AT, TAT, MAT?

On Oct 13, 9:39*am, Brian wrote:

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,

One 'dirty little secret' is that the fast guys aren't using MacCready
speed to fly. Instrument lag, aerodynamic losses, inertia, hazard to
other traffic and loss of attention better placed elsewhere to name a
few reasons that it is found not to work very well.

In weak to moderate wx, the speed to fly vario is set to Mc = 2 and
the cruise audio deadband is set wide (20 kts) to keep it quiet unless
you barge into big sink or big lift. Cruise speeds are chosen
according to "confidence" (see BB's articles) and they are in the same
range as the MacCready speeds, but no effort is made to "optimize"
speeds based on lift/sink of short duration. You do see guys pulling
up to bump thermals, etc, usually higher in the band where the lift is
apt to be broad. Dry 15m/std class ship, weak/mod wx, confident = 80
kts, need to stretch glide = 65 kts, survival = 55 kts. Attention is
directed out of the cockpit. The truth is out there.

-T8

On Oct 13, 7:22*am, wrote:
On Oct 13, 9:39*am, Brian wrote:

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,

One 'dirty little secret' is that the fast guys aren't using MacCready
speed to fly. *Instrument lag, aerodynamic losses, inertia, hazard to
other traffic and loss of attention better placed elsewhere to name a
few reasons that it is found not to work very well.

In weak to moderate wx, the speed to fly vario is set to Mc = 2 and
the cruise audio deadband is set wide (20 kts) to keep it quiet unless
you barge into big sink or big lift. *Cruise speeds are chosen
according to "confidence" (see BB's articles) and they are in the same
range as the MacCready speeds, but no effort is made to "optimize"
speeds based on lift/sink of short duration. You do see guys pulling
up to bump thermals, etc, usually higher in the band where the lift is
apt to be broad. *Dry 15m/std class ship, weak/mod wx, confident = 80
kts, need to stretch glide = 65 kts, survival = 55 kts. *Attention is
directed out of the cockpit. *The truth is out there.

-T8

There's a lot of good info here, both about generalized racing
strategy and specific strategies for TAT and MAT tasks.

A couple of items for thought:

I definitely observe multiple styles of racing. I have archetype
pilots in mind for each style, but won't mention them here except to
say that they all are frequently at the top of the scoresheet. One
style is the "McCready purist". This style involves flying fast and
straight between thermals and only stopping for the strongest lift.
More often than not this style uses a bigger chunk of the altitude
band that other styles. Some portion of the time this style will get
you in trouble that you will have to dig out of (or land out) and some
other portion of the time you will smoke the field. All it all it it a
higher variance strategy. A second style is the "stay up in the lift
band" style. This style is generally marked by below-McCready cruise
speeds. You can justify this on several grounds, depending on the
conditions. If there are clouds, staying in closer contact helps you
find more and stronger thermals. Staying higher has a True Air Speed
benefit. Staying higher by flying slower gives you more search
distance to find that exceptional thermal. The third style is the "go
for the lift" style. This style looks a lot like the second style,
except that there will be a lot more course deviation - zig-zagging
cloud to cloud, following a line of convergence or a terrain feature
off course line or meandering about in an area of lift to find the
hidden boomer. There are overlays to these styles in terms of cruise
speed versus altitude and how to manage upwind/downwind turnpoints,
for instance, that have been discussed elsewhere and can be applied
irrespective of overall style. I have migrated my style from
something more like the first to something more like the second or
third over the past few years. It has made a big difference.

One way see how efficiently you are flying is to look at a metric like
percent of time spent circling in a program like SeeYou. A good
flight in the west for me will have that percentage in the mid- to
upper-teens with an average L/D of better than the ship's best L/D and
a task speed in the mid-eighties or above - this is without ballast.
If you do the math, this is far better than theoretical McCready
theory would predict. This of course means by definition that to win a
competition task you have to find ways to exceed the predicted
theoretical performance of your ship. That usually involves climbing
without circling whenever you can - remember when you circle you are
going backwards half the time.

With respect to AAT and MAT. People have correctly identified a key
consideration as NOT being under time. This is hardest to do on an AAT
where the last turnpoint is a long way from home. This past summer I
made a turn for home 100 miles out and ended up 25 minutes over time
because the outound leg had been much stronger than the homeward one.
Since you don't really know the weather in all the turn areas you have
to start out with an estimate of where you MIGHT go based on the
forecast (deeper into the stronger turn areas or where there will be
more clouds, markers on course, etc.). Then you have to think of the
major scenarios and try to keep you options open. I generally take off
with a cheat sheet on required distance versus task speed in the
allotted time and at least SOME idea of what each leg might look like
if I am averaging 75-95 mph on course. My approach is to keep going
into the early cylinders if the conditions are good. If the later
cylinders are even better you can think about going over time. Keep at
least a 10 minute "over" buffer on arrival time - more if the last leg
is long. Another thing to keep in mind is to try to avoid making
dogleg courselines - you don't get any credit for the extra distance.

On MAT - have a good chart with all the turnpoints and terrain on it
so you can see everything clearly at once (Glide Plan is a good tool
for this. I scale my charts a 25%). Trying to pick turnpoints off the
flight computer is to hard to do well. Generally, I try to fly
relatively longer legs - particularly early on. You will often find
MATs used when the whether is less predictible - keep this in mind in
terms of not getting cut off from home. If you can find the part of
the task area that is really cooking then try to set up a zig-zag
pattern that keeps you there without the dreaded repeated turnpoint
penalty. These are the days where the right move can really move you
up the scoresheet because the fleet is frequently scattered all over
the task area with varied conditions.

9B

What skills do we need to fly a MAT or TAT? As you know it's a wormy
little problem involving several variables; time, distance, altitude
required, wind, speed-to-fly and where's the stinking lift?
..... Practice,
Practice, Practice, and get the best airborne computer available, not
cheap but worth every penny.
JJ


I hate to even think of mentioning it, but adding 15 minuites to
everybody's time makes this whole business of trying to nail the
finish time much less important.
Flame suit on -- no, don't worry, I don't imagine it will ever come
back

John Cochrane

On Oct 13, 1:58*pm, BB wrote:
What skills do we need to fly a MAT or TAT? As you know it's a wormy
little problem involving several variables; time, distance, altitude
required, wind, speed-to-fly and where's the stinking lift?
.... Practice,
Practice, Practice, and get the best airborne computer available, not
cheap but worth every penny.
JJ

I hate to even think of mentioning it, but adding 15 minuites to
everybody's time makes this whole business of trying to nail the
finish time much less important.
Flame suit on -- no, don't worry, *I don't imagine it will ever come
back

John Cochrane

I'm right behind you John - about 50 feet behind. ;-)

9B

The good stuff keeps pouring in... And its very much appreciated! I
also happen to know that there are a few other contest-newbies lurking
on this thread, and hopefully learning as well. :-)

On Oct 13, 1:22*pm, wrote:
is long. Another thing to keep in mind is to try to avoid making
dogleg courselines - you don't get any credit for the extra distance.

Quick clarification on this:

I hear people talk about "going deeper into the circles" - but there's
nothing special about staying inside the cylinder if you appear to be
below minimum time, right? For example: say there's a cloud-street
just outside the first turnpoint cylinder that runs at an angle to
your second turnpoint course-line. Rather than going deep into the
first cylinder (past the center mark) and then making a shorter leg to
the next waypoint, couldn't you run into the cylinder as far as the
lift is strong, then turn back and hit the cloud-street and keep your
ground-speed up... Oh, wait...

Hehehe, just realized my mistake in the middle of this train of
thought: The scoring isn't based on the average airspeed/ground-speed
of the glider, with penalties if you miss the TPs or come in under-
time... Your speed is based on the most advantageous fix recorded
inside each cylinder, isn't it? :-P

--Noel
(Now secretly hoping for a simple AT in his first contest flight) :-)

On Oct 13, 1:58*pm, BB wrote:

I hate to even think of mentioning it, but adding 15 minuites to
everybody's time makes this whole business of trying to nail the

John Cochrane

John -

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

Bravo Bravo's giving you his little secret on how to never end up
early.......start home when your computer tells you your 15 minutes
over time and you should never get there early. Usually works, but I
once turned 15 minutes late on a day where I had been flying with M/C
of 2.5 (remember time-to-go changes with M/C setting) Well I started a
100 mile final glideinto what developed into cloud street and I ended
up 10 minutes early. lesson learned, set M/C for expected conditions
on final leg which should have been 4 in the above example.
JJ



noel.wade wrote:
On Oct 13, 1:58�pm, BB wrote:

I hate to even think of mentioning it, but adding 15 minuites to
everybody's time makes this whole business of trying to nail the

John Cochrane

John -

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 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

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

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 -