IFR hold short line at uncontrolled airports?

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

The longer runways are more likely to have critical areas.

Why?

Jose

--
(for Email, make the obvious changes in my address)

Teacherjh wrote:
The longer runways are more likely to have critical areas.


Why?

The localizer will be closer to the (opposite) runway threshold.


All the best,


David

In article
ogers.com,
David Megginson wrote:

Teacherjh wrote:
The longer runways are more likely to have critical areas.


Why?

The localizer will be closer to the (opposite) runway threshold.


All the best,


David

Why should runway length affect how far the localizer antenna is from
the runway end?

Localizers are designed to have a fixed width (something like 700 ft
lateral displacement for full-scale deflection on the CDI) at the
arrival threshold, so longer runways will have narrower angular beam
widths. But (to the best of my knowledge) this is done by adjusting the
spacing of the transmitting elements on the localizer array, not by
adjusting the distance of the array from the runway end.

Localizers are designed to have a fixed width (something like 700 ft
lateral displacement for full-scale deflection on the CDI) at the
arrival threshold, so longer runways will have narrower angular beam
widths.


Doesn't make sense to me. Angular beam width should be constant - for the far
field. Then the antenna is placed at the distance from the arrival end (also
constant) that gives the proper width.

No?

Jose



--
(for Email, make the obvious changes in my address)

"David Megginson" wrote in message
le.rogers.com...

The localizer will be closer to the (opposite) runway threshold.


So what?