IFR hold short line at uncontrolled airports?

"Peter R." wrote in message
...

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?


Towered fields tend to have more operators to accommodate so they have more
ramp space and taxiways, thus a greater opportunity to enter critical areas.



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


And if it can't be passed by an aircraft on a taxiway it isn't a problem.
If access to the runway is from just one side and the glideslope transmitter
is on the far side of the runway it can't be passed by an aircraft on a
taxiway. That's the situation you find at most uncontrolled fields.

"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---

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

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 in message ...


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.

Of course, the localizer is off the end of the runway. The glideslope is in the
vicinity of the touchdown zone. Since they don't last too long if they stick then
in the touchdown zone, you've got at least two possibilities for siting (one on each
side of the runway).

"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.

In article k.net, "Steven
P. McNicoll" writes:

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


And if it can't be passed by an aircraft on a taxiway it isn't a problem.
If access to the runway is from just one side and the glideslope transmitter
is on the far side of the runway it can't be passed by an aircraft on a
taxiway. That's the situation you find at most uncontrolled fields.


A story why you need a safety pilot. I was on a practice ILS at KLPR ( a non
towered airport) and the glide slope needle was "right on". Safety pilot said,
"Chuck, take off your hood, you are getting pretty low." We sure were, but no
glideslope flag. Advance power and as we over fly the field, we see that they
are mowing around the antenna. Now on any ILS, I like to be one mark high on
the glideslope. ILS runways are long for my Archer and it better insures that
all is OK.

Chuck

"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.

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