On Feb 28, 9:52*am, akiley wrote:
On Feb 27, 10:15*pm, John Cochrane
wrote:

I wrote a new article on how to use computers to help judge glides.

http://faculty.chicagobooth.edu/john...ocs/safety_gli...

or the first item here

http://faculty.chicagobooth.edu/john...ndex.htm#maccr...

This will probably end up in Soaring sooner or later, but I always get
a lot of help from early readers. If it's not clear or you see
problems etc. let me know. (john dot cochrane at chicagobooth dot
edu0

John Cochrane

Great article. *Makes total sense. *If we are using flight computers
to do the work of calculating arrival based an many factors such as
wind, polar, bugs, ballast and such, It doesn't make sense to me to
use something like L/D when L/D skips the wind and the polar info.
Arrival height takes these factors into account, but it seems MC
covers so many bases. *It's the theory that describes how to maximize
lift/speed to fly, but can also describe reserve energy for safety
glides. *I always think in terms of required MC to make the nearest
airport as I'm just starting to get into cross country soaring.

When I bought SeeYou, It took me a long time to sort out what critical
items (winds, reserve altitude, polar, bugs, ballast) were included in
calculations I saw in the various info boxes. *When I discovered MC
included all of these items, plus the lift and speed to fly theory, it
seemed a no brainier to use required MC as my safety glide. *With my
home airport as the goto, I would start thinking of heading home when
MC dropped below 8 based on conditions and distance from the field.
10 miles out with minimal lift, and MC 4 to target would make me
nervous.

I've only used SeeYou and XCSoar and they are not connected to our
club gliders.. *I think these apps should have a Required MC to target
info box, and an option to replace arrival altitudes on airport tags
with required MC. *Having a separate info box for ReqMC allows for
using the MC manual setting separately.

I hit a sink street last summer. *The airport I was trying make it to
was aligned with the sink street based on the winds aloft. *My options
were to continue in sink toward the airport, or turn away and hope fot
lift. *I had something like MC 10 to make the airport with 800' safety
reserve, so I went direct and just made it. * ... Aaron