Question

Describe in your own words, the term “Dutch Roll”. Discuss how the Dutch roll mode characteristics depend on the static directional stability and lateral stability.

Answer 1

Dutch roll is commonly observed in aeroplanes. The dutch roll motion can be related with the man skating over the ice rink.

If we know what is mean by rolling and yawing, then it is easier to understand the dutch roll.

Dutch roll is the result of 'Dihedral effect'.

Dihedral effect: In aeroplane, when more air passes over the one of the wing, then that wing produces extra lift. While other wing produces less lift. This is known as Dihedral effect.

Because of dihedral effect, the plane starts rolling. As the wing producig extra lift, it also produces extra drag. So the nose of the plane is pulled towards the side which is creating extra lift.

Static directional stability: Suppose, if the plane turns towards right then the lift vector also tilts towards right. Due to this, the plane experiences slideslip motion. As the nose is towards right, the right wing produces extra lift and hence extra drag. This drag force levels the plane back to the normal position.