Methods for judging loops:
Loops are among the simplest shapes in aerobatics, but
unless you have an easy-to-apply method they can be quite
difficult to judge and consequently decide on the correct downgrades to apply.
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Look at the Basic
Loop diagram on the left.
Note that: |
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The exit
point is
at the same level as the entry point. |
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The four quadrant
radii and centre points are all the same. |
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The centre-top
point is
exactly above the start point.
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Wherever you see
these 3 'truths' you can be sure that the loop is genuinely round. |
So: For every loop, in your
mind break the shape into the four 90° quadrants for
easier comparison. |
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Put a pencil or pen up
against the start point, and use this point and the 1st
quarter loop as your reference. Now you can describe the
remaining quarters, particularly their radii and end
points, by comparing them with the first quadrant and the
location of the original start point. Note also the
angle that each quadrant describes about the centre of
the first arc - this should always be 90°. If it's well
flown and the shape really looks
like the one above, then it's probably worth a ten. |
Here are some classic errors in the
sketches on the right: |
1 |
The 1st half
is fine, then the radius gets smaller at the top. The 2nd
half is tighter, and the exit significantly higher than the entry. |
2 |
The 1st half again
is fine but the top is flattened with increased radius.
The 2nd half
is larger than the first, and the exit is significantly lower than the entry. |
3 |
This one has a definite
"Lazy Sunday afternoon" style - possibly with the same stick
position until the end.... then a big pull. The 1st half radius tightens
towards the top as
the aeroplane floats at below stall speed inverted, then in the 2nd half
it falls freely until increasing airspeed gives the elevator
some bite and 'down-rush' anxiety tightens the radius again
to a low exit. Not good! |
4 |
In this half-loop
the 2nd quadrant radius is tighter than the 1st, leading to a smaller 2nd
half and early exit not over the entry point. |
5 |
Here is the
opposite fault, where the 2nd quadrant has been forced
to a larger radius to 'float' the top and avoid (4) -
making the exit too high and once again not above
the entry point. |
6 |
In eights it is
also necessary to judge the relative size of both the
looping elements. Use the pencil to 'fix' the start as usual, then
with a finger or by reference to some local cloud
feature make a judgement about the size of the 2nd loop and the
exit trajectory. |
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Downgrades:
As you watch the figure, for every radius variation, missed
angle point, entry and exit height mis-match you see, simply
accumulate the penalties below and subtract them from 10 to
reach the final figure score: |
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Arc radii |
A small but noticeable variation: -1 point |
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A more significant but not serious variation: -2 points |
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A large variation significantly changing the figure shape: -3 to -4 points |
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Missed angle |
Where the 'top point' is < or > 180° from the bottom point:
-1 point per 5° |
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Height mis-match |
A small but noticeable error: -1 point |
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A more significant but not major error: -2 points |
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A large error that significantly changes the figure shape:
-3 to -4 points |
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