| 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: |
| Downgrades: |
|
|
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 ! |
