 1
Posted (10 years 9 months 2 weeks 3 days 9 hours ago) and read 31785 times:

Saturday, our NW flt 5807 (CRJ) LIT-DTW was canceled because a "yaw damper would not engage", thus the plane had to be ferried to MEM for maintenance. I am a little fuzzy on the understanding of what it exactly does.

Any help?

Thanks,
GulfstreamGuy


"If we couldn't laugh, we would all go insane. " -Jimmy Buffett
5 replies: All unread, jump to last
 
User currently offlineB747skipper From , joined Dec 1969, posts, RR:
Reply 1, posted (10 years 9 months 2 weeks 3 days 9 hours ago) and read 31743 times:

Yaw damper is a gyro system which acts on the rudder(s), this for aircraft stability.
xxx
Have you ever heard about Dutch roll ??? (nothing against our friends from NL !)
Some (swept wing) airplanes are unstable on the yaw axis.
This because if they yaw to the left, the RH (swept) wing will present itself as a straight wing.
Straight wings create more lift, and more drag...
More lift = that RH wing will go up - More drag = RH wing is pulled aft (around yaw axis)...
Result, now, the RH wing being further aft, the LH wing will do that game...
LH wing will get more lift, more drag... result is the aircraft will yaw L and R.
Result could be a loss of control = Dutch roll.
xxx
So the yaw damper prevents Dutch roll.
Generally, the yaw damper is the "3rd axis" of the autopilot.
Modern airplanes generally have a full time "series" yaw damper, engaged at all times.
Some airplanes being unstable, their yaw damper is a "NO GO item" on the MEL.
Some other airplanes may be limited in speed and altitude if yaw damper is INOP.
The 747s have 2 yaw dampers... But the airplane flies perfectly without them. Not a NO GO item for 747s.
xxx
Hope this helps you...  Smile
(s) Skipper


User currently offlineGulfstreamGuy From United States of America, joined Jul 1999, 646 posts, RR: 1
Reply 2, posted (10 years 9 months 2 weeks 3 days 9 hours ago) and read 31726 times:

Thanks B!

Now I can act like I knew what that meant all the time when someone asks me! Big grin

GulfstreamGuy



"If we couldn't laugh, we would all go insane. " -Jimmy Buffett
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 3, posted (10 years 9 months 2 weeks 3 days 5 hours ago) and read 31684 times:

The yaw damper system isn't exclusively based on "gyro" systems. It also receives yaw acceleration information, often from an internal liquid base yaw acceleration sensor.

The yaw damper offsets the rudder in proportion to the roll angle. It also "kicks" the rudder pedal in response to yaw acceleration to provide a smooth flight and offset the effects of dutch roll as mentioned.

In some aircraft, typically the smaller ones, the yaw damper is required equipment. If it is unservicable, the aircraft may be subject to operating restrictions in speed and/or altitude. This is primarily due to the descision to use a smaller (low drag) vertical stabilizer that just isn't efficient at high altitudes without some help from the yaw damper. Of course the 747 could never be accused of having a small tail....

According to the CRJ MMEL, only the -700 and -900 variants require an operational (1 out of 2) yaw damper for dispatch. The 100/200 doesn't.

http://www.tc.gc.ca/aviation/applications/mmel/en/mmel.asp?x_lang=e





User currently offlineAC_A340 From Canada, joined Sep 1999, 2251 posts, RR: 1
Reply 4, posted (10 years 8 months 3 days 19 hours ago) and read 31390 times:

Though the CRJ may not require operational yaw dampners, some airlines do opt to include it in the MEL. I have heard that the CRJ is really hard to fly without this system. I know for sure that one of the systems needs to be operational in order to engage the autopilot. The Citation 10 has 3 of the systems because the aircraft is so susceptible to Dutch Roll.

User currently offlineDC-10tech From United States of America, joined Jun 2001, 298 posts, RR: 2
Reply 5, posted (10 years 8 months 3 days 15 hours ago) and read 31348 times:

ON the DC-10/MD-11, yaw damp is a no go. There are four independant channels, two for the upper rudder and two for the lower. At least one (at some companies, one for each rudder) must be functional.


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