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