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Precise definition of yaw 
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#1
Jul1511, 03:15 PM

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I'm googled "yaw" for the afternoon and there is a detail that I'm not finding. *One* of my understanding of yaw from my readings is that it is the angle between two /vertical/ planes, one containing the velocity of the moving object and the other containing "longitudinal" axis of the moving object i.e. the fronttotail axis of the fuselage of an aircraft.
This is my own cobbled together idea of waht yaw could *possibly* mean. Nowhere is yaw defined exactly in these terms. Instead, yaw is explained in terms of rotation around the vertical axis, where it sometimes seems that vertical axis refers to the "longitudinal" axis, and somtimes it seems to refer the gravity vector. For now, I assumed the latter. Even so, there is the question of precisely how to measure the angle between the velocity vector and the direction in which the moving object is facing. The possibilities that come to mind are: 1. Just measure the angle between the two. 2. Both vectors projected onto a completely horizontal plane 3. Both vectors projected onto a plane containing (1) the velocity vector and (2) the intersection of the horizontal plane with the plane that is perpedicular to the velocity vector. 4. Both vectors projected onto a plane containing (1) the "longitudinal" vector and (2) the intersection of the horizontal plane with the plane that is perpedicular to the "longitudinal" vector. 5. Both vectors are projected onto the plane containing (1) the "longitudinal" axis and (2) the wingtiptowingtip axis. Thanks for any clarification 


#2
Jul1511, 04:23 PM

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How about this link:
http://www.grc.nasa.gov/WWW/K12/airplane/yaw.html It's got pitchers and an illustrative animation. 


#3
Jul1511, 04:40 PM

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I did run across that....it doesn't really say, but it looks like the yaw axis is also perpendicular to the longitudinal access of the plane. This would mean it is completely unrelated to the direction of gravity (which contradicts previous material I've read elsewhere). Is that correct?



#4
Jul1511, 09:39 PM

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Precise definition of yaw
For rigid body motion, there are 6 degrees of freedom: 3 in translation and 3 in rotation.
Imagine a body like an airplane. Let's assume that the xaxis runs along the center of the fuselage. The yaxis would run perpendicular to the xaxis from wing tip to wing tip. The zaxis is perpendicular to the xy plane. The 3 translational degrees of freedom are as follows (direction of motion as indicated): x: Surge y: Sway z: Heave The rotational degrees of freedom (and the axis about which motion takes place) are: x: Roll y: Pitch z: Yaw 


#5
Jul1611, 07:10 AM

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Normally, yes, "yaw" is rotation about a vertical axis. A more general definition is SteamKing's: given an arbitrary set of three mutually perpedicular axes, which we arbitrarily call "x", "y", and "z", think of a ship or airplane aligned along the xaxis with its beam (or wings for an airplane) in the direction of the yaxis. Then "roll" is rotation about the xaxis, "pitch" is rotation about the yaxis, and "yaw" is rotation about the zaxis.



#6
Jul1811, 08:59 AM

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#7
Jul1811, 09:03 AM

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#8
Jul1911, 09:33 AM

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