En route glide slope?

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

On Fri, 19 Nov 2004 15:08:56 -0500, Andrew Gideon
wrote:

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?

Not trying to be argumentative, but a simple look at the altimeter
provides all the info you need to know. I do not see much value add
by having a GS needle tell me I am 100 feet too high (enroute), when I
can look at the altimeter and get the same info.

Another issue: The setting of the enroute cruise altitude introduces
an opportunity for error - where the pilot sets the wrong cruise
altitude.

Of course, this issue already exists with the more advanced altitude
preset autopilots. I wonder if setting the wrong altitude is a
problem with those?

-Nathan

Nathan Young wrote:

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

Not trying to be argumentative, but a simple look at the altimeter
provides all the info you need to know.

Even more to the point, a look at the altimeter provides you with the
correct information, namely pressure altitude.

Stefan

"Stefan" wrote in message
...
Nathan Young wrote:

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

Not trying to be argumentative, but a simple look at the altimeter
provides all the info you need to know.

Even more to the point, a look at the altimeter provides you with the
correct information, namely pressure altitude.


Uh... Stefan..., a look at the altimeter provides you with *indicated*
altitude. It only shows *pressure* altitude if the altimeter setting is set
to 29.92

Andrew,
The software on my Pocket PC provides you with a highway in the sky if
you feed it the altitude you want for each leg.
Michelle

Andrew Gideon wrote:

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




--

Michelle P ATP-ASEL, CP-AMEL, and AMT-A&P

"Elisabeth" a Maule M-7-235B (no two are alike)

Volunteer Pilot, Angel Flight Mid-Atlantic

Volunteer Builder, Habitat for Humanity

Icebound wrote:
"Stefan" wrote in message
...

Nathan Young wrote:


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

Not trying to be argumentative, but a simple look at the altimeter
provides all the info you need to know.

Even more to the point, a look at the altimeter provides you with the
correct information, namely pressure altitude.



Uh... Stefan..., a look at the altimeter provides you with *indicated*
altitude. It only shows *pressure* altitude if the altimeter setting is set
to 29.92


Sounds like his enroute flight takes place above FL 180

Dave

Many, if not most, turbine airplanes have this but it requires an airdata
computer system. You can set it to arrive at a particular point at a
specific altitude. You need an airdata system as long as you are climbing
or descending to a pressure altitiude. WAAS could only guide you to a GPS
altitude.

Mike
MU-2


"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

"Icebound" wrote in message
...

"Stefan" wrote in message
...
Nathan Young wrote:

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

Not trying to be argumentative, but a simple look at the altimeter
provides all the info you need to know.

Even more to the point, a look at the altimeter provides you with the
correct information, namely pressure altitude.


Uh... Stefan..., a look at the altimeter provides you with *indicated*
altitude. It only shows *pressure* altitude if the altimeter setting is
set to 29.92

All altitudes shown on an altimeter are "pressure altitudes" (as opposed to
true altitudes) since the altimeter is an air pressure guage marked in feet.

Mike
MU-2

"Mike Rapoport" wrote in message
k.net...
Many, if not most, turbine airplanes have this but it requires an airdata
computer system. You can set it to arrive at a particular point at a
specific altitude. You need an airdata system as long as you are climbing
or descending to a pressure altitiude. WAAS could only guide you to a GPS
altitude.


Does it really drive the glideslope needle?

Some of the more sophisticated GPSs have VNAV functionality, and turbine
aircraft FMSs almost certainly do too, based on a barometric altitude input.
But I always thought there was a reluctance to put the information on the GS
needle because the glideslope of an ILS is generally associated with a
trajectory with terrain clearance -- something that simple VNAV can't
guarantee.

Julian Scarfe

Icebound wrote:

Uh... Stefan..., a look at the altimeter provides you with *indicated*
altitude. It only shows *pressure* altitude if the altimeter setting is set
to 29.92

Uh... Icebound..., the altimeter *always* indicates pressure altitude.
To get useful information, you must set the altimeter appropriately, of
course. Appropriately may or may not mean 1013.

On the other hand, your GPS always gives you GPS altitude, which is of
no value in flight.

Stefan