mprather(at)spro.net
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 Posted: Wed Apr 23, 2008 4:24 pm Post subject: AeroElectric-List Digest: 25 Msgs - 04/22/08 |
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Right on, Bob..
I would argue that using the Dynon as the Txp encoder lowers overall risk
as compared to having a standalone encoder. Even if the baro sensor in
the Dynon isn't "as good" as the one from AmeriKing (yeah right..). For
one thing, should the Dynon display provide the primary altitude
information to the pilot, if the altitude readout gets weird, the pilot
will know it fairly quickly under most circumstances. If the airplane has
a backup Kohlsmann.
With the vast majority of standalone encoders feeding their output only to
the Txp, the pilot won't know there's a problem unless ATC complains.
Many VFR pilots never talk to ATC, but often their airplanes are equipped
and hence must operate transponders squawking altitude. If the encoder
fails the day after they leave the radio shop, they'll fly two years
reporting the wrong altitude to ATC and TCAS boxes before the problem is
detected.. It happens, and apparently it's not generally terribly
hazardous.
My preference would be a Dynon (or something similar) driving the Txp and
a GPS unit that displays altitude data. I realize they won't line up very
closely due to temperature issues, but I'm not worried about being +/-300
ft.
Another idea (which is likely not new/unique) is to have the EFIS compare
the GPS altitude against baro altitude (calculating/compensating for
measured temperature) and flash a warning any time there's a noteworthy
discrepancy. Easy to implement, and will help keep me from forgetting to
enter the proper baro setting into the EFIS (either at flight start or
after having flown several hours - through weather systems). And it
should catch rare cases where the EFIS's baro sensor has gone south -
keeping the Txp data clean.
Regards,
Matt-
| Quote: | Good Evening Skip,
Do you intend to have only the Dynon for altitude information?
I will not be flying IFR without having a standard altimeter for
reference,
but that is part of my risk assessment.
Here is my thought trail.
What harm will befall me if the Dynon sends false information to the
transponder?
Or, --- What harm will befall me if the Dynon does not send any data to
the
transponder?
When I have had a transponder send bad data (From fully certified and
TSO'd
equipment by the way) to the FEDs, they have told me about it and asked
that
I turn off the altitude function.
So far, that has seemed to be within the acceptable risk that I am willing
to take.
Whadda Ya think?
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
628 West 86th Street
Downers Grove, IL 60516
630 985-8502
Stearman N3977A
Brookeridge Air Park LL22
In a message dated 4/23/2008 4:28:31 P.M. Central Daylight Time,
CardinalNSB(at)aol.com writes:
...B) Decide that violation of 91.217 is an acceptable risk and feed the
transponder from the non TSO'd altitude encoder contained in the Dynon
unit.....
Well, how does one decide that the real physical risk of a non-TSO's over
a
TSO product is acceptable? How could I, even if I understood all the tso
testing and general electronics manufacturing business, make fact based
assessments as to the reliability of any electronic equipment unless I
had a lab and
testing lab essentially?
I'm sure there is anecdotal evidence of the Dynon's reliability. And I
understand we might want to behave in ways that mitigate against a single
failure
ruining my day. But in a pinch, what tells me to trust one instrument
over
another in a serious moment, especially when the error is not so great to
be
obvious? Skip
**************Need a new ride? Check out the largest site for U.S. used
car
listings at AOL Autos.
(http://autos.aol.com/used?NCID=aolcmp00300000002851)
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