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Guest ScottPilot

When to use yaw damper?

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Could someone please tell me when/how the yaw damper on the 737 autopilot should be used. What does it do and what happens if you don't use it?Thanks barry

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In the real world B737 the yaw damper is engaged all the time.If you loose it at high altitudes and at high airspeeds a phenomenon known as 'Dutch Roll' can occur. Dutch roll happens on swept wing airplanes when a slight yaw upsets the airplane. The yaw causes the forward moving wing to increase lift more than the retarding wing. This in turn causes a rolling moment. At some point of the sideslip caused by the yaw , the vertical stabilizer counteracts the yaw and creates a yawing motion in the oppsite direction. Now the whole game repeats itself in the other direction. These oscillations increase progressively. This is then known as Dutch Roll, similar to a sailing ship rolling in rough sea.The yaw damper senses the minute yawing motions and counteracts them by applying tiny amounts of opposing rudder deflections, before they become a problem.Hope this helps.

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Yes, it is true that the yaw damper is engaged on the 737 all the time, but on many other aircraft, including other jets, the yaw damper is normally disengaged on approach.I have flown Falcon 20's for many years, and it is normal procedure to disengage the yaw damper when the approach flaps are set. On the older Falcons this is done manually by the pilot and in the newer Falcons, this occurs automatically.On these airplanes, as well as many other smaller aircraft, leaving the yaw damper on during approach can compromise directional (yaw) control, since the yaw damper is integrated to the rudder servos or rudder control mechanisms, usually tied through the autopilot system.In these aircraft, (even the ones in flight simulator) you will notice that the rudder is not very responsive, and landing in a crosswind situation can be very difficult with the yaw damper engaged in those airplanes.So even though the 737 has its yaw damper engaged all the time, it must be compensating for the lower-speed flight on its own. In many other aircraft, like the Falcons, this is not the case, and the yaw damper must be disengaged for approach.The key is knowing the airplane that you are flying, and determining from the specs on that airplane when the yaw damper should be engaged or disengaged.Just another take on the use of a yaw damper.Happy Simming!Scott :-)ATP/CFII - In the real aviation world.

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>In the real world B737 the yaw damper is engaged all the >time. >If you loose it at high altitudes and at high airspeeds a >phenomenon known as 'Dutch Roll' can occur. Or worse. Since MS set dampings on its jets about 8X too high you don't need the Yaw Damper. Though, it does add even more 'damping' to Yaw. Further, the MSFS 'Yaw Damper' doesn't even work correctly. You can't get full rudder with it on. In fact, it is a mechanical damping device that only slows down the effect of rudder. I just sent Paul Golding updated flight dynamics for his B707 panel. This AC needs the Yaw damper ON during most flight or one will lose control at higher altitudes if he hits the rudder too hard. I've also seen it Dutch Roll with the Damper off. Which was a problem with the Real 707. While the 727 is easy to lose control of at altitude if the Yaw Damper is off. I aways warn the few people I send my flight dynamics files to that the Yaw Damper should be ON in the recent Jets I've done. Roll and Pitch dynamics are also significantly different from 'old school' MSFS jets. Ron

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