ILS critical area when the tower is closed?

"Mark Hansen" wrote in message
...

I'm not sure that's the only time it's a problem. It just the minimum
that the tower is required to keep the area clear. I would expect that
ILS can be interfered with regardless of the current weather.


Certainly, but if the weather's good how is that a problem?

It may be the localizer that you are interfering with, not only the GS.



Roy Smith wrote:
Mark Hansen wrote:


Well, if it's only a problem when an aircraft is on the ILS and it's below
800/2, and given that ATC isn't going to release an IFR departure if an
aircraft is on the ILS, then it doesn't appear to be a problem.

I'm not sure that's the only time it's a problem. It just the minimum
that the tower is required to keep the area clear. I would expect that
ILS can be interfered with regardless of the current weather.


I think the idea is that even a distorted GS will be accurate enough to get
you to within 800/2 of the runway.

AIM Figure 2-3-16? If there are taxiway markings for an ILS critical area,
and the departing pilot knows that the weather is even close to 800-2, s/he
doesn't have to depend on a controller for instructions. The controlling
authority (in the absence of a controller) knows what the situation with
regards to inbounds is and can advise the departing pilot if there is
someone on the way in. "Hold short of runway 16, traffic on two mile final."

Bob Gardner

"Mark Hansen" wrote in message
...
On 11/20/2005 12:41 PM, Bob Gardner wrote:

I don't see what the tower being open or closed has to do with it. They
don't shut down the ILS when the last controller goes home, and a plane
in the restricted area distorting the glideslope signal is not a good
thing.

Sure. But the tower is the controlling authority which is instructing
planes to hold clear of the ILS critical area.

If the tower is not in operation, who gives the order?

If the pilot on the ground is supposed to know when to hold clear,
how does he know? He may not even know a plane is using the
ILS. And besides, the tower only needs to keep it clear when the
weather is below 800/2, so does this go for the non-towered airport
as well?

Where is this defined?


Bob Gardner

"Mark Hansen" wrote in message
...
In this month's AOPA Flight Training magazine, I read an article
which implied there was still some requirement to remain clear of
the ILS critical area even when the tower was closed.

I've been looking through the AIM, and can't find anything like
this. It does say that when the tower is open, it will keep the
area clear when there is an aircraft past the FAF and the weather
is below 800/2.

Is there a rule which states that the ILS critical area must be
kept clear at any time when the tower is not in operation?

Can you please provide a reference?

Thanks,

--
Mark Hansen, PP-ASEL, Instrument Airplane
Sacramento, CA




--
Mark Hansen, PP-ASEL, Instrument Airplane
Sacramento, CA

Isn't the localizer antenna down at the other end of the runway? If a pilot
is departing from the end, the localizer signal should be 700 feet wide at
that point.

Bob Gardner


Bob Gardner

"Newps" wrote in message
. ..
It may be the localizer that you are interfering with, not only the GS.



Roy Smith wrote:
Mark Hansen wrote:


Well, if it's only a problem when an aircraft is on the ILS and it's
below 800/2, and given that ATC isn't going to release an IFR departure
if an aircraft is on the ILS, then it doesn't appear to be a problem.

I'm not sure that's the only time it's a problem. It just the minimum
that the tower is required to keep the area clear. I would expect that
ILS can be interfered with regardless of the current weather.


I think the idea is that even a distorted GS will be accurate enough to
get you to within 800/2 of the runway.

"Bob Gardner" wrote in message
...

AIM Figure 2-3-16? If there are taxiway markings for an ILS critical area,
and the departing pilot knows that the weather is even close to 800-2,
s/he doesn't have to depend on a controller for instructions. The
controlling authority (in the absence of a controller) knows what the
situation with regards to inbounds is and can advise the departing pilot
if there is someone on the way in. "Hold short of runway 16, traffic on
two mile final."


What is the controlling authority in the absence of a controller?

"Bob Gardner" wrote in message
news

Isn't the localizer antenna down at the other end of the runway? If a
pilot is departing from the end, the localizer signal should be 700 feet
wide at that point.


They're at opposite ends of the runway and you're not going to interfere
with both of them simultaneously, but your taxi route may take you through
both of them.

How many fields are there where this is a concern? I would expect most
fields with the congestion to require marked ILS critical areas to have
full-time towers.

In article ,
Roy Smith wrote:

Mark Hansen wrote:
In this month's AOPA Flight Training magazine, I read an article
which implied there was still some requirement to remain clear of
the ILS critical area even when the tower was closed.

The reason you're supposed to keep clear of the ILS critical area is
because your airplane can affect the glide slope beam. The presence or
absence of somebody in the tower doesn't change the physics of how
microwaves interact with metallic bodies.

The glideslope signal is reflected off the ground. The structure that
houses the GS antenna is located far enough down the runway so that the
GS signal is bounced off the ground approximately 1000 feet from the
approach end of the runway. If you look, you will notice the ground is
quite flat and level where the signal is reflected. An object,
especially metal, which intrudes in the space between the antenna and
the runway threshold at the approach end of the runway may distort the
GS signal.

"Mark Hansen" wrote in message
...
In this month's AOPA Flight Training magazine, I read an article
which implied there was still some requirement to remain clear of
the ILS critical area even when the tower was closed.

I've been looking through the AIM, and can't find anything like
this. It does say that when the tower is open, it will keep the
area clear when there is an aircraft past the FAF and the weather
is below 800/2.

Is there a rule which states that the ILS critical area must be
kept clear at any time when the tower is not in operation?

Can you please provide a reference?

Maybe no rule but good airmanship should keep you out of the critical area
if its required.

On 11/20/2005 2:54 PM, Bob Gardner wrote:

AIM Figure 2-3-16?

Sorry I wasn't clear, Bob. I wasn't asking where the hold short
or ILS markings were or how they were depicted at the airport.


If there are taxiway markings for an ILS critical area,
and the departing pilot knows that the weather is even close to 800-2, s/he
doesn't have to depend on a controller for instructions. The controlling
authority (in the absence of a controller) knows what the situation with
regards to inbounds is and can advise the departing pilot if there is
someone on the way in. "Hold short of runway 16, traffic on two mile final."

Just who is going to say "Hold short" when the tower is closed?

Perhaps the only time you have to worry about the ILS critical area
is when the weather is below 800/2, in which case only IFR departures
will be of concern, and they won't get their clearance unless the
airspace is clear.

Assuming the weather is above VFR minimums, VFR arrivals and departures
could interfere with the ILS system, and there appears to be no protocol
to prevent that, since any airplane using the system isn't depending on it
to get to minimums anyway?

Well, I guess I have my answer.


Bob Gardner

"Mark Hansen" wrote in message
...
On 11/20/2005 12:41 PM, Bob Gardner wrote:

I don't see what the tower being open or closed has to do with it. They
don't shut down the ILS when the last controller goes home, and a plane
in the restricted area distorting the glideslope signal is not a good
thing.

Sure. But the tower is the controlling authority which is instructing
planes to hold clear of the ILS critical area.

If the tower is not in operation, who gives the order?

If the pilot on the ground is supposed to know when to hold clear,
how does he know? He may not even know a plane is using the
ILS. And besides, the tower only needs to keep it clear when the
weather is below 800/2, so does this go for the non-towered airport
as well?

Where is this defined?


Bob Gardner

"Mark Hansen" wrote in message
...
In this month's AOPA Flight Training magazine, I read an article
which implied there was still some requirement to remain clear of
the ILS critical area even when the tower was closed.

I've been looking through the AIM, and can't find anything like
this. It does say that when the tower is open, it will keep the
area clear when there is an aircraft past the FAF and the weather
is below 800/2.

Is there a rule which states that the ILS critical area must be
kept clear at any time when the tower is not in operation?

Can you please provide a reference?

Thanks,

--
Mark Hansen, PP-ASEL, Instrument Airplane
Sacramento, CA




--
Mark Hansen, PP-ASEL, Instrument Airplane
Sacramento, CA




--
Mark Hansen, PP-ASEL, Instrument Airplane
Sacramento, CA

On 11/20/2005 3:56 PM, Chris wrote:

"Mark Hansen" wrote in message
...
In this month's AOPA Flight Training magazine, I read an article
which implied there was still some requirement to remain clear of
the ILS critical area even when the tower was closed.

I've been looking through the AIM, and can't find anything like
this. It does say that when the tower is open, it will keep the
area clear when there is an aircraft past the FAF and the weather
is below 800/2.

Is there a rule which states that the ILS critical area must be
kept clear at any time when the tower is not in operation?

Can you please provide a reference?

Maybe no rule but good airmanship should keep you out of the critical area
if its required.



How does the pilot know it is required if not told to keep clear of
the area by the control tower?

--
Mark Hansen, PP-ASEL, Instrument Airplane
Sacramento, CA