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

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) :-)