Meet the Antis

In my recent piece about the yaw centre we talked about the three degrees of motion, but only really covered two of them: lateral motion and yaw. We left out the two rotations round the other axis: roll X and pitch Y. Pic A shows the axes and the motions in them and around them. Sitting comfortably? Well you might need to buckle up too: this ride is about to get ever so slightly technical.

We’ll cover roll in a later article, so let’s start with the least known: pitch. For some reason, in the aerospace context we always talk about pitch in general terms, whereas in vehicle dynamics it is a specific referring mostly to the motion the car performs while braking. This can also be called ‘dive’. We call the same motion going the other way while accelerating ‘squat’ because the predominant feeling during braking is the front going down, or diving, and in acceleration the back of the car going down too – squatting, in other words, just like the gym exercise we all should be doing but usually don’t.

And here comes the first tricky bit: intuitive though this distinction is, it’s actually not strictly, physically true as we shall shortly be seeing.