Yaw Dampener: Pilot rudder input

[jpilotj]

Good day,

I recently read in the King Air magazine that gets delivered to my place of work that the Yaw Dampener is often mistaken as a device that omits the requirement for pilot rudder input (i.e the assumption is that the yaw dampener will always create a co-ordinated turn by the virtue of it cancelling any yaw). As the article stated however, this is not the function of the yaw dampener in entirety and input is still required to co-ordinate a turn, skid or slip condition.
I am therefore wondering what the requirement for rudder input is in larger jet aircraft. With the rudder being hardly ever used in flight in most normal circumstances is it the yaw dampener co-ordinating all turns?
If the yaw dampener is co-ordinating turns, why then does the normal axis remain at the pilots control with the auto pilot engaged. From my understanding the autopilot normal axis only activates on auto lands.

Thank you,

jpilotj

[Da-20 monkey]

Hi,

Here is an earlier thread about this:

http://www.pprune.org/questions/472694-flight-controls-jet-transports.html

From what I know a yaw damper is not an autopilot component like you say. A 737 for example only has a 2- axis autopilot. This is why a 737 has a crosswind limit for autolands, because It doesn't have the ability to kick off drift before landing.

[FlyingStone]

A 737 for example only has a 2- axis autopilot. This is why a 737 has a crosswind limit for autolands, because It doesn't have the ability to kick off drift before landing.

Some of the newer NGs have autopilots with fail-operational capability, which are 3-axis and add rollout capability to standard autoland operation.

From 737 FCOM:

The yaw damper system prevents unwanted (Dutch) roll and provides turn coordination.

737 isn't prone to Dutch roll, so yaw damper isn't a MEL item. It does provide turn co-ordination during normal operations, but the leg will still hurt after V1-cut - until you trim the aircraft :)

[bcgallacher]

The 747 Classics have a turn co-ordinating mode for the yaw damper system when the flaps are deployed. When the flaps are raised the system returns to yaw damp mode.

[gusting_45]

737 isn't prone to Dutch roll????

Flew 300/400 in the past with yaw damper inop in not very pleasant conditions and I can tell you for sure that it is.

[grounded27]

Just about all large jets have Yaw Dampers and most have triple axis autopilots. Several classic Jets had pneumatic, hydro mechanical units that used pitot pressure to restrict rudder movement. Most modern fly by wire aircraft use a number of inputs to dampen and coordinate/control turns along the yaw axis with an A/P engaged. Y/D and A/P control are often different components within the rudder actuator, commanded by flight control computers on separate channels using outside information such as accelerometers to help compute the commands.

The classic 727 had a crude yaw damper, I am surprised to hear the 737 did not.

[Al Murdoch]

Personally the only time I ever move the rudder pedals on the 737 is during landing and takeoff. And my turns are beautiful....

[jpilotj]

thank you everyone for your inputs

[Capt. Inop]

Some of the newer NGs have autopilots with fail-operational capability

From February 26 2003 and on the NG do have a fail operative autopilot.

The rudder channel (rollout guidance) and that kind of cat 3B stuff is an customer option.