It would require extensive (read expensive) modifications to achieve what
you wish. First of all the CDI is driven by a VHF omni range or Localizer
signal while the GS indicator is driven by a UHF signal from the glide slope
transmitter. In the beginning use of ILS there were 2 separate receivers
to be tuned.... one for the Localizer VHF frequency and one for the GS UHF
frequency. Then they paired up LOC/GS frequencies so that tuning the
localizer automatically tunes for the GS. Much the same way that tuning in
VHF VOR stations automatically tunes the paired UHF tacan DME receiver for
VOR stations that have DME.

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

"Andrew Gideon" wrote in message
online.com...
I was staring at the VOR-head during a flight a while back, and started
wondering why we only use half of it most of the time. Whether by GPS or
VOR, the CDI provides us with lateral navigation. But the glide slope
needle sits unused until the very end of the flight (if then {8^).

Why?

Using older technology, why not have an altitude bug and let the bug and
altimeter feed the GS needle, providing VNAV information en route?

Will WAAS-ified GPSs be able to drive the GS needle en route?

Curiously...

Andrew