IFR hold short line at uncontrolled airports?

Peter R. wrote:

Matt Whiting ) wrote:


The ILS antenna doesn't know if the field has a control tower or not.
If an ILS hold is needed, then the taxiway would be marked.


And conversely, if ILS hold short lines are needed at most towered
airports, why are they not needed everywhere? What makes certain ILS
arrangements prone to interference and others not?

It seems to me that any ILS antenna that can be passed by an aircraft on
a taxiway would be prone to interference.


I suspect it has to do with the location of the antenna. I don't they
they are all located in exactly the same spot WRT to the runway.


Matt

"Matt Whiting" wrote in message
...



I suspect it has to do with the location of the antenna. I don't they
they are all located in exactly the same spot WRT to the runway.

The glideslopes are as they are all positioned to bring you to the same spot
on every runway. The localizer is sited so it is a certain width at the
approach end of the runway, therefore they will move the localizer antenna
closer to or farther away from the departure end of the runway to achieve
that.

"Newps" wrote in message =
...
=20
"Matt Whiting" wrote in message
...

I suspect it has to do with the location of the antenna. I don't =
they
they are all located in exactly the same spot WRT to the runway.
=20
The glideslopes are as they are all positioned to bring you to the =
same spot
on every runway. The localizer is sited so it is a certain width at =
the
approach end of the runway, therefore they will move the localizer =
antenna
closer to or farther away from the departure end of the runway to =
achieve
that.
=20

By far the most impressive localizer antenna I've ever seen
is on the top of Aspen Mountain, aimed out across the Pitkin County =
Airport
and the valley beyond to the northwest.
It's an array of, I think, sixteen rugged Yagis over an expanded-metal =
screen.
However, I doubt that localizer course width at any threshold was a =
factor
in the design of this particular installation. It's for missed =
approaches only.
---JRC---

On Wed, 26 May 2004 17:13:43 -0600, "Newps" wrote:

The glideslopes are as they are all positioned to bring you to the same spot
on every runway.

Well, not exactly. The glide slope transmitter is located between 750
feet and 1,250 feet from the approach end of the runway (down the runway)
and offset 250 to 650 feet from the runway centerline.

And it can be on either side of the runway.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

"Ron Rosenfeld" wrote in message
...

And it can be on either side of the runway.


And if there's a taxiway on just one side of the runway, the GS transmitter
tends to be on the other side of the runway.

Newps wrote:

"Matt Whiting" wrote in message
...



I suspect it has to do with the location of the antenna. I don't they
they are all located in exactly the same spot WRT to the runway.


The glideslopes are as they are all positioned to bring you to the same spot
on every runway. The localizer is sited so it is a certain width at the
approach end of the runway, therefore they will move the localizer antenna
closer to or farther away from the departure end of the runway to achieve
that.



Then why do some runways have ILS critical areas and others do not?

Matt

"Matt Whiting" wrote in message ...

Then why do some runways have ILS critical areas and others do not?

All runways have an ILS critical area. The issue is whether there is a taxiway that passes
through it or not.

"Ron Natalie" wrote in message
. ..

All runways have an ILS critical area.


Actually, it's just those with an ILS. And runways with a full ILS have two
critical areas, a Localizer Critical Area and a Glideslope Critical Area.



The issue is whether there is a taxiway that passes through it or not.


To help illustrate this I've posted two figures from FAA Order 6750.16,
"Siting Criteria for Instrument Landing Systems", in
alt.binaries.pictures.aviation. The subject is ILS Critical Areas.

Ron Natalie wrote:

"Matt Whiting" wrote in message ...

Then why do some runways have ILS critical areas and others do not?


All runways have an ILS critical area. The issue is whether there is a taxiway that passes
through it or not.


My home airport, N38, doesn't. :-)


Matt

The longer runways are more likely to have critical areas. Runways whose
taxiways get too close to the runway is also a factor. We have that problem
here at BIL. The last 3000 feet of taxiway angles in toward the runway
creating the need for an ILS hold area because you get in the way of the
localizer.



"Matt Whiting" wrote in message
...
Newps wrote:

"Matt Whiting" wrote in message
...



I suspect it has to do with the location of the antenna. I don't they
they are all located in exactly the same spot WRT to the runway.


The glideslopes are as they are all positioned to bring you to the same
spot
on every runway. The localizer is sited so it is a certain width at the
approach end of the runway, therefore they will move the localizer
antenna
closer to or farther away from the departure end of the runway to
achieve
that.



Then why do some runways have ILS critical areas and others do not?

Matt