Hi Mark
A control point in simply an additional turnpoint
(as opposed to a remote finish) placed next to the
airport so as to bring gliders round to finish from
a direction where an appropriate finish gate can be
provided. As per UK rules this is the usual 1/2 km
radius circle and 20k (I think) thistle. If you aren't
sure about the thistle part (I don't know if it has
an equivalent in US rules) there is a diagram on page
11 of:
http://www.gliding.co.uk/forms/competitionrules2005.pdf


For an example of Control Point use look at this
task from last years junior nationals:

http://www.lasham.org.uk/comps/natio...p?comp=b&ddate
=Saturday%2021st%20August

Lasham has a very open finish line coming in from the
west but no suitable place to locate a finish line
from the north, so each day where the task came in
from the north an aditional turn point (in this case
TP4) was added to force competitors to approach from
the west.
A glider has not finished until it has crossed
an on airfield finish line or entered the finish circle
(page 12 of the above pdf).

You mentioned the self selection of turnpoints
in the US Sports class (I assume that is similar to
our Club Class). In this case might it not be an idea
to have the provision for a mandatory turn point at
the end of the task and say 'you may select the order
of your turnpoints but your final turnpoint must be
this one'. This would seem to eliminate the whole
problem of converging gliders at low level without
necessitating the use of such a large finish cylinder
(which I have to admit I am sceptical of the value
of). There are obvious issues regarding the use of
thistles and penalty sectorsif the direction you are
approaching the airport is not fixed (in UK competitions,
the order of turns is usually fixed), but I think these
could be alleviated by the use of a simple 1k cylinder.
The idea of the thistle I believe is to allow a pilot
to round a turnpoint further out if the conditions
at the turnpoint are unfavorable, but as the control
point is very near the finish a pilot would be trying
to get to that exact location so the thistle could
be discarded at this point, leaving a 1 or 2 km radius
cylinder as the only point.

Cheers

Jamie

p.s. I have to admit that on that day during the Juniors
I forgot about the conrol point and went straight for
the finish, recording a gps landout a few k from the
airfield, d'oh!



At 18:30 11 March 2005, Mark James Boyd wrote:
Jamie,

That is exactly what I was thinking. A control point.
Yes, sort of like what we locally call an IP (initial
point)
when entering on the 45 for our normal pattern to land.

We are fortunate to have a huge metal tank maybe
50 meters
diameter that could be used as this remote 'control
point' and
is in line with the 45 entry (sort of). It is probably
3-4 km
away. At 500ft AGL in a 2-33 with a headwind this
would be a little
close, but in the L-13 or anything sexier it looks
ok.

Thanks for your post! Control point. I like that.
Is it scored as an OZ or a cylinder? Scoring as an
OZ
would take a little bit of thought, and as a cylinder,
I'd
expect it'd need to be pretty narrow to not cover the
airport.

In article ,
John Doe wrote:
Mark,

I think what you are getting at is what we in the UK
call a control point, a final turnpoint that must be
rounded in the normal way, but is only maybe 5-10 km
from the airfield, each glider is a few hundred feet
(or more depending on the pilots saftey margins) up
at this point and after turning the control point,
competitors turn to the airfield and dive to a known
linear finish gate. There is generally no minimun
finish height so often the gate is crossed under 50
ft but as all competitors are coming in from a fixed
direction towards a small and clear area of land it
eliminates the vast majority of head to head at low
altitude issues and I've never seen congestion at a
control point myself (altough as my own competition
experience is rather limited I won't say it never happens).

As for non comp gliders, everywhere I've been competing
the daily briefing for non-comp pilots always stressed
the comps procedures as well as use of the radio to
ensure separation in launch, landing and finishing.
As long as the finish gate is suitably chosen to be
away from the main landing area and obstacles with
space to land after as well as an easy entry into circuit
for those with the speed to do so it can be both a
safe and an exciting way to finish without the artificial
complications of raised finish lines.

John,

Whilst some of those accidents are attributable
to finish gates, I'd certainly question your thinking
the last three.
Taking the Discus crash for example, in a Discus
(in which I have a reasonable if not spectacular amount
of time), 500' is adequate, if not totally comfortable,
for a decent enough circuit, that crash, as well as
the others, from the reports seem to be the whole 'slightly
low in the circuit leads to a poor turn leading to
a spin in' issue.
Where the blame in that lies is the topic for another
thread but that, like the other last three, does not
seem to be attributable directly to finish gate issues
as surely a pilot just making it over a 500' 1 mile
finish gate would be in exactly the same situation
as someone who has just got a few hundred feet of height
from a competition pullup?

The others seem to be 'insufficient speed, insufficient
time to recover from the spin', afaiks the same situation
as trying to scrabble over a start gate at 450' and
screwing up.

It's been said before but unfortunately you can't legislate
good judgement.

Cheers

Jamie Denton

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Mark J. Boyd