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How much help is a yaw damper?

They are common on longer hulls, starting (in light GA) with the PA46.

The system involves a yaw gyro and an autopilot-like servo which drives the rudder, with a very limited amount of movement. It is thus not very light, adding perhaps 10kg, and not cheap, costing maybe €10k.

Since yaw is a secondary effect of roll (and vice versa) I wonder whether the more common IFR tourers would not benefit from a YD too, in turbulence in which the "snaking" motion is obvious in all GA types in which I have ever flown. This motion cannot be countered with ailerons.

I have read some very scathing comments on the idea (in the shorter hulls of light IFR tourers) but the fact is that none of the people writing them could possibly know for real.

A YD is technically an option on the KFC225 which was fitted to post-year-2000 TB20/21s. It could also be fitted to earlier autopilots. A while ago, I saw a post on the Socata owners' group from a man who bought a TB20/21 with a YD installed, in the USA. I tried to find out from him how well it worked but the correspondence was inconclusive. I got the feeling he did not know what it did.

Very considerable paperwork issues aside, could a yaw correction signal be derived from an AHRS heading gyro such as the Sandel SG102? A yaw is a heading change, after all.

Shoreham EGKA, United Kingdom

I never use mine. I don't think it does much at all on a PA-46 from a cockpit point of view. Apparently it does help the passengers a bit though.

EGTK Oxford

I think it depends on the airplane. The Cessna 340 and the Piper Navajo Chieftain I sometimes fly both have yaw dampers and they make a big difference, particularly for people sitting in the aft row of seats.

As for singles I have only flown 2 types with a yaw damper. A C 210 where it hardly made a difference and most of the time was left off, and a V -tail Bonanza where it made a huge difference, so much so that the owners wife insisted it be fixed when it stopped working because the kids in the back seat would throw up anytime there was significant turbulence.

The degree of yaw stability present and the distance the seats are from the yaw axis would determine how much difference a yaw damper would make. My guess, and it is a total SWAG, is that the TB 20 is probable already reasonably stable in the yaw axis and the seats are clustered around the apparent yaw axis so you won't see a big difference with a yaw damper on.

It is not a cheap mod (over 12 K) for the 340 and I think you could find better things to spend your money on.

Wine, Women, and Airplanes = Happy

For a light 4 seater piston, I'd classify a yaw damper in the nice-to-have category, but nothing more.

Having said that, the DA42 comes with a yaw damper, and while its effect is not dramatic, it does actually have a subtle but noticeable effect on ride quality, both in calmer & turbulent conditions. I'd generally leave it on.

Even the crappy S-TEC rate based APs have the option of a yaw damper, although they can't fly an ILS halfway straight in light turbulence.

I don't think it makes any sense for airplanes where all seats are near the yaw axis.

I was thinking of it in terms of improving the stability in turbulence, rather than passenger comfort

The TB is very stable already and the KFC225 handles it really well even in rough weather. But any improvement is worth looking at.

One issue may be that Honeywell do not appear to have ever documented the yaw servo attachment metalwork.

Shoreham EGKA, United Kingdom

I was thinking of it in terms of improving the stability in turbulence, rather than passenger comfort

The two are the same thing.

EGTK Oxford

The Cirrus SR22T I fly has a yaw damper and I use it all the time up to DA on the approach. When I deactivate the AP using the AP knob on the stick, the YD is turned off.

It makes a lot of difference in the climb, but gives more comfort to the pilot at first with not having to use the right rudder that much.

When taking 315 HP in the Cirrus and taking off, you have to use quite a lot of right rudder all the way up. Turning on the AP but without the YD on, you still have to push the right rudder a lot to stay coordinated. The Yaw Damper takes this over.

EDLE, Netherlands

Same in the PA-46 but I just use rudder trim.

EGTK Oxford

The SR22 YD must have a massive authority if it can do the whole rudder trim during takeoff! I wouldn't like to see a failure of the electronics on that. Normally a YD is limited to a few degrees of rudder movement.

Shoreham EGKA, United Kingdom
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