Judging the "not so good" rolling circles
Rolling circles or turns are one of the most complex figures in the catalogue to judge, and they also happen to be pretty difficult to fly accurately. Throughout the figure, which can last as long as 20 seconds, you must look out for and cumulate errors that arise from:
- Variations in the angular rate of roll.
- Variations in the angular rate of the turn.
- Variations on the altitude of the flight path.
- The wings-level accuracy of any mid-figure changes in the direction of roll.
- The angle of roll at the beginning and especially the end of the figure, where a good deal of yaw angle and 'skidding' of the aeroplane is also likely.
The problem for pilots is that what the rules demand is in reality extremely difficult to achieve. Maintaining the same rate of roll and turn and flying at a fixed altitude while the wings are within 20-30° of level is a very demanding task, as many aeroplanes lack the rudder authority to produce the co-ordinated yaw and turn necessary. A solution often seen is for the pilot to apply extra 'pull' or 'push' during the wings-vertical sectors to co-ordinate the whole picture at the 45° and 90° points, causing two variations in the rate of turn during every half-roll as the aeroplane first trails and then leads the smooth turn that is required.
The problem for judges is that the sheer size and overall timescale of the figure combined with the relatively slow rate of simultaneous roll and turn and height variation make it very difficult to isolate and identify the subtle changes that almost inevitably occur. Applying the fixed downgrades demanded by the rules is much harder than with the more snappy figures, the tendency being to to err on the safe side and be 'kind' to the pilot. In judging however you must always compare what you actually see against the precise standard required, recognise the errors and subtract the appropriate downgrades; rolling circles are not an exception!
In reality therefore
Often you will see something like the sketch above rather than the idealised diagram on the previous page. There will be periods of rolling but with a very low rate of turn while the roll angle is within 20-30° of wings level, interspersed with periods of much higher turn rate as the wings pass through the vertical position where the pilot can use 'pull' and 'push' to bring the total amount of turn up to match the roll. Hold your pencil up in line with the axis of the fuselage to monitor the true rate of turn throughout the figure, and you will clearly see the turn rate rise and fall. The aeroplane may also 'porpoise' up and down, depending on whether the outer wing is above or below the horizon, leading to significant changes in altitude. In the case shown above, assuming that there is a constant roll rate but obvious discrepancies in the rate of turn due to clear evidence of excessive 'pulling' and 'pushing' and also some minor height variation:
- Change in the rate of turn (four times @ 1 point each), 4.0
- Variation in height of 100ft (not shown above, but ...), 1.0
- Exit flight-path angled about 10° away from the intended axis, 2.0
- Final mark: 5.0
In practice, to receive a mark greater than 7.5, a rolling turn must be flown to a very high standard!