Andy Blackburn wrote:

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.

This data is available from various instruments, like the Cambridge 302
that I use. For the 302 it's actually the TAS, which could be combined
with the air temperature and pressure altitude to compute the IAS. The
TAS and temperature are not recorded in the 302 flight log,
unfortunately, but they could be recorded by the Ipaq connected to it
and inserted in the flight log it keeps, and this log used for the analysis.


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.

I think this is a show-stopper, even if the IAS is available in a flight
log.
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Eric Greenwell
Washington State
USA