Hyde244 said:
And so you have noticed the difference between a barrel roll and inline roll. Two different inversions, with barrel rolls rotating around the riders while inline rolls rotate around the track.
I'm almost sure every roll on modern coasters is heartlined, and true ''inline'' roll does not exist.
If you compare a B&M wing coaster train to Furius baco, Arrow 4D or even B&M dive machine,
B&M wing coaster is unique that its wings extend downwards (to the track),
so the heartline is closer to the track, but still not completely co-planar with the track.
It still has a heartline of ~0.5m instead of zero (which would be the only case where an inline roll is the same as a heartline roll),
compared to 1m+ of the other winged train styles.
The reason why B&M wing coasters' rolls look like a straight line is just its hearline is low enough that the track warping is invisible to the bare eye from most angles. From the photos on page 65 you can still see that the rolls are heartlined.
It has nothing to do with whether the roll is zero-g (parabolic) or plain barrel roll (straight),
and also, apparently you can't have 2 different heartline heights for the same coaster.
Even on 4d coasters, the axis of seat rotation is on the heartline.