Inter-thermal cruise speeds?

On Feb 7, 5:00 pm, Mike the Strike wrote:
Frank:

One thing that classic MacCready theory doesn't take into account is
the depth of the working height band.

It would be a foolish pilot who set his computer/ring to MacCready 5
on a day with 5 knot thermals that topped out at 1,500 feet AGL, but
with cloudbases at 15,000 feet you could probably set it at 6 or
higher. Several pilots I know set their ring almost as a function of
height rather than thermal strength.

The chance of you hooking up with a good thermal increases with the
top of the lift and you can increase your speed accordingly. When you
get low, you need to slow down. There have been some good articles on
this if you search the databases.

Mike


Mike,

Working the bands is very common and I think of it as setting the MC
to the strength of the next thermal "I am willing to take". The day
average may be 6 knots, but if I am low and willing to accept a 3 knot
thermal I will set the MC to that. As I get lower the odds of finding
a good thermal are reduced and I am willing to take a weaker thermal
to get back up in the band or at least get the range to hopefully
reach a better thermal.

In the Western US there are many summer days where dropping below the
mountain height can cost you dearly in time to get back up. In the
14-18 K range I tend to fly MC+5, 12-14K MC for the average thermal
strength I am expecting still to find, 10-12 K I dial back to extend
range, 8 to 10K back further and below 8 back to zero. This is with
base elevation about 5,000 in the valleys.