A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Soaring
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

AT, TAT, MAT?



 
 
Thread Tools Display Modes
  #41  
Old October 16th 08, 12:22 AM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 193
Default AT, TAT, MAT?

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

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...


Apples and oranges - the (now defunct) 15 minute rule flattened out
the points awarded as a function of time on course OVER AND ABOVE the
minimum time. It was an attempt to reverse out an implicit scoring
penalty due to the dilution of final glide speed into sustained cross-
country speed - longer flights got penalized more as the dilution
effect decreased.

The second topic has to do with flight management - being on time but
not under. The penalty for being under time is much more severe than
the hidden penalty for being over - you get marked to minimum time,
which is like averaging in zero speed for the time you are under.

Hope that makes sense to people.

9B
  #42  
Old October 16th 08, 12:23 AM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 193
Default AT, TAT, MAT?

On Oct 13, 4:25*pm, BB wrote:
I don't understand - if you add 15 minutes, what's to stop people from
trying to come in 14 minutes and 59 seconds sooner? *Doesn't that just
shift the "minimum task time" without affecting the racing (if not,
what's the logic I'm missing)?


--Noel


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


The main argument against this was due to the rate = distance / time
formula being drilled into us in junior high school. Many people hated
the idea that your speed wasn't distance divided by time. Of course at
that time points were proportional to calculated speed.

Since we have now (I suspect) increased distance points to 600 and
thereby compressed scores so speed points are not necessarily pro-rata
to actual speed around the course, it might be acceptable to re-think
a form of this. While it was analytically elegant to think in terms of
the 15 minutes added in calculating speed around the course I think it
might be better to think about it in terms of how points are awarded
and leave the speed calculation alone. I realize that there are
circumstances where a slower raw speed might earn higher points than a
faster raw speed, but my recollection is that the differences are
minor and the only way this would happen is if someone took a much
longer flight than a competitor flying nearly the same speed. Making
the scoring work with the equivalent of 10 minutes added rather than
15 would likely clean up this apparent anomaly. Also, a modest
incentive not to go chase a cloud street into the next state may not
be so bad.

I would add that, while John's logic and math are absolutely correct
there is often enough going on with the weather that overrrides how
much time you do (or should) spend on course that the logic for being
just on time versus a few minutes late gets washed away like good
intentions.

Now that the government is taking John's advice and recapitalizing the
banks rather than buying their bad loans, maybe we should revisit his
soaring advice too.

My soaring season is done, so I may as well re-hash this sort of
thing.

9B
  #43  
Old October 16th 08, 04:41 PM posted to rec.aviation.soaring
BB
external usenet poster
 
Posts: 140
Default AT, TAT, MAT?


Now that the government is taking John's advice and recapitalizing the
banks rather than buying their bad loans, maybe we should revisit his
soaring advice too.


Just to set the record straight, this is a little joke from Andy.
Don't blame me for this mess of a hideous bailout and goverment
takeover of the banking system! (As if anyone ever listened to my
advice in the first place.) Ok, it's not as disastrous as having the
government buy out every bad mortgage in the country, but not by a
whole lot.

John
  #44  
Old October 16th 08, 05:40 PM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 193
Default AT, TAT, MAT?

On Oct 16, 8:41*am, BB wrote:
Now that the government is taking John's advice and recapitalizing the
banks rather than buying their bad loans, maybe we should revisit his
soaring advice too.


Just to set the record straight, this is a little joke from Andy.
Don't blame me for this mess of a hideous bailout and goverment
takeover of the banking system! (As if anyone ever listened to my
advice in the first place.) Ok, it's not as disastrous as having the
government buy out every bad mortgage in the country, but not by a
whole lot.

John


;-)
  #45  
Old October 16th 08, 07:48 PM posted to rec.aviation.soaring
noel.wade
external usenet poster
 
Posts: 681
Default AT, TAT, MAT?

On Oct 16, 9:40*am, wrote:
On Oct 16, 8:41*am, BB wrote:

Now that the government is taking John's advice and recapitalizing the
banks rather than buying their bad loans, maybe we should revisit his
soaring advice too.


Just to set the record straight, this is a little joke from Andy.
Don't blame me for this mess of a hideous bailout and goverment
takeover of the banking system! (As if anyone ever listened to my
advice in the first place.) Ok, it's not as disastrous as having the
government buy out every bad mortgage in the country, but not by a
whole lot.


John


;-)


In a feeble attempt to make this more glider-related:

I'd like to see the bailout architects *actually* have to bail out.
If they survive, we consider letting them stay in office... But I
can't decide if we give them a parachute or not. ;-)

Also, I believe that commercial glider operations need to lobby
congress. Many are failing or have gone into bankruptcy, and they
need the government's help to stay afloat. We keep hearing that
consumer spending is the lynchpin of our economy, and glider rides and
rentals are certainly an excellent avenue for consumers to spend their
money! Furthermore, once launched the glider is a zero-emissions
vehicle - and we are all conscious of environmental impacts and the
cost of energy/fuel these days; so supporting glider operations is
truly an important issue. It is also a wonderful subject for future
government study. Can you imagine how much fuel we could save if we
could develop a glider-based transportation network? To heck with
those noisy and fuel-burning VLJs, why not launch small 3 - 8 person
gliders to 30,000' and then glide to destinations up to 170 miles away
(hey, 200 miles if the towplane climbs at an angle away from the
airport)? That only requires a 30:1 glide-ratio, which is quite
doable with today's technology! All we need is some money from the
government...

--Noel
(who has now used his XCSoar PDA simulator to "fly" a couple of TATs
and understands them much better)

  #46  
Old October 17th 08, 01:30 AM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 193
Default AT, TAT, MAT?

On Oct 13, 6:39*am, Brian wrote:
Just one more comment. The thing that makes the top pilots so good is
the ability to adapt the or even predict the conditions. *They know
when to go fast and the know when not to. They know when they can get
low and when they shouldn't. How they do this is just basic soaring
skills but they somehow do it better than the 2nd place guy. I have
yet heard anyone explain how they do this consistantly. I suspect it
is just years of experience.

How to come in at the back of the pack I am a much better expert at,
but it is the same things that will put you there. Falling out of the
lift band and having to climb back up in the 1 knot thermal after
passing up the 4 knot thermal will lose you a lot of time. And staying
high and stopping often in really strong conditions with a large lift
band will cause you to fall behind as well. As you can see what works
one day may not work the next or even from one hour to the next. The
pilot that can shift gears at the right time and fly both of these
conditions best on the same day will win the day. The pilot that can
adapt on a consistant basis will win the contest.

The math of getting around the couse fast is pretty simple. Fly the
McCready numbers for the conditions and you will do well. You will do
excellent if you can fly the McCready speed for the next thermal
instead of the last one. Of course there is some art to find the
thermals as well.

Brian


I agree with the first point Brian makes but not necessarily the
second. IMHO there are two fundamental and ironclad rules for fast
racing:

1) Don't take weak thermals - by this I mean take only the strongest
20% or so on average.
2) Don't get low.

Brian's first point speaks to the inherent tension between 1) and 2).
Sailplane racing is a game of maximizing probabilities - if you can
understand your odds at any given point in the flight you will fly
faster than if you can't. By odds I mean things like the probability
of finding a top 20% thermal from where you are at any given time.
McCready speeds are a nice way to think about whether you should be
flying faster or slower for the average lift conditions and through
patches of sink, but being off by even 15 knots on cruise speed is
going to make only about a 1.5 minute difference in task time over a
3.5 hour task. By contrast taking a single thermal at 4 knots instead
of 5 knots for 3000 feet costs you the same time. Fussing around for
three turns in zero sink before you core a thermal cost the same time.
I fly 85-knots dry most days, 95 knots if it's smokin' and 75 knots if
I'm in trouble. That's it.

The main skill I see in going fast is knowing when to press on for the
better thermal versus knowing that the one you've got is the best
you're likely to get before you run out of altitude and ideas. Always
feeling the urge to "press on" - and knowing when to resist it - is
the main point.

I remember taking a start one day last year and gliding, gliding,
gliding for something like 45 miles finding nothing great. I passed on
a couple of 3 knot thermals and was getting low enough that I was
about to turn back towards some fields rather than press on. I pushed
into a wind shadow bowl for one last shot at a climb and found an 11-
knotter. Within three turns a 100 seeding point pilot rolled in
beneath me. I found that thermal at the edge of my comfort zone - I
recall he wasn't particularly nervous about his altitude. For both of
us an 11-knot climb for 7,000 feet really helped the old average.

It's all about managing your odds.

9B
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT +1. The time now is 01:02 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.