Major Errors (1/2)
The rules on the three sorts of zero marks are as follows
Ten or more downgrades simply leads to a mark of ZERO (0.0)
In this case the pilot flies the expected Aresti figure but the judge sees total of 10 or more downgrades, and consequently all marks for the figure are lost. In other words there are so many errors that the judge simply runs out of marks. This is a plain 'zero' and is written on the Form-A as 0.0 - but not "ZERO"! A 0.0 is as valid a mark as 8.5 or 3.5.
Errors of demonstrable fact are marked Hard Zero (HZ)
Here the figure flown is the wrong one (in other words, not as drawn on the Form B/C). A figure might have been flown very smoothly, but if it is not the required figure then the score is Hard Zero (HZ). This includes flying the 'right figure' in the wrong direction, on the A or B axis. If video replay is available you will be able to see and prove that a factual error (a HZ) was made ... or not.
Errors of subjective perception are marked Perception Zero (PZ)
If a pilot flies the right figure but a judge perceives that what he has seen does not meet a required perception criterion, then a PZ should be given. Perception zeros apply to flick (snap) rolls, spins, tail-slides, and for gliders also to stalls in loops and turns. In each case the criterion that must be satisfied will be a fleeting 'judgement' or perception rather than a clearly judgeable error, and the video can not subsequently be used to prove or disprove it.
For judges the 'Perception Zero' has another key quality: if a PZ fails to pass the FairPlay confidence test when the scoring software is run - usually when a majority of the other judges award that figure a non-zero mark instead - it is simply replaced by a more appropriate or 'fitted' value, and this substitution means that a PZ that fails to be upheld does not affect the judges' RI (Ranking Index). Judges are thus free to express their 'perception opinions' without fear that this may affect their standings in the international judge ranking systems.
When would a 0.0 or a PZ be changed to a Hard Zero?
Consider zeros that arise from many downgrades: when using the 1 mark per 5° deduction, if any single angular error exceeds 45° then the mark must be 0.0. However if a single angular error exceeds 90° then the mark must be a Hard Zero; in most cases when an error of more than 90° occurs the figure actually flown will be a different but valid Aresti figure, and it should be marked as a Hard Zero for that reason. There will still be cases where there is disagreement between judges as to whether a full 90° error occurred or whether it was the correct figure badly flown or an incorrect figure. In this situation the Chief Judge will decide which type of zero will apply - although it will make no difference to the Pilots score.
There are some figures where a single error of 45° results is a different valid Aresti figure being flown. For example, a pull to the vertical and fly off when a pull to only 45° is required. It is recommended that, if no attempt at correction is made, then this is marked Hard Zero (ie. it is the wrong figure). If the pilot makes a correction back towards the correct attitude then it becomes a 0.0 - all marks are lost. Aircraft ‘body language’ can help – a firm pull to the vertical, a hold in the vertical with no attempt at correction and a properly executed fly off is simply the wrong figure. A poor initial push followed by a sharp push, as the pilot realises he hasn’t put enough into it, which goes all the way to the vertical followed by the nose wandering back by 20 odd degrees is a case of a very poor attempt at the correct figure.