Altitude Encoder w/ GPS Question

Dave S wrote:
Ron Natalie wrote:
Scott Rodriguez wrote:

Looking at buying an altitude encoder for the transponder in my
yet-to-be-born homebuilt.

I see some altitude encoders have an RS-232 output for sending altitude
information to a GPS. What kind of functionality does this provide?
Is it
"real-world" useful?

It's required for IFR approach certification I believe.

Negative. The encoder can be used to provide altitude alerting functions
through the gps, but it's not precise enough for providing vertical
guidance in an approach. The typical serial encoder reports in 100 ft
increments.

Did I say SQUAT about vertical guidance. It is a requirement for
TSO-C129a CERTIFICATION. I didn't say what it was used for.
My statement appears to still hold true.

Ron Natalie wrote:


Did I say SQUAT about vertical guidance. It is a requirement for
TSO-C129a CERTIFICATION. I didn't say what it was used for.
My statement appears to still hold true.

ARRGGGHHH!!!..

You are ABSOLUTELY CORRECT. The altitude source must be connected in
order to have an IFR certified installation. It even states as such in
my King KLN-89B installation manual. I missed those 2 sentences previously.

The irony of it is, I've got the wires installed for it on mine, even
though the only discernable function is the altitude alert, which I'm
not sure I'm going to use.

Thanks Ron.. I was wrong and you were right.

"Dave S" wrote in message
ink.net...
Ron Natalie wrote:


Did I say SQUAT about vertical guidance. It is a requirement for
TSO-C129a CERTIFICATION. I didn't say what it was used for.
My statement appears to still hold true.

ARRGGGHHH!!!..

You are ABSOLUTELY CORRECT. The altitude source must be connected in order
to have an IFR certified installation. It even states as such in my King
KLN-89B installation manual. I missed those 2 sentences previously.

The irony of it is, I've got the wires installed for it on mine, even
though the only discernable function is the altitude alert, which I'm not
sure I'm going to use.

Thanks Ron.. I was wrong and you were right.

The RAIM algorithm in the GPS needs the BARO input. It's only required use
is to support the integrity monitor. The altitude alert is a 'feature' that
King added for marketing (value-added) reasons. It cost them almost nothing
per unit and just a few thousand $ of non-recurring costs to develop the
software.

Gerry