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scottb613

Skidding Turns...

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Morn'n all... quick question - while performing some VFR pattern work to increase my landing performance - I noticed the plane really skids around turns... I believe I have the yaw damper on... Should this be the case or am I doing something wrong ??? I did some coparison with later model 737's by POSKY and KITTYHAWK - which do not have this problem... Thanks for this great plane !!!Regards,Scott

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>Morn'n all...>> quick question - while performing some VFR pattern work to>increase my landing performance - I noticed the plane really>skids around turns... I believe I have the yaw damper on...>Should this be the case or am I doing something wrong ??? I>did some coparison with later model 737's by POSKY and>KITTYHAWK - which do not have this problem...>> Thanks for this great plane !!!>>Regards,>ScottI noticed the same thing although mine slides into the turn. YD is on here also but something has changed from V1.1 in regards to the YD. The YD indicator shows proper rudder deflection during the slide as well.Cheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.sstsim.com/images/team/JR.jpgwww.SSTSIM.com

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Here is a dumb question but what is the yaw damper user for and should it always be turned on? I always have it turned off. When I trun it on, the rudder starts to shake epecially during taxi.Thanks,Bill

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>Here is a dumb question but what is the yaw damper user for>and should it always be turned on? I always have it turned>off. When I trun it on, the rudder starts to shake epecially>during taxi.>>Thanks,>>Billhttp://en.wikipedia.org/wiki/Yaw_damperA little more technical:http://www.boeing-727.com/Data/systems/infoyawdampers.htmlOn an aircraft like the B737, the yaw damper is usually left on all the time but that depends on the airline. They are always on in the air though. On a real aircraft, the yaw damper does not cause the rudder to shake. In MSFS that's just a side effect of the poor implementation of a Yaw Damper by MS.Cheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.sstsim.com/images/team/JR.jpgwww.SSTSIM.com

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Just wondering if the slipping turn and lack of a YD problem could be caused by the use of the Steering Tiller Axis in FSUIPC?As it stands, the FD's make it almost impossible to fly manually as the slip is so drastic. Especially at approach speeds.Cheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.sstsim.com/images/team/JR.jpgwww.SSTSIM.com

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OK, before we get too far off on a tangent here, there were no changes to the FDE in V1.2 that would affect yaw performance. The only FDE changes were to disable the default autospoilers and a change to one of the engine thrust curves to correct some very cold wx anomalies.There is a known issue with yaw/slip performance in the FDE, and we're looking at it. The FSUIPC Steering Tiller axis is not used by the panel. Since V1.1 the YD is internally disabled by the panel when on the ground, even when turned on in the panel, so there should be no rudder flutter on the ground. If you have a noisy rudder axis with too small a dead zone when centered, you could be seeing the effects of that noise.RegardsBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

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An update to the FDE will be released in the V1.22 update in the next few days. That should put this one to bed.RegardsBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

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nice one bob!but there is a thing now....Why flight simmers think that YAW DAMPER make EVERY TURN coordinated?'cuz EVERY FM that I've readed, YAW DAMPER is to neutralize the Dutch Roll.but, there are things that even God don't know how to answer, eh? :-sae

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>>Why flight simmers think that YAW DAMPER make EVERY TURN>coordinated?>'cuz EVERY FM that I've readed, YAW DAMPER is to neutralize>the Dutch Roll.Because the yaw damper does coordinate turns on the 737 and all other larger aircraft as well as provide Dutch Roll protection. The Yaw Damper relies on a gyro oriented to sense changes about the vertical axis. If it senses anything but a steady state it will add rudder to correct or null the gyro. This includes skids or slides in turns which is a form of turn coordination. There are really only four flight regimes in the 737 that require use of rudder. Otherwise the pilots feet are planted firmly on the cockpit floor.1. Takeoff2. Landing 3. Crosswind de-crab(at flare)4. 1 engine out flightCheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.sstsim.com/images/team/JR.jpgwww.SSTSIM.com

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>>>>Why flight simmers think that YAW DAMPER make EVERY TURN>>coordinated?>>'cuz EVERY FM that I've readed, YAW DAMPER is to neutralize>>the Dutch Roll.>>Because the yaw damper does coordinate turns on the 737 and>all other larger aircraft as well as provide Dutch Roll>protection. >so, this maybe need a rewrite, eh?Boeing AFM, Volume 2, 13.20.08Yaw DamperThe yaw damper system consists of a yaw damper coupler, rate gyro, and a yaw damper actuator in the rudder power control unit.The rate gyro sends yaw change signals to the yaw damper coupler. The coupler responds only to those yaw rates which are associated with dutch roll.Command signals are then sent to the rudder power control unit to deflect the rudder. The yaw damper has no turn coordination function. No rudder pedal movemnt results from Yaw Damper operation.(...)---Bob may confirm, or another user with the system manual of a 737.>The Yaw Damper relies on a gyro oriented to sense changes>about the vertical axis. If it senses anything but a steady>state it will add rudder to correct or null the gyro. This>includes skids or slides in turns which is a form of turn>coordination. >As said above, this is not true, in the 737.

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In most transport category airplanes, the yaw damper does both dutch roll damping and turn coordination. It's primary function is to keep yaw rates out of the resonant yaw rate band that produces unstable dutch roll. However, most, if not all, modern digital yaw damper controllers use a washout or similar function in combination with the dutch roll damping function that, in effect, dials down the yaw rate input gain as a function of the bank angle, thus injecting a sort of false stimulus to the system that looks like a yaw towards the turn, and resulting in the yaw damper making a rudder input into the turn. Net result is approximately coordinated flight in turns without a pilot rudder input (except in those cases when the yaw rate lies within the dutch roll filter bandwidth).CheersBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

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according two pilots, the 737 classic AP cannot make yaw controls (control only two axis), and the yaw damper system do not make imputs for rudder to coordinate the turn.the same is not valid for the 737 NG.The pilot must pave the aircraft for the side of the turn in the beginning of the same one to neutralize the sideslip. The resultant lift in vertical fin make the rest of job.But in cruise, usualy the pilot do not pave to avoid a over control.

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Hi BOB... THANK YOU - SIR - you just keep making a great package better !!! Looking forward to seeing your magic... I wish someone would put this kind of attention into the DC-10 by SGA... Have you seen the latest repaints by Mr. Idone ??? Works of art... Gotta love this old tin...Regards,Scott

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>>>>>>Why flight simmers think that YAW DAMPER make EVERY TURN>>>coordinated?>>>'cuz EVERY FM that I've readed, YAW DAMPER is to neutralize>>>the Dutch Roll.>>>>Because the yaw damper does coordinate turns on the 737 and>>all other larger aircraft as well as provide Dutch Roll>>protection. >>>so, this maybe need a rewrite, eh?Um, I don't think so! I will however change my wording to say that the Yaw Damper(YD) doesn't provide Auto Coordination but it does provide passive coordination.>>Boeing AFM, Volume 2, 13.20.08>Yaw Damper>>The yaw damper system consists of a yaw damper coupler, rate>gyro, and a yaw damper actuator in the rudder power control>unit.>>The rate gyro sends yaw change signals to the yaw damper>coupler. The coupler responds only to those yaw rates which>are associated with dutch roll.>Command signals are then sent to the rudder power control unit>to deflect the rudder. The yaw damper has no turn coordination>function. No rudder pedal movemnt results from Yaw Damper>operation.>>(...)>---Thank you for the reference. Is that from a current up to date 737-200 manual. Both my training, MM and up to date Boeing FM don't say that one particular term. Even our flight training department says feet off the pedals unless you are taking off, landing or have an engine out.>>Bob may confirm, or another user with the system manual of a>737.As a 737 mechanic I have access to those manuals and know the system very well.Yaw Damper Coupler 101.The YD, as I said before, contains a rate gyro that senses deviations about the vertical axis. The Coupler also receives airspeed data from the DFDC(Digital Flight Data Computer) which allows the Coupler to determine the amount of rudder deflection based on airspeed. Slower = more deflection, faster = less deflection. The Coupler has no idea as to what the upset to the vertical axis was, so it reacts to ALL yaw events except those that are input by the pilots. A yaw event during a turn WILL get nulled by the Yaw Damper. A yaw event could be a gust, slip or skid as long as the later 2 are not pilot induced through rudder pedal input.I will however say thet the YD is Reactive to yaw events and doesn't provide an initial kick of the rudder into a turn like the 747 does. It does however sense and eliminate yaw deviations in the turn and the roll spoilers have a great effect on eliminating adverse yaw on initial entry into a turn.>>>The Yaw Damper relies on a gyro oriented to sense changes>>about the vertical axis. If it senses anything but a steady>>state it will add rudder to correct or null the gyro. This>>includes skids or slides in turns which is a form of turn>>coordination. >>>As said above, this is not true, in the 737.>Yes it is. I stated it was a FORM of turn coordination and not active turn coordination. It reacts to yaw events, which also happen to be slips and skids. Have you been on the flight deck and watched the YD indicator in a 30 degree banked turn? Trust me the ball is centered and the YD is working to help do this.The YD is a very stupid system, in terms of operation, so to speak. It WILL correct any unintentional yaw event.I'm sure you will disagree with all I've said here but afetr 24 years in aircraft maintenance I feel I've picked up a few things here and there. :-waveCheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.sstsim.com/images/team/JR.jpgwww.SSTSIM.com

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Hi Gustavo; Not sure what you mean by "pave" here. The best info I have says that in 1999 the FAA issued AD 97-14-03, requiring operators to comply with Boeing Service Bulletin 737-27A1206, which included a new digital yaw damper as part of a number of safety improvements to the rudder control system. I did find this SB referenced in Boeing OMB TBC-13, dated 3 Dec 1999, which is part of one of the flight manuals I have for the -200. The guys I'm talking to say the -200s they fly do indeed fly coordinated turns without use of rudder pedal inputs due to the yaw damper. Maybe the pre-AD jets didn't...don't know.CheersBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

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V1.22 update now released to address this issue. A link to the file can be found in the FAQ.RegardsBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

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Bob, V1.22 is a great little update - it's an absolute joy to fly now! Thank you for your ongoing work on this project, every new version seems like one step closer to perfection :) Oh, and a question for the pros: In the 732, would I disengage the yaw damper for a crosswind landing? It seems that I can only get sufficient rudder authority for a wing-low landing when the Y/D is off (I tested this with a 20kts x-wind component).Kind regards,Holger

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Holger; In the real world, no, but in FS the yaw damper will get in the way on a strong x-wind landing. That said, I may have a trick up my sleeve that can fix that.RegardsBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

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