A man who has one vario knows exactly the airmass movement rate.Â* A man
who has two is never quite sure.

This discussion sounds like the military way:Â* measure with a
micrometer, mark with a grease pencil, cut with an ax.Â* Do you really
believe the current altitude record is accurate to 5 significant
digits?Â* Is that in meters or in feet?Â* I know they claim centimeter
accuracy with GPS, but is it repeatable?Â* How about the thickness of the
line on a barograph, a kink in a pneumatic tube or a spot of sunshine on
the tube?

We went into space mostly with three significant digit accuracy (think
slide rules), why is a glide ratio so important when it's such a
transient thing in an active airmass?Â* I have witnessed a 25:1 glider
(or less) beat a whole gang of 40+:1 gliders.Â* It's the pilot, in the
glider, at that moment, and at that location that makes the performance,
not a number on a graph.

Just my two cents worth.

Dan

On 9/18/2017 9:06 PM, Eric Greenwell wrote:
Dan Marotta wrote on 9/18/2017 10:01 AM:
Your vario sink rate is an indicated rate, as is the airspeed
indicator, so your
calculated glide ratio, /_in the airmass_/ should be a simple
calculation.Â* Having
said that, the air is too dynamic to care what your instantaneous
glide ratio is
and, like thermals, and investments, past performance is no guarantee
of future
performance.Â* It's all "golly, gee-whiz" stuff at the end of the day.

Unless the vario manual declares the calibration is in "indicated"
units, I've always assumed it's calibrated in true rate-of-climb. I
recall the old mechanical (and maybe the thermistor flow sensor
varios), flow driven vane-type varios did read "indicated", but for
decades, varios have used pressure sensors and I think they are
calibrated in "actual rate of climb".


--
Dan, 5J