AT, TAT, MAT?

On Oct 13, 4:41*pm, "noel.wade" wrote:
On Oct 13, 4:25*pm, BB wrote:





I'm guilty of being too obscure. A few years ago the US experimented
with the following rule. To determine your speed for scoring, we take
(Time + 15 minutes)/distance. Time still had to be greater than
minimum time.

The effect of this change is to offset the fact that you get one fast
final glide, or equivalently one fee thermal to the top of the start
gate, per flight, and therefore remove the critical importance of
finishing close to the minimum time.

For example, suppose you fly 50 mph through the air -- top of start
gate to top of last thermal -- *and then *do a 15 minute, 100 mph
final glide on a 2:00 hour turn area task. If you fly it perfectly and
finish in two hours, you go (50 x 1.75 + *100 x 0.25 )/2 = 56.2 mph..
If you blow it and do a 2:30 flight, you go (50 x 1.25 + 100 x 0.25) /
2.5 = 55 mph * or 972 points. That is a huge difference in contest
soaring, so no wonder pilots invest in thousands of dollars of
computers.

*If you add 15 minutes to each time, though, you get scored for 50 mph
in each case! The 15 minute time addition exactly offsets the one-
glide-per-flight effect and makes it unimportant how long you stay
out, so long as you end above minium time and fly fast.

I wish I could say that this was overturned by the evil conspiracy of
flight computer manufacturers. Pilot confusion and poor salesmanship
by its advocates *did in a very pretty idea.

And I am not trying to revive it -- lost cause!

John Cochrane

OK, got it. *Not sure it works in all cases (though it worked OK in a
few random-number cases I threw at it), but I understand it now. *My
newbie brain works better when this is phrased "add 15 minutes at 0mph
on to the end of your flight" (this also jives with your "free
thermal" explanation, since if there's no wind your speed along the
course is effectively zero when you're thermalling straight up).
*shrug* Maybe I'm just weird.

I still don't see how this changes the problem with people coming in
under-time, if the raw time (before adding 15 minutes) still has to be
greater than the minimum task time...

BTW there's a little typo in your example numbers. *The longer-flight
pilot spent 2.25 hours at 50mph, not 1.25. *:-)

--Noel- Hide quoted text -

- Show quoted text -