On Mon, 25 Oct 2004 18:52:13 GMT, "John R. Copeland"
wrote:

"Ron Rosenfeld" wrote in message ...
On Sun, 24 Oct 2004 23:57:17 GMT, "John R. Copeland"
wrote:

However, I have not (yet) found in the pilot's manual any
explanation of when VDI drive is withheld from an external HSI.
By flying several different kinds of approaches, I seem to see
that the external VDI will be active *only* when VNAV minima apply.
Only on precision approaches having DH instead of MDA,
my autopilot could arm and capture the glideslope,
exactly the same as an ILS.
On non-precision approaches my external VDI needle remained
driven out of view, even though its glide-slope flag was pulled,
and as a result I could not arm the glide slope for automatic capture.

John,

I won't be upgrading my CNX80 until the end of December, but in Newsletter
5 from Garmin there is a description indicating that Glideslope guidance
should be available on your HSI for LNAV/VNAV, LPV *and* "non-precision
approaches with defined vertical paths" so long as the HPL or VPL minimums
for the approach are not exceeded.

Perhaps something has changed since that document was written; or perhaps
there's a glitch in your wiring.

--ron

Ron, I no longer have newsletter 5, but I can't fault the newsletter announcing
availability of the version 2 upgrade, because the new NAV display in the
CNX-80 performs as the attachment to that newsletter described.
For LNAV approaches, I have not found where that attachment promised
glide-path guidance on an external indicator, only on the internal NAV display.

The undocumented part concerns the drive to the external VDI in my flight director.
Wiring can't be faulty, because it works flawlessly on ILS and VNAV approaches.
My avionics installer promised today to inquire about that with his factory rep.
If I get clarification, I'll share it here.
---JRC---

Perhaps I misunderstood your original post.

I didn't see anything in either promising external VDI signals for an LNAV
approach unless it fell into the category of being a non-precision approach
with associated vertical path data. (And which could therefore include
other types of non-precision approaches).

There is an extra explanatory paragraph in newsletter 5.

-----------------------
Attachment:

Glideslope guidance for LNAV/VNAV (Gamma 2) and LPV (Gamma 3) approaches,
and advisory vertical guidance for other non-precision approaches with
vertical path data associated with them.

-------------------------------------

Newsletter 5:

Glideslope guidance for LNAV/VNAV (Gamma 2) and LPV (Gamma 3) approaches,
and advisory vertical guidance for other non-precision approaches with
vertical path data associated with them.

We’ve discussed this feature in the newsletter before and here are some
nuts and bolts. All LNAV/VNAV and LPV approaches as well as non-precision
approaches with defined vertical paths will have vertical guidance
displayed on your HSI or CDI. This will drive the CDI and VDI and they will
behave as they would during an ILS approach.

--------------------------------------


--ron