ILS X Approach

B

barunal

Guest
Dear all,

My name is Baris.
I'm not a pilot but a great fan!
I came across term ILS X approach over the internet.
Thought you guys could give me a basic explanation of it.
How does it differ from regular ILS approaches?
Thanks a lot.

Baris Unal
barunal@hotmail.com
 
Barunal:

First off, welcome to PoA- tell us about yourself!

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Secondly, when you have an approach which is identified with a letter rather than a runway, it means the approach gets you to the airport environment, but does not take you to a runway with precision. Example: http://204.108.4.16/d-tpp/0913/06644VDA.PDF

I have never heard of an "ILS" which did not lead to a runway, but there's a lot I have never heard of, isn't there? I am familiar with LDA (Localizer Displaced Array) approaches, so I might speculate you could have an ILS to a place other than a runway, if it included glideslope information as well as localizer. If you can post a sample of the plate, we might all comment more (and I can learn yet another thing I should know but don't).
 
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dmccormack said:
Maybe because they are few and far between?

:yesnod:

(The local DPE has one on his home airport -- guess what every IR candidate has to perform?)
Click to expand...

Here's my favorite of the LDAs that I've shot:

http://204.108.4.16/d-tpp/0913/00443LDAD19.PDF

Requires a bit of threading the needle, especially there at the end; no transgression allowable to the left of the loc, and a tight, low altitude turn to runway. But man, what a view when you're riding in the back!

And here's the one I've shot during every checkride for the last three years (and quite a few times for real).
http://204.108.4.16/d-tpp/0913/00289LDAA.PDF


For the OP, here's an example (thanks to Google) of lettered ILS approachs. Though not located domestically, they use the same system of naming that we do.

http://www.opennav.com/pdf/RJTT/JP-AD-2.24.48-RJTT-en-JP.pdf
http://www.opennav.com/pdf/RJTT/JP-AD-2.24.47-RJTT-en-JP.pdf


EDIT: Sorry Mari, I didn't see your post. This is what happens when I see something shiny while I'm in the middle of typing.
 
Teller1900 said:
Here's my favorite of the LDAs that I've shot:

http://204.108.4.16/d-tpp/0913/00443LDAD19.PDF

Requires a bit of threading the needle, especially there at the end; no transgression allowable to the left of the loc, and a tight, low altitude turn to runway. But man, what a view when you're riding in the back!

And here's the one I've shot during every checkride for the last three years (and quite a few times for real).
http://204.108.4.16/d-tpp/0913/00289LDAA.PDF.
Click to expand...

Are you requesting those? Otherwise, what's the point on runways already served with an ILS?
 
Everskyward said:
Yeah, but I think there would have to be three to get to the letter X since they work backwards down the alphabet. Here is an example of Y and Z.

http://naco.faa.gov/d-tpp/0913/00504ILY19.PDF

http://naco.faa.gov/d-tpp/0913/00504ILZ19.PDF
Click to expand...

You could have an X without both a Y and a Z if the Y or Z had originally been published (or at least prepared) but no longer exists.

And to the OP, in the case of an ILS (a precision approach that provides vertical and horizontal guidance to a runway using spatially coded directional radio transmissions) there would always be a runway number (the runway heading in tens of degrees) along with the 'X' in the approach title, e.g. "ILS X RWY 25"
 
dmccormack said:
Are you requesting those? Otherwise, what's the point on runways already served with an ILS?
Click to expand...

No. DCA doesn't have a precision approach to any of their southbound runways (19/15), so the LDA DME 19 is just about the only way to get in when they're on southbound flow with low ceilings. Usually you start out on the LDA, then transition to the River Visual once you get low enough to see the Potomac.

LGA uses the LDA-A quite often when the ILS 22 isn't working or, if memory serves, as an alternate approach to get to 31, which isn't served by an ILS. We use it in the sim as one of our required non-precision approaches.
 
dmccormack said:
Then I'd still opt for a LOC approach.. takes you to the runway with typically lower mins...
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An LDA is a LOC approach, just not aligned with the runway. In the case of DCA, an actual LOC isn't an option as it would take you right through the middle of P-56 (actually, right through the middle of the Washington Monument). That tends to end badly for flight crews and pax.
 
Teller1900 said:
An LDA is a LOC approach, just not aligned with the runway. In the case of DCA, an actual LOC isn't an option as it would take you right through the middle of P-56 (actually, right through the middle of the Washington Monument). That tends to end badly for flight crews and pax.
Click to expand...

:rofl:
 
Teller1900 said:
An LDA is a LOC approach, just not aligned with the runway.
Click to expand...
IIRC, they may or may not have up to double the course width allowed for LOC approaches.
In the case of DCA, an actual LOC isn't an option as it would take you right through the middle of P-56 (actually, right through the middle of the Washington Monument). That tends to end badly for flight crews and pax.
Click to expand...
:yikes:
 
gismo said:
IIRC, they may or may not have up to double the course width allowed for LOC approaches.
Click to expand...

I think you're thinking of an SDF. AIM 1-1-9c1.: "The LDA is of comparable use and accuracy to a localizer, but is not part of a complete ILS. The LDA course usually provides a more precise approach course than the similar Simplified Directional Facility (SDF) installation, which may have a course width of 6 or 12 degrees. 2.The LDA is not aligned with the runway. Straight-in minimums may be published where alignment does not exceed 30 degrees between the course and runway. Circling minimums only are published where this alignment exceeds 30 degrees.
 
gismo said:
You could have an X without both a Y and a Z if the Y or Z had originally been published (or at least prepared) but no longer exists.
Click to expand...
That is true too.

Speaking of LDA approaches, I remember that I took this picture recently because I was having trouble explaining to someone in another thread what the Jepp charts in the airplane look like. I hope that person is viewing this thread too.

In this picture we were going direct VOAXA so that's how the little green airplane is oriented while the chart just looks like a chart with north up. The reason the header is at the bottom is that this is the split screen view. If you look at the radio buttons at the top you can select "header", "profile" or "minima" to be displayed down there.
 

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