Thinking about a Third Autopilot Servo

[svyolo]

Is am not sure how well it will work to reduce adverse yaw. It should help some. Are there any options to adjust the gains or aggressiveness of the yaw damping function?

[Chris In Milwaukee]

Isn’t a yaw damper there just to prevent tail wag during cruise? Never thought about it as an adverse flaw fixer upper. But I’ve not seriously flown behind an autopilot, either. I did make funny faces once, though.

[svyolo]

That is it's primary function, but yaw is yaw, and adverse yaw should be reduced as well I would think. The inertial reference senses it, but it doesn't know where it came from. Every aircraft design is different, with different yaw characteristics. Hopefully there is some adjustability to the response of the yaw function.

[jaredyates]

Dynon does have adjustability, but the problem is that until they put out documentation about how the system works, it's just guesswork.

[svyolo]

Thanks again google.

http://www.vansairforce.com/community/showthread.php?t=119555

[Bdflies]

John, I'm flying the G3X touch system with the 307 A\P controller. I elected to forgo the 3rd axis (yaw damper), but could easily add it at any time. Your question about adjustability is a good one. The installation manual, for the G3X system is around 860 pages. It's available from the Garmin site. And no, you don't need to read and implement everything on all those pages. There's just a lot of information about every aspect of installation and getting the system ready for flight. I'll admit that it was intimidating at first. I learned to really appreciate the detail and depth of information. The section about autopilot configuration is about 60 pages. Again, you don't HAVE to spend untold hours on the minutiae of the system. You can, however, adjust torque - response speed - and sensitivity of each axis, independently of the others. So, to answer your question, yes, the Garmin system can be tailored to your liking. I'm quite certain that the other manufacturers systems would be similarly adjustable, but that's just a hunch.

Bill

[Peter Girard]

new trim rudder trim.JPG106_0246.JPG

[Peter Girard]

tail skis 106_0256.JPG106_0255.JPG

[Isilverone]

Hi Jared, I installed my Dynon yaw servo in my tail. Its a Capstan system and have it direct and independent to the rudder horn. I just started building so don’t know how it will work but can’t see how it wouldn’t. Shoot me a text if you wanna chat 306-740-8803

[svyolo]

I read on VAF that some RV-10 guys will turn on the yaw axis autopilot function shortly after takeoff, and leave it on until right before landing. Feet on the floor the whole flight. Maybe I don't have to relearn how to fly a light aircraft after all? :<)

[Peter Girard]

new parts

[Peter Girard]

bush tailwheel 12 inch tire

[Peter Girard]

wheelskis for bearhawk

[Chris In Milwaukee]

Are these for sale? Can you (or I) move them to the classified section?

[Mark Moyle]

Neat idea! I'm using a modified Cessna rudder pedal assembly. My rudder cables are in the center like your rudder trim system. I've created a tensioner to keep the cables under tension... your trim system would eliminate and be better than my set up. One suggestion on your rudder trim... raise one pulley on the firewall and cross the chain/springs. That'll cause the nose to move the same direction as the trim wheel rotation.

[rodsmith]

Finishing up the last fuselage details before sandblasting and painting. I've read through this thread a couple times, Decided I'm going to make a provision for a yaw dampener in my G3X system, hopefully I won't need it. Using 4 pulleys I will route 3/32" cable forward then up high enough to clear the brake pedals then across behind the firewall to close the rudder loop. I have just enough room for the pulleys because I mounted my rudder pedals an 1" behind plans location. So all I need to install now is 4 pulley brackets and tabs to mount the servo, which would be the capstan style. Will loop the can bus wiring in that location for a future connection if needed. If I don't end up needing a yaw dampener will make a good start on a rudder trim system.

[BravoGolf]

For just yaw damping due to adverse yaw, wouldn't a strake perform the same function without the complexity? Of course adding a strake after completing the fuselage covering would be difficult. The question is how long and tall would it need to be to reduce the yaw without affecting other flight characteristics.

[rodsmith]

For just yaw damping due to adverse yaw, wouldn't a strake perform the same function without the complexity? Of course adding a strake after completing the fuselage covering would be difficult. The question is how long and tall would it need to be to reduce the yaw without affecting other flight characteristics.

Jared had reported that his autopilot wouldn't adequately turn the plane using roll alone. I have talked to Garmin about the use of the yaw dampener to coordinate turns and was assured that it does that very well. I'm not concerned about yaw oscillations, have never heard that as being a Bearhawk issue. Bill reported that his 2 axis G3X autopilot works well in his Patrol. Mark says you can reduce adverse yaw by adjusting the ailerons a bit above neutral. I will do that and hopefully 2-axis will work well, if not I will easily be able to add the yaw servo.

[Nev]

Interesting thread. If my memory serves correctly a yaw damper is normally associated with sweep wing aircraft to dampen the lateral effects of Dutch roll. Usually in light aircraft this shouldn’t be an issue.

But adverse yaw is very common and (from memory) is caused by the down going aileron causing a higher angle of attack, more drag, and yawing the aircraft away from the direction of turn. This is often compensated very effectively with differential ailerons by reducing the travel of the down going aileron such that the drag is reduced to match that of the upgoing aileron. Some even had a rudder/aileron cross tie (which were next to useless).

I don’t have the practical experience on a Bearhawk. However I would imagine that balancing the controls first might help a lot before needing to add servos.