"Richard Hertz" wrote:

It isn't the glide ratio that one is concerned with in thermals - rather the
minimum sink rate and the speed for minimum sink.

You've got too much glider time :-) In a glider, you want
to thermal near min sink speed. In an airplane, you want
max excess power, and that's Vy, max rate of climb.
However, at Vy in most aircraft, your turn radius will be
quite a bit larger than most thermals, so you end up trading
off turn radius for climb rate if you're going to turn in
thermals. You'd probably only want to do that if you're
trying to get over a mountain pass. As others have posted,
most of the time you just want to use the free energy that
thermals give and to do that, you slow way down and spend
time in rising air, dive through sinking air and fly the
cloud streets.


Usually thermals are fairly localized and glider pilots work a lot to stay
in them. Turns are routinely done by banking between 30 and 60 degrees at
slow relatively slow speeds.

To do this right you need to find your minimum sink speed. Take some glider
lessons and you may get good enough to make it worth worrying about, but I
doubt you can make it work well in a power plane.

If on the other hand you can find some nice ridge lift or wave, then you can
save some gas.

The varios on gliders are generally quite sensitive and finding a thermal in
a power plane is not going to be trivial. Especially if you want to go
someplace.

My advice is to forget about it, but if you are curious, take up soaring -
it is a lot of fun and will improve your piloting skills and knowledge.

It's an effective technique for increasing cruise speed,
reducing gas usage and for climbing to cross high terrain.
Todd Pattist
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