The first two comments from the stall turn section apply equally here regarding the pull or push to the vertical line, accurate maintenance of the line, and the eventual pull or push at the foot of the figure.
When the aeroplane reaches the top of the vertical line it will stop for an instant, then begin to slide back downwards. The slide should descend straight back at least half the length of the fuselage without any pitch change before the swing-through starts, or a Perception Zero must be given. In the slide there must be no rotation in the rolling or yawing planes, the wings must remain parallel to the horizon and at right angles to the original entry direction.
- The nose must 'fall through' in the correct direction: either wheels DOWN / canopy UP (the falling element in the Aresti diagram will have a full line) or wheels UP / canopy DOWN (drawn with a dotted line in red as shown in the sketch here).
- Pendulum effect, that is when the nose swings one or more times through the vertical after the initial slide and fall through, doesn't matter. Judgement of the vertical down line begins as soon as this pendulum effect has stopped.
- Check the rearwards slide for length and straightness - you'll need a raised finger or pencil to do this accurately. Also look carefully to see that the aeroplane doesn't roll and yaw as the nose falls through, or gauge the amount if it does.
In the diagram on the right
- Radius 'A' and radius 'D' must be constant
- Length 'B' = length 'C'
- Height difference 'E' is not important
The entry and exit radii must be constant just like a Stall Turn, the usual 1 point/5° applies in pitch, roll and yaw for the up line - particularly at the 'stop', in the slide, and for the down-line, and throughout the pendulum period the yaw/roll attitude must be straight or it must be penalised in the same way.
If you consider that a tail slide does not meet the half-fuselage length rearwards slide criterion then you should give a Perception Zero and not a Hard Zero. Line lengths before and after up or down vertical rolls are judged with the usual 1 point downgrade for a visible variation, 2 for a 2:1 variation etc..