Flick or Snap rolls
Flick rolls (called 'snap rolls' in the USA) are initiated by rapid pitch and yaw control inputs, causing one wing to partially stall whilst the other still flies - leading to instantaneous high acceleration in roll. This abrupt high energy translation makes the manoeuvre hard to study and hence difficult to judge accurately.
At the entry to the flick roll the aircraft MUST -
- Abruptly pitch positive or negative to briefly set the wings at a critical angle and cause an immediate semi-stalled condition.
- Yaw to unbalance the airflow between the wings, and so reduce the critical angle of one wing whilst increasing the other.
- The initial 'nod' and yaw (can be together or made as a quick "one-two") must immediately produce rapid "auto-rotation". "Auto-rotation" means that one wing has a higher angle of incidence than the other, is in a stalled condition and thus causing high drag, whilst the other wing has a lower angle of incidence, is not stalled and is still providing lift. In true auto-rotation NO aileron is be required to initiate and drive the rolling motion - if you see in-flick aileron applied you might believe that the aeroplane is not really flicking.
- Throughout the flick-roll the aeroplane must remain auto-rotating by continued application of the initiating pitch and yaw control inputs. A translation to aileron rolling at any stage before the required angle of rotation has been completed would mean that the flick has ended early - a certain 1 point/5° downgrade.
- At the correct angle of rotation the roll should cease abruptly, and the aircraft should continue along an axis closely parallel to the extended pre-roll axis. This stoppage must primarily be driven by reduction in the pitch angle and removal of the yaw to un-stall the wings and restore balanced flight, so once again any aileron applied to stop the roll is not the appropriate control.
- Check carefully that the last part of the auto-rotation is not turned into an aileron roll to assist accurate end-stop positioning, a commonly adopted ploy that must be penalised.
Flick-rolls happen so rapidly that it is your subjective 'perception' as to whether the two essential components - pitch and yaw - have been successfully applied to cause auto-rotation, and removed at the right moment to stop it. It is not possible to test the presence/absence of these ingredients from a video, so if you believe they were absent you must use the Perception Zero (PZ) rather than the Hard Zero (HZ).
- If the stall is inadequate the aircraft will fly a 'barrelled' roll with both wings providing lift, and considerable sideways translation from the starting axis is likely - this MUST be given a Perception Zero mark (PZ).
- Don't forget also to check that the manoeuvre you see is positive or negative - whichever one the sequence calls for. If it goes the 'wrong way' it must get a Hard Zero (HZ).
- Aircraft characteristics vary a lot in their requirements for flick initiation, and with some modern types the pitch movement can be quite small. For a given change in pitch angle the tail will probably move further than the nose, so look for a tail movement towards the wheels for a positive flick (as in the diagram above of a one-turn positive flick in level erect flight) and away from the wheels for a negative figure.
- However! It is the duty of the pilot to show you a flick-roll that convinces you it has met the above criteria. If you are unconvinced then clearly your perception is that the manoeuvre has failed to meet the required criteria, and you must give a Perception Zero (PZ).
- If you see a 'flick' that in your opinion is not primarily driven by pitch & yaw or where aileron input is an obvious factor in driving the roll, then you should give it a Perception Zero (PZ).
- In every other important aspect the penalty to apply is the usual 1 point per 5° of inaccuracy observed.