John Cochrane wrote:
As a rule of thumb, flying 1/2 the MC recommended by the theory/
computer
is a good strategy.

If flying 1/2 the Mc recommended by "theory" is right, that means you
have the wrong theory! Understanding a correct theory is even
better.

Lowering the Mc setting to account for centering time, bottom to top
average rather than best surge of lift, need to stay connected to the
clouds, character of sky ahead, altitude remaining, number of options
left, etc. etc. is all part of good theory.

This does not mean it ever makes sense to cruise at a setting lower
than the weakest lift you would currently take, which is a common
mistake. If you're cruising at Mc 1, but rejecting smooth easy to core
3 knot (bottom to top) thermals while waiting for the 5 knotter, you
would do better by cruising at Mc 2 and taking the occasional 3
knotter, but not going too high in it.

As UH emphasizes, all this is third order. Flying in the right place
and altitude band is the key decision!

John Cochrane
BB

I don't think I made it clear that I was translating into a rule of
thumb for the average pilot (say, me). I've read your paper, and am
convinced, but translating that into my own flying requires a precision
that I just don't have.

So for my purposes I have two options:

Blindly follow the PDA. This would work if I did it, I guess, but
distractions (ooh, shiny!), inattention, picking the wrong route, etc
mean I don't.

Work out a (an?) heuristic which approximates the theory. For me, that's
to take the general reading on my averager during the last thermal
(well. more accurately the next thermal I would accept, but if that part
of the day is consistent the last thermal will do), and then estimate
the relevant MC to fly to the next thermal.

My achieved climb is probably 2/3 of what I see on the averager (UK,
lower cloudbases than many places), so I could choose that as my MC
figure. However, I also know from reading the theory that the difference
in achieved speed over the ground from flying a little faster or slower
is a few percent (2-5).

Thus if I fly half what I saw on the averager, I'm close to (though
below) the optimum speed, but have extended my range. Or, to put it
another way, I'm flying less than 5% slower than someone who can fly to
the theory, but giving myself a larger margin to compensate for the
errors I know I will make.

This is not a strategy for winning contests, but it works quite well for
completing the task. It's also pretty simple in the UK because a day
when I see 6kt consistently on the averager is execptional. Thus I only
need to memorise four speeds to fly (MC 0-3) and remember how to divide
by 2.