Stupid, The Yaw Damper system maintains the aircraft's Stability and turn Coordination during flight and works with the the IRS system. In the real bird you would not feel the yaw damper movement in the rudder pedals. The colors represent the hydraulic systems respectively, center, right and left in case of failer you will have backups :]. I'm sure you can figure out how this helps the pilot workload etc?Best Wishes,Randy J. [email protected]" A little learning is a dangerous thing"

Now, stupid idiot, I know it's been six years since I've flown a 172 for the last time, and to my knowledge, v/s hardly ever gets over 600 fpm in that thing, but I do not see your aversion to climbing or descending at 4000 fpm.It's all in the initiation of the maneuver. As I understand from ex-737 pilots, FLCH can be quite drastic in the 737. But in the 757 and 767, everything is super smooth. So instead of a 2-g pull or 0-g dive, it's all rather smooth.And since in real life, flight planning is done with FLCH and all fuel calculations in the flight plan are done using normal procedure climb and descent (ie. FLCH or VNAV which will operate identical most of the time), I don't want to start burning extra fuel by climbing and descending uneconomically.Did you know that starting a descent 5-10 minutes early and and having to stay low the whole time, resulting in some level flight at low altitudes, as happens often in the approach to large airports, can cost your more than a metric ton of EXTRA fuel used? Imagine yourself not being able to go up to optimum cruise level on your short flight since it wasn't available and you had to stay 4000 ft lower, now you're almost cutting into your legal final reserve fuel.So as far as pax comfort goes, FLCH is fine. Whatever you want to do on your computer is up to you, just telling you like it is.Happy simming!Iz

"Theres no yaw damper for the cessna 172"No s..t!...but you can certainly learn about Yaw in a C172, then when you add the word 'damper' to the sentence, it all falls in to place.;-)

now thats a nice and great explanation...thanks:)but what i still don't understand is why yaw motions happen on their own? or do they even happen? I guess its got more to do with aerodynamics right?I understand the part about helping out to make perfectly coordinated turns though.hey iz, i guess u read me wrongly, or there's a problem with my english :), but anyway i was referring to 767 when i say excessive climb rates. Hmm its quite possible to climb at over 4000 fpm with a low ZFW and low fuel... No doubts about that.And uh,HAPPY SIMMING

"but what i still don't understand is why yaw motions happen on their own? or do they even happen? I guess its got more to do with aerodynamics right?"Side gusts hitting a stabilizer will make the aircraft yaw. On some (longer) aircraft, such as the 747 and the 767-300, it will actually make the fuselage bend/flex. The function of the Yaw Damper Computer which handles fuselage bending is called "Modal Suppression" (don't ask me what Modal means :-hah).Accelerometers are placed at the front and back of the aicraft.. and the sensed side acceleration forces produce electrical signals which are fed into the Yaw Damper Module and compared. The rudder is made to move to suppress the bending.Hope this helps.Cheers.Ian.

re: yaw motionsIan's fine explaination aside, yaw motions are a by product of swept wing aircraft. They tend to have stronger yaw stablility than roll stablility. In other words if yawed and rolled in one direction, swept wing aircraft will correct back to neutral faster in yaw then in roll. Actually, what occurs is a yaw is induced, due to turblence or pilot imput. The wing on the side as the direction of the yaw will be retreating and the opposite wing will be advancing. The advancing wing has greater lift as result and a roll is induced. The opposite occurs on the retreating wing. So a roll occurs in the direction of the initial yaw. However, now the strong yaw stablility forces the nose back in the opposite direction, so much so, that it probably overshoots center and begins a yaw in the opposite direction. The airplane begins to correct the roll from the original yaw but more slowly. What results is a motion where the aircraft is rolling in one direction and yawing in the opposite. The is called Dutch Roll and is a charactoristic of most swept wing aircraft.The yaw damper is device either independent of or a function of the autopilot system. It has an accelerometer that senses slight yaw movements and applies rudder to correct them before the roll motion is initiated. A side function is that the yaw damper coordinates all turns. On many aircraft a yaw damper is a dispatch requirement (Learjet 20's, 35, 55, B-727) and if it fails in flight, maximum altitude limits are imposed.Iz, nice discusstion on V/S verses FLCH and VNAV. I can attest to the smoothness issues of FLCH in pitch. V/S can be more smooth in pitch control in our Lear 45, but like you implied, someone needs to be watching what's going on as it can mask performance problems. Automation is good at that.Personally, I use FLCH as much as circumstances allow for climb, VNAV for descent, V/S for small (1000 - 4000 ft) altitude changes at altitude and for mach climbs in turbulence and temperature fluctions. Below 10000, FLCH nearly exclusively.My two cents worth.Rich Wichita KS

If im not wrong the Yaw Damper must be disengage at take off, final approach and taxing. And should be engage at high altitudeJose Rafael NavarroYV

Unfortunately, you are wrong indeed! The yaw damper is ALWAYS on during normal ops. When we arrive at the airplane it's on and when we leave again, it's still on, it stays on all the time.Iz

On the older Learjet, that's true, the Yaw Damper must be off for takeoff and landing. Actually, the AFM says must be on immediately after takeoff and remain engaged until the landing flare. One landing with it one and you knew better the next time to get it turned off! Later Learjets could land with the yaw damper on as the torque was reduced when flaps were extended beyond 25 degrees. The newest Learjets, the yaw damper is engaged after takeoff and remains on for the remainder of the flight. Larger, more modern aircraft like the B767 have yaw dampers that work differently than in the Lear since hydraulic controls are involved. In those systems, the yaw damper is engaged on preflight and never touched again. This was the case in the 600/601 Challenger.Different aircraft, different ways of doing things!Rich

"The newest Learjets, the yaw damper is engaged after takeoff and remains on for the remainder of the flight.'Do you mean it is switched on, manually, after takeoff, Rich? What happens on landing. Is it automatically disengaged?"Larger, more modern aircraft like the B767 have yaw dampers that work differently than in the Lear since hydraulic controls are involved. In those systems, the yaw damper is engaged on preflight and never touched again."The 767 Yaw Damper is actually "armed" before takeoff (with the switches).... even though the switches say "ON". The engagement only comes after takeoff: It has a 5 second "fade in" which prevents sudden rudder actuation). Similarly for landing, it takes 5 seconds to fade out.Hope this helps.Cheers.Ian.P.S. Thanks for the mini-tutorial on Yaw Damping :-)

Hi Ian,Nice to chat with you again. Been away from the PS1 board for awhile.Yep, yaw damper is engaged with a switch just after gear retraction and clicked off with the control wheel master switch in the flare. That's for the early Learjets, as well as the 1124 Westwind and Na265 Sabreliner that I've flown. Later ones, you could land with the Y/D engaged as the torque was reduced when flaps were extended to the landing setting (beyond 25 degrees). The Challenger was a fade-in/fade-out sytem. In fact there was some discussion on another chat site about just how that system did work for landings.When I say modern aircraft, I have to be careful. Our Lear 45 still requires engagement of the Y/D after takeoff (it's not required for flight, but for passenger comfort, we get it one as soon as possible) and remains engaged throughout the flight and through landing. The problem is that is doesn't fade out on landing, so most of the time I kick it off with the control wheel master switch about 500 ft AGL. That way, in a stiff Kansas crosswind, I'm not fighting the Y/D when I try to take the crab out when landing. Yes, we do the ol rudder straight & wing down crosswind landing method. I don't think that's works well with the Boeing's with podded engines!Take care Ian,Rich

Howdy Rich,Actually, that method of crosswind landing works quite well in the 757, I use it all the time, just like the autoland will start decrabbing at 500'RA. I find it a nice and stable way to land with a gusty crosswind, much more so than kicking the nose straight in the flare. It also relieves me of having to aim my butt on the upwind side of the centerline with a crab angle!Embraer Brasilia I flew before this also had a YD which is only used between takeoff and landing. Kicking off the YD was done with the same yoke switch as the AP (dual stage switch).Iz

"That way, in a stiff Kansas crosswind, I'm not fighting the Y/D when I try to take the crab out when landing."Interesting... Just wondering what authority the Lear Yaw Damper has. The 767 only has a few degrees (+/-6 max) compared with full rudder authority (26deg max).Cheers.Ian.