Intercepting the ILS

wrote:
Roy Smith wrote:

wrote:

Yesterday I was out getting an IPC. We were doing the Stockton, CA
ILS. ATC had us intercepting the localizer at 2000 feet. The
altitude for glideslope interception is 1800 ( underlined ).
[...]
The new CFII criticized this procedure and told me that the plate
specified 1800, and it was wrong to intercept at 2000.


I can't see any reason not to intercept at 2000. I think your new guy
is full of it.

As a matter of regulation, the G/S is to be used as primary vertical
guidance only from the PFAF inbound. There are some places, where early
use of the G/S has resulted in airspace violations, LAX being the most
notable.

Let's be argumentative here. What regulation are you referring to?
In the case of LAX (the Civet 4 arrival I quoted earlier), the
problem was that following the glideslope caused the airplane to
violate published crossing restrictions.

In the case cited, the CFI is nitpicking but is nonetheless legally correct.

At SCK there was no crossing restriction either given in the
clearance or published. The pilot is free to descend *at his
discretion* from 2000 to 1800. Following the glideslope is a perfectly
acceptable way of doing that. The CFI is not only nit-picking, but in
this instance is wrong. Not only that, but he's making additional
unnecessary work.

We intercepted at 3000 and rode it down more out of inertia than anything
else. We did have a "maintain 2200" instruction while at three but not a
"descend and maintain." As I recall, I was coming from the northwest and had
picked up the localizer 20 miles or so out. Three is pretty popular around
here for the lowest altitude prior to an approach, and in retrospect I think
the controller just wanted me to make a hole for someone else to fit into.
Gotta admit I felt a little sheepish about getting called on it because I
knew better.
"Garner Miller" wrote in message
...
In article , Bob Gardner
wrote:

FWIW, I have been chewed out by Seattle Approach for intercepting higher
than the published GSIA of 2200 for the ILS 13R.

Nevermind the "Which airport" question if my cancel didn't work, I
found it; Boeing field, I assume.

I can't see why they would have chewed you out -- if the instruction
was something like "Maintain 2500 until established on the localizer,
cleared the ILS 13R," you did nothing improper. If he wanted you at
2200, he should have instructed you to do so; the chart only lists it
as a minimum altitude, as most do.

What if you weren't DME-equipped? How would you know you were within
10NM of NOLLA, and thus safe to descend to 2200? You really wouldn't,
unless you had done the procedure turn, or the controller had cleared
you with a "You're X miles from NOLLA" (and X happened to be less than
10 miles).

--
Garner R. Miller
ATP/CFII/MEI
Clifton Park, NY =USA=
http://www.garnermiller.com/

wrote:
Hello,

Yesterday I was out getting an IPC. We were doing the Stockton, CA
ILS. ATC
had us intercepting the localizer at 2000 feet. The altitude for
glideslope
interception is 1800 ( underlined ).

My old CFII taught me that the glideslope interception altitude on
the chart is a minimum altitude, and that it was fine to intercept it
higher. So I just tootled along
at 2000 - figuring it was simpler to do one configuration change at GS
interception
rather than three changes - one to descend the 200 feet, another to
level off, and
a third to intercept the glideslope.

The new CFII criticized this procedure and told me that the plate
specified 1800,
and it was wrong to intercept at 2000. Which one was right?

My first thought was, "your old CFII" was right.

I certainly would have done exactly what you did, and had no heartburn over it.

OTOH, that got me wondering how much above the published glide slope intercept
altitude I would accept. To take an extreme example to illustrate the question
(not a realistic example, of course) suppose ATC had you intercepting the
localizer at 10000 feet.

For the purposes of the thought experiment, assume this still allows you to
intercept the glide slope from below. Could you be confident that the glide
slope had been flight-checked up to 10000 feet? No. You also don't know that
it's been flight checked to 2000 feet. Where do you draw the line?

Dave

On 01/26/06 11:14, Dave Butler wrote:
wrote:
Hello,

Yesterday I was out getting an IPC. We were doing the Stockton, CA
ILS. ATC
had us intercepting the localizer at 2000 feet. The altitude for
glideslope
interception is 1800 ( underlined ).

My old CFII taught me that the glideslope interception altitude on
the chart is a minimum altitude, and that it was fine to intercept it
higher. So I just tootled along
at 2000 - figuring it was simpler to do one configuration change at GS
interception
rather than three changes - one to descend the 200 feet, another to
level off, and
a third to intercept the glideslope.

The new CFII criticized this procedure and told me that the plate
specified 1800,
and it was wrong to intercept at 2000. Which one was right?

My first thought was, "your old CFII" was right.

I certainly would have done exactly what you did, and had no heartburn over it.

OTOH, that got me wondering how much above the published glide slope intercept
altitude I would accept. To take an extreme example to illustrate the question
(not a realistic example, of course) suppose ATC had you intercepting the
localizer at 10000 feet.

For the purposes of the thought experiment, assume this still allows you to
intercept the glide slope from below. Could you be confident that the glide
slope had been flight-checked up to 10000 feet? No. You also don't know that
it's been flight checked to 2000 feet. Where do you draw the line?

Dave

The other thing to remember is that when you are backed-up from the
Final Approach Point, you know you will intercept the GS at a higher
altitude, but where exactly? After all, if you are too high, you
could be picking up an erroneous echo of the GS signal.

This is part of the risk (minor that it is) in doing this - because
if you follow the signal down to the outer marker (in the OP's case)
and are not at the correct GS altitude, you probably should go missed.

However, in the real world, ATC isn't going to vector you in this way
if the altitude wouldn't intercept the actual GS signal, so although
the pilot should remain vigilant and watch for things to go south, it will
generally work out.

--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

In article 1138302691.662580@sj-nntpcache-5, Dave Butler
wrote:

...suppose ATC had you intercepting the localizer at 10000 feet.

For the purposes of the thought experiment, assume this still allows
you to intercept the glide slope from below. Could you be confident
that the glide slope had been flight-checked up to 10000 feet? No.
You also don't know that it's been flight checked to 2000 feet. Where
do you draw the line?

You draw the line by looking at the profile view on the approach chart,
ensuring that you're above the step-downs as the appropriate point.
(One some approaches, as other posters noted, the glideslope will put
you below some of these crossing restrictions. Fuzzy memories tell me
BOS ILS27 used to be like that, but it isn't anymore.)

As long as you're cross-checking your altitudes to ensure you're above
the minimum crossing altitudes, there's no problem at all following the
glideslope down from farther out. It's *vitally* important to check
the glideslope crossing altitude at marker, of course, to ensure that
you're not on a false glideslope.

--
Garner R. Miller
ATP/CFII/MEI
Clifton Park, NY =USA=
http://www.garnermiller.com/

As long as your resulting flight path complies with your clearance
and the published altitude restrictions on the approach plate, you are
free to descend at your discretion. If that just happens to follow the
apparent glideslope, valid or not, it is immaterial.
You only get into trouble if following the glideslope causes you to
violate an altitude restriction.

On Thu, 26 Jan 2006 09:29:10 -0800, wrote:



As a matter of regulation, the G/S is to be used as primary vertical
guidance only from the PFAF inbound. There are some places, where early
use of the G/S has resulted in airspace violations, LAX being the most
notable.

In the case cited, the CFI is nitpicking but is nonetheless legally correct.

Huh? What regulation?

Published guidance in the AIM indicates that the GS is generally usable out
to ten miles, but this may be extended at certain locations.




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

wrote:


As a matter of regulation, the G/S is to be used as primary vertical
guidance only from the PFAF inbound. There are some places, where early
use of the G/S has resulted in airspace violations, LAX being the most
notable.

In the case cited, the CFI is nitpicking but is nonetheless legally
correct.

Tim,

Can you give an example of how an airspace violation could occur? It
seems that as long as the pilot doesn't descend below the minimum
altitude published for the segment of the approach he's in, then
descending on the glidepath can't put the aircraft any lower than
dropping down immediately to the minimum segment altitude at the
beginning of the segment. If he's in the Intermediate, then the
glidepath will more than likely keep him higher than dropping down to
the minimum altitude due to the length of the intermediate normally
compensating for the required altitude loss at 150 ft per mile optimum.
If the airspace violation would be from the aircraft being too high,
then perhaps the procedure should have a maximum altitude shown or the
controller issue a crossing restriction.
The glideslope intercept altitude is a minimum altitude, not a mandatory
or maximum altitude. From a TERPS standpoint there's no problem with
descending on the glideslope from 2000 on the procedure in question
instead of 1800.
If the pilot uses the glideslope for backup vertical guidance to give a
smooth transition to the final segment (while using the altimeter
readout outside the FAF to ensure he doesn't descend below 1800) then
what's wrong with that?

JPH

JPH wrote:

Can you give an example of how an airspace violation could occur? It
seems that as long as the pilot doesn't descend below the minimum
altitude published for the segment of the approach he's in, then
descending on the glidepath can't put the aircraft any lower than
dropping down immediately to the minimum segment altitude at the
beginning of the segment. If he's in the Intermediate, then the
glidepath will more than likely keep him higher than dropping down to
the minimum altitude due to the length of the intermediate normally
compensating for the required altitude loss at 150 ft per mile optimum.
If the airspace violation would be from the aircraft being too high,
then perhaps the procedure should have a maximum altitude shown or the
controller issue a crossing restriction.

It's happen at LAX quite a few times when the air is hot and the
underlying Ontario airspace rises to provide less than 1,000 feet of
vertical on the LAX G/Ses. The G/S doesn't move.

The glideslope intercept altitude is a minimum altitude, not a mandatory
or maximum altitude. From a TERPS standpoint there's no problem with
descending on the glideslope from 2000 on the procedure in question
instead of 1800.

True enough, and if the pilot wants to remain above the G/S that is
perfectly legal. But, any charted minimum stepdown altitudes prior to
the PFAF are governing, not the G/S.

If the pilot uses the glideslope for backup vertical guidance to give a
smooth transition to the final segment (while using the altimeter
readout outside the FAF to ensure he doesn't descend below 1800) then
what's wrong with that?

Nothing wrong with that.

wrote:

wrote:

Roy Smith wrote:



Let's be argumentative here. What regulation are you referring to?
In the case of LAX (the Civet 4 arrival I quoted earlier), the
problem was that following the glideslope caused the airplane to
violate published crossing restrictions.

In the Los Angeles case the violations occurred inside the CIVET
arrival, actually on the ILS profile. Those fixes are issued under Part
97 just as it the legal point at which the G/S *controls* for
descent(the PFAF).

In the case cited, the CFI is nitpicking but is nonetheless legally correct.


At SCK there was no crossing restriction either given in the
clearance or published. The pilot is free to descend *at his
discretion* from 2000 to 1800. Following the glideslope is a perfectly
acceptable way of doing that. The CFI is not only nit-picking, but in
this instance is wrong. Not only that, but he's making additional
unnecessary work.


I agree that the CFI is procedurally wrong, although legally correct.
Let me put it another way: the CFI is stuck on one aspect of the issue,
the other being that the pilot can make certain elections so long as he
does not use the G/S as primary for descent prior to the PFAF. The CFI
has a duty to teach resonable procedure while pointing out the legal
nuances of when the G/S is primary for altitude control. It sounds like
he covered only one aspect of the issue, which while correct legally, is
incorrect and out of context procedurally.