On Mar 18, 9:47*am, Darryl Ramm wrote:

And the issue there is that most SN10s will be installed with the
static connected to the ship's static (that's what the manual says,
and is probably best for accurate wind calculations etc.) and AFAIK is
not able to display any pressure altitude delivered via NMEA from an
attached IGC flight recorder. So the SN10 is normally not sensing
cockpit ambient and unable to report what any attached IGC flight
recorder is sensing.

Hopefully the take away here is more allow a saftey margin and do soem
tests before hand rather than watch some stupid display while killing
yourself and others at a finish.

Darryl

Ugh - now I have to go run experiments to see what generates the
lowest cockpit ambient pressure across different speeds and vent
configurations.

Since the official altitude for finishes is the logger baro altitude I
just fly that. I guess I could worry about the 100 feet or so of
pressure error - it's worth maybe 15-20 seconds in theory. If I were
going to reset my logger's altimeter I'd want to do it at the start of
my final glide, not the end. I suppose it would be okay for the CD to
call altimeter setting in addition to winds for finishers, but I'm not
sure it's worth the trouble.

Also, I don't recall whether my computer uses baro or GPS altitude for
calculating final glides, but it has never been so far off from the
logger baro readout that I can't just do what UH suggests in the last
mile or so - bleeding off speed to hold altitude as indicated by the
302 display, which is quite easy to scan.

The comments by UH, BB and others are REALLY important - staying on a
predictable track during the last part of final glide is a critical
safety practice. Thrashing around when you are low and fast is a
recipe for something really bad.

Also, an evil thought occurred to me - does Winscore check to see
whether you reset the logger altimeter between when you finish and
when you land? It strikes me you could finish really low then crank
the altimeter setting down 500 feet before you land. I'd guess someone
thought of that already and eliminated that opportunity for mischief.

9B