PPRuNe Forums - View Single Post - Slip vs Spiral Instablilty
View Single Post
Old 22nd November 2006 | 07:36
  #11 (permalink)  
foxmoth
25 Anniversary
 
Joined: Dec 1999
Posts: 3,077
Likes: 1
From: Oop North, UK
That is basically correct. Dutch roll can be gone into in great depth.
This is quite good for a basic description.
http://en.wikipedia.org/wiki/Dutch_roll
note particularly the following :-
Dutch roll results from relatively weaker positive Directional Stability as opposed to positive Lateral Stability. When aircraft rolls around the longitudinal axis, a sideslip is introduced into the relative wind in the direction of the rolling motion. Strong Lateral Stability begins to restore the aircraft to level flight. At the same time, somewhat weaker Directional Stability attempts to correct the sideslip by aligning the aircraft with the perceived relative wind. Since Directional Stability is weaker than Lateral Stability for the particular aircraft, the restoring yaw motion lags significantly behind the restoring roll motion. As such, the aircraft passes through level flight as the yawing motion is continuing in the direction of the original roll. At that point, the sideslip is introduced in the opposite direction and the process is reversed.
which is pretty much what you were saying but in more depth.
This is not often a feature in light aircraft.

n.b. I would completely ignore the article at the end, about the manouver, apart from where it says "This coordination technique is better referred to as "rolling on a heading",", this is not what most people mean by Dutch Roll.

Last edited by foxmoth; 22nd November 2006 at 08:28.
foxmoth is offline  
Reply