"Udo Rumpf" wrote in message
...
Tim Ward wrote

The hardware isn't cheap, but it's getting cheaper, and the data
reduction
post-flight isn't a trivial problem, either, but it's doable.


Tim,
My knowledge is very limited when it comes to the points you made above.
My L Nav produces the data that is now taken manualy in the test flights.
The GN II is hooked up to my LNav making some of the data available.
All this is set up to be down loaded into my PC flight software.
How much effort would it take for some one experienced in writing this
type
of software to get
the remaining data out of the LNav into the flight recorder, like
temperature, altitude, airspeed?
Regards
Udo

As I understand it (and mind you, I was only there once,blindfolded, and it
was a dark and stormy night), Johnson's method relies on the repeatable
vertical accuracy of a mechanical barometric altimeter and a stopwatch.
That gives him an average sink rate over the period of time. If he's
recording temperature, then maybe he post-processes that to get the true
sink rate and true airspeed.
I don't know what kind of vertical accuracy he gets out of that combination
of panel shaker and altimeter. I know I once had an occasion where the
altimeter indication in a 2-33 dropped about 150 feet when I tapped it with
a finger.
If the vertical accuracy on the LNAV is as accurate as he can get, or
better, then it's probably worthwhile to try to pull the other data. I
suspect that it's not, if it's just consumer-grade GPS altitude information,
or Johnson would be using it.

I haven't looked at the LNAV programming interface, so I don't know how hard
it would be to get the information logged. The developers of Soaring Pilot
seem to be pretty amiable about adding features to the program, though.

Tim Ward