At 07:30 29 December 2004, Eric Greenwell wrote:

I think the pilots trying this are not doing that,
but instead rely on
their airspeed to give them IAS. This does require
calibration of the
ASI for real accuracy.

Actually the first post in this thread (from Mark)
read:

'Has anyone done any work to develop a program that
would look at some flight logs and determine what a
particular glider's actual polar is?'

This original idea has now morphed into a suggestion
essentially to replicate the technique used by Dick
Johnson and others, with the main difference being
using the barometric altitude transducer in a flight
computer instead of the mechanical altimeter(?). This
might offer some improvement in accuracy, but is at
least as complex to execute as the flight test techniques
used for the past 40+ years.

There are two main challenges with using flight logs
only:

1) There is no good source for IAS, so you have to
try to estimate it from GPS ground speed.

2) Typical soaring flights don't involve adequately
calm vertical airmass movement and probably not constant
enough airspeed to trust even long glides of many tens
of miles.

9B