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Yaw String

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  • Yaw String

    A friend of mine who has built several airplanes and has a Pipistrel motor glider suggested early on that I tape a yaw string to the windshield of my LSA for the flight test period. I have used them on gliders, but thought that the prop wash would cause inaccuracy. I tried it anyway and found that I was wrong. The yaw string works great, just as it does on gliders. In fact, the yaw string told me that the skid ball on my MGL EFIS was giving me slightly bad info, so I experimented and found that I needed to "educate" the MGL by telling it when the airplane was straight and level in the air. The yaw string made this easy and also demonstrated the amount of lag in the skid indicator in the MGL.

    I first taped the yaw string to the base of the windshield, but that did not work well; too much turbulence. I moved the tape point on the windshield to just above my line of sight to the horizon, and shortened the string to about 6 inches, and that has worked well.

    I think the yaw string is better than even an old fashioned liquid filled skid ball because it works instantaneously and because the string has almost no mass, it is always accurate, even in rough air. Try it; I think you will like it. Bob

  • #2
    I curious if you could get a very accurate indication of your angle of attack with a piece of yarn taped to the side window. Or maybe edge of the window as it curls around the before it terminates at the door post?
    Brooks Cone
    Southeast Michigan
    Patrol #303, Kit build


    • #3
      For my flight two days ago, I taped strings to the bottom of my left strut about half way out, and also to the left window. When I did full turn spins to the right, the string on the strut was about straight back, the string on the left window was also about straight back. The yaw string initially went to the left, as I thought it would, but it then moved back to the center as the spin went nose down and started to wind up. That I did not expect, but I would bet that this would vary somewhat for different airplanes depending somewhat on where the center of rotation is relative to where the yaw string is mounted. It also might change as the spin develops more and the tail comes down some relative to the horizon. When I spun to the left, both the strut string and the window string were back, but were fluttering lazily. I also checked the skid ball. It behave as expected when I applied the rudder to start the spin, but it then came back pretty much to center. I was surprised at that, also.

      I checked both the window and strut strings in climb and descent, and they stayed so close to straight back as to not be useful, at all, so I removed them.

      I plan to lower my windshield yaw string so that the string itself is right in my line of sight and the tape is below my line of sight. That would be better as I would not have to look up to see the thing. I'm hopeful that I can do that without getting the string back into turbulent air.