In the Belgian cast is an oval constant tension cast with a low sidearm backcast and and overhead forward cast. By placing the backcast and forward cast in two different casting planes and joining them with the oval transition, it prevents a tailing loop. For a the fly leg of the line to hook the rod leg of the line, they MUST be in the same casting plane. So the Belgian cast is also a cure for a tailing loop.
However, there is a disadvantage to the Belgian cast. Because it is an OVAL casting motion, it introduces another twist into the line for every oval casting motion
. If you adopt the Belgian cast as your standard cast for everything, you need to allow the fly line to UNTWIST, by letting it drag in the current, With a light fly, the line will untwist, BUT with a heavy fly, it will not.
So be attentive when you use the Belgian cast to monitor your line for twist. Reeling up a twisted fly line and storing it that way is not good for the line. After you take off the fly, let it untwist before putting the line back on the reel.
"The disadvantage of this cast is that it throws a half twist in the line every cast. Half twists add up! So it's best to use this cast sparingly, otherwise you will have to get into the habit of removing the reel from the rod, every 30 casts, or so, in order to spin the twists out."
The Belgian Cast
Here's a video of the Belgian "Wind" Cast