Tony this is something I also heard of.
I use Garmins and when signal is lost it says "signal lost". That's it. When
I enter a tunnel it says "signal lost" within 3 seconds.
Same happens on SirfIII chipsets. Even if a device interpolates a signal
between two known points in a period of a few second, that's a straight line
and I can't see what kind of advantage it could hold. I say "a few seconds",
cause after a few seconds if signal is lost it is lost! And that's for sure.
Garmin and modern GPS chipsets are much more accurate and reliable then
older chipset used inside (f.i.) LX.
I have seen (and can demonstrate) logs by LX-20 that show a standard Cirrus
flying at almost 800km/h (like a Boeing 737).
Expecially while banking at 45 degrees these devices (old chipsets) tend to
loose signal and the firmware (gps firmware) sends incorrect data. This is a
statement, it's logged. You can see a glider jumping like a rabbit with
10-15km steps!
So what is the point with interpolation on a straight line (if at all it is
done, I do not any evidence of this) in 2-3 seconds?
At least a Garmin will always report correct coordinates. I suspect many old
LX do not in certain circumstances. Fact is that IGC is not declaring these
devices unreliable. (clearly I talk about LX but generally I guess any
other device with some 8-10 years life).
So if it is not important that official loggers are precise, I can't
understand why a COTS should - given the fact that all evidences show that
newer chipsets are times more accurate then older.

The only issue should be that a garmin can be "tampered" (theoretically),
while an official flight recorder cannot.
So use a COTS under supervision of an officer and that's all (just like with
cameras).

I think that it is time that someone at IGC take in consideration what
pilots say, and not only what IGC approved manufacturers want and say.



"Tony Burton" ha scritto nel messaggio
...
One of the restrictions on the use of COTS units for Silver and Gold badge
flights (assuming that
their use is approved at the upcoming IGC annual meeting), is that units
that have a dead reckoning
function on loss of signal may be used unless the function can be
disabled. I have been hold that
Garmin units have this function but that it cannot be disabled, which
would disqualify them. Does
anyone have any facts on this?