[quarkz]

Hi,

I'm trying to simulate 2 cases:

1. an aircraft with 1dof in pitch.
2. an aircraft with 2dof in pitch and vertical translation.

In case 1, the aircraft pitches up and remains constant after a while. Pitch moment is approximately zero.

In case 2, aircraft pitches up and then down. Similarly, the angular velocity (vel)changes from positive to negative, which explains the aircraft pitching up and then down.

Pitch moment increases from zero to a maximum before decreasing again. However, it is always positive. But how is it possible that the aircraft pitches down after a while. As moment is positive, the angular acceleration (acc) will always be positive since:

Moment = I*acc

If acc is always positive, how can the vel change from positive to negative?

Is there anyone who knows the reason?

Thanks.

[quarkz]

I managed to solve the problem. It is due to the reference frame of the moment calculation. It is explained here:

Confusion abt cm & CofR position in 6dof and non-6dof scenarios