"Bruce Greef" wrote in message
...
Am I right that the reasoning behind the high speed low height dash is
that it takes one of the variables out of the risk equation?

You arrive at a point where you have the finish line made with some spare
energy, but not a lot.

In the USA the Sailplane Racing Association , and in Canada, the Candian
Advanced Soaring websites have excellent discussions on the subject
http://sailplane-racing.org/Articles...llustrated.pdf
http://www.sac.ca/cas/techniques/techniques.html

Books by Reichmann, Piggott, Welch & Irving explain the problem fully.

Modern flight computers can give you Total Energy corrected differential
final glide height. This means that at any time, the computer can tell you
how high above your "safety height" you would be when you reach the finish,
if you slowed to best glide speed-MacCready Zero, or in some computers, if
you slow to the set MacCready speed.

So you follow your MacCready directed speed until you see that you have the
field made--no doubt about it--. Either you see the airport at a comfortable
angle below your glidepath, or the computer says you are a good margin above
your safety height (500-1000 ft) that you have set-and you are just a few
miles (4-6) out. From that point you go to "visual" and burn as much height
as you think safe, while your computer tells you if you are gaining or
losing on the differential. If you set, say 500 in, and the differential
goes to zero, it means you can make it up to 500 if you slow down. Of
course--don't trust your life to this!

In general, a pull up from 120 kt to 60 kt recovers about only 450 ft. So
don't plan on a low 50 ft pass at anything less or you won't like what could
happen. If you are just crawling in, or walking at, say 80-90 kt, plan a
rolling finish, but announce it because you will be landing against the flow
of traffic! Better would be a high pattern---in the USA you lose points for
a rolling finish.

At any rate---These few points may make the difference between 1st and 3rd,
or between 21st and 22nd, but who cares? Nobody will remember if you won or
came in third that day, but they will remember a long time if you do
something stupid.

Hartley Falbaum
DG800B "KF" USA
850 points on a really good day!