BAF LOC 23

[Paul Tomblin]

I'm trying to figure out the BAF ILS 23 localizer approach. The normal
LOC 23 approach has a MDA of 900, and the LOC 23/DME approach has a MDA of
700 feet. After the FAF, there is a step down fix at 2.7 DME with a
_1160_ before it. So does this mean that if you don't have DME, you can
descend to 900 immediately after the FAF, but if you do have DME you can
only descend to 1160 until 2.7 DME? Why is it safe to descend to 900 in
one case, but only 1160 in the other?

--
Paul Tomblin > http://xcski.com/blogs/pt/
My family's values included "Always state your assumptions and your evidence",
"first find out what the problem is, then fix it", and "feed your horse before
yourself". But you don't see people legislating those... -- Zeebee

[Ben Jackson]

In article >,
Paul Tomblin > wrote:
>I'm trying to figure out the BAF ILS 23 localizer approach.

BAF??

--
Ben Jackson
>
http://www.ben.com/

[David Rind]

Paul Tomblin wrote:
> I'm trying to figure out the BAF ILS 23 localizer approach. The normal
> LOC 23 approach has a MDA of 900, and the LOC 23/DME approach has a MDA of
> 700 feet. After the FAF, there is a step down fix at 2.7 DME with a
> _1160_ before it. So does this mean that if you don't have DME, you can
> descend to 900 immediately after the FAF, but if you do have DME you can
> only descend to 1160 until 2.7 DME? Why is it safe to descend to 900 in
> one case, but only 1160 in the other?
>

Assuming you mean CEF, not BAF, it does seem to read that way. I agree
it seems odd.

--
David Rind

[Paul Tomblin]

In a previous article, David Rind > said:
>Paul Tomblin wrote:
>> I'm trying to figure out the BAF ILS 23 localizer approach. The normal
>> LOC 23 approach has a MDA of 900, and the LOC 23/DME approach has a MDA of
>> 700 feet. After the FAF, there is a step down fix at 2.7 DME with a
>> _1160_ before it. So does this mean that if you don't have DME, you can
>
>Assuming you mean CEF, not BAF, it does seem to read that way. I agree
>it seems odd.

Oh yeah, CEF. Wrong bookmark.


--
Paul Tomblin > http://xcski.com/blogs/pt/
http://www.pointlesswasteoftime.com/film/50reasons.html
"Apparently they made the beasts [Uruk Hai] by crossing Orcs, Goblins and
the French."

[zatatime]

On Sun, 10 Oct 2004 20:37:11 +0000 (UTC),
(Paul Tomblin) wrote:

>I'm trying to figure out the BAF ILS 23 localizer approach. The normal
>LOC 23 approach has a MDA of 900, and the LOC 23/DME approach has a MDA of
>700 feet. After the FAF, there is a step down fix at 2.7 DME with a
>_1160_ before it. So does this mean that if you don't have DME, you can
>descend to 900 immediately after the FAF, but if you do have DME you can
>only descend to 1160 until 2.7 DME? Why is it safe to descend to 900 in
>one case, but only 1160 in the other?


I may be completely wrong on this, but I think the 1160 is a step down
for both types. As I see it if you have DME you can proceed lower (to
700) at the 2.7 mile mark, otherwise the radar facility will call the
2.7 mile position for you at which time you can proceed lower to 900.
This may allow for the radar facility to be more inaccurate than the
on board DME. The approach does say Radar Required.

Also, If you proceed to 700 you'll go missed at .9 DME, where as if
you don't have DME. all you have is time. I think they might also
want some added safety for some reason (possibly for clearance of the
390 foot obstacle right near the end of the runway).

There's also 923 foot obstacle just left of course after the FAF that
I'd be very careful to stay above, and is what made me initially think
the 1160 was for both approaches.

Hope this helps. Looking forward to further discussion on this one.

z

[Brad Z]

"zatatime" > wrote in message
...
> I may be completely wrong on this, but I think the 1160 is a step down
> for both types. As I see it if you have DME you can proceed lower (to
> 700) at the 2.7 mile mark, otherwise the radar facility will call the
> 2.7 mile position for you at which time you can proceed lower to 900.
> This may allow for the radar facility to be more inaccurate than the
> on board DME. The approach does say Radar Required.

....except the step-down fix doesn't include the words "RADAR", indicating
that the controller will call the stepdown.

Come to think of it, I doubt they'd have a radar fix inside the FAF because
at that point, you'd be on or switching to tower, which may or may not have
a radar display in the cab.

Interesting.

[Gary Drescher]

"zatatime" > wrote in message
...
> On Sun, 10 Oct 2004 20:37:11 +0000 (UTC),
> (Paul Tomblin) wrote:
>
>>I'm trying to figure out the BAF ILS 23 localizer approach. The normal
>>LOC 23 approach has a MDA of 900, and the LOC 23/DME approach has a MDA of
>>700 feet. After the FAF, there is a step down fix at 2.7 DME with a
>>_1160_ before it. So does this mean that if you don't have DME, you can
>>descend to 900 immediately after the FAF, but if you do have DME you can
>>only descend to 1160 until 2.7 DME? Why is it safe to descend to 900 in
>>one case, but only 1160 in the other?
>
> I may be completely wrong on this, but I think the 1160 is a step down
> for both types. As I see it if you have DME you can proceed lower (to
> 700) at the 2.7 mile mark, otherwise the radar facility will call the
> 2.7 mile position for you at which time you can proceed lower to 900.

That's how I read it too. An MDA doesn't override a prior minimum altitude.
Without radar, there's no way to descend below 1160' (except visually).

Cool example--thanks for posting it, Paul!

--Gary

[Gary Drescher]

"Brad Z" > wrote in message
news:grjad.224521$D%.88524@attbi_s51...
> "zatatime" > wrote in message
> ...
>> I may be completely wrong on this, but I think the 1160 is a step down
>> for both types. As I see it if you have DME you can proceed lower (to
>> 700) at the 2.7 mile mark, otherwise the radar facility will call the
>> 2.7 mile position for you at which time you can proceed lower to 900.
>> This may allow for the radar facility to be more inaccurate than the
>> on board DME. The approach does say Radar Required.
>
> ...except the step-down fix doesn't include the words "RADAR", indicating
> that the controller will call the stepdown.

Hm, good point. So maybe there's no way to use the non-DME MDAs.

> Interesting.

Indeed. :)

--Gary

[Paul Tomblin]

In a previous article, "Gary Drescher" > said:
>Cool example--thanks for posting it, Paul!

Well, I'm really hoping I'll do the ILS or the visual, but it pays to
prepare.

--
Paul Tomblin > http://xcski.com/blogs/pt/
"It is a universal truth that the loss of liberty will be charged to
dangers, real or imagined, from abroad." - James Madison

[Roy Smith]

In article <grjad.224521$D%.88524@attbi_s51>,
"Brad Z" > wrote:

> "zatatime" > wrote in message
> ...
> > I may be completely wrong on this, but I think the 1160 is a step down
> > for both types. As I see it if you have DME you can proceed lower (to
> > 700) at the 2.7 mile mark, otherwise the radar facility will call the
> > 2.7 mile position for you at which time you can proceed lower to 900.
> > This may allow for the radar facility to be more inaccurate than the
> > on board DME. The approach does say Radar Required.
>
> ...except the step-down fix doesn't include the words "RADAR", indicating
> that the controller will call the stepdown.
>
> Come to think of it, I doubt they'd have a radar fix inside the FAF because
> at that point, you'd be on or switching to tower, which may or may not have
> a radar display in the cab.
>
> Interesting.
>
>

Another strange thing is the missed. I can deal with the "expect radar
vectors" part, but I'm a little confused about the "tracking 228" bit.
I can only assume they mean to track the localizer back course outbound,
but normally they would write that as "climb to 3000 via ICEF back
course" or something like that. Did they really mean 228 heading?

Yet another interesting gotcha is that the DME readouts are all relative
to the CEF VORTAC, not the I-CEF localizer.

[[email protected]]

Paul Tomblin wrote:

> I'm trying to figure out the BAF ILS 23 localizer approach. The normal
> LOC 23 approach has a MDA of 900, and the LOC 23/DME approach has a MDA of
> 700 feet. After the FAF, there is a step down fix at 2.7 DME with a
> _1160_ before it. So does this mean that if you don't have DME, you can
> descend to 900 immediately after the FAF, but if you do have DME you can
> only descend to 1160 until 2.7 DME? Why is it safe to descend to 900 in
> one case, but only 1160 in the other?
>
> --
> Paul Tomblin > http://xcski.com/blogs/pt/
> My family's values included "Always state your assumptions and your evidence",
> "first find out what the problem is, then fix it", and "feed your horse before
> yourself". But you don't see people legislating those... -- Zeebee

That procedure is screwed up.

[Michael]

(Paul Tomblin) wrote
> I'm trying to figure out the BAF ILS 23 localizer approach. The normal
> LOC 23 approach has a MDA of 900, and the LOC 23/DME approach has a MDA of
> 700 feet. After the FAF, there is a step down fix at 2.7 DME with a
> _1160_ before it. So does this mean that if you don't have DME, you can
> descend to 900 immediately after the FAF, but if you do have DME you can
> only descend to 1160 until 2.7 DME? Why is it safe to descend to 900 in
> one case, but only 1160 in the other?

Every time we've had this kind of confusion here about an approach, it
turned out to be a charting error. I'm betting this is too.

There's no way to make sense out of this - it's just wrong.

Michael

[G Farris]

It may not be a charting error, but a discrepancy, duly noted by the mention :

"VGSI and descent gradient not coincident".

See the TERPS manual :

http://av-info.faa.gov/terps/Policies1/TIL99014att.PDF

[[email protected]]

Michael wrote:

> Every time we've had this kind of confusion here about an approach, it
> turned out to be a charting error. I'm betting this is too.

Picking at nits: an error in the procedure, not the folks who make the charts.

>
>
> There's no way to make sense out of this - it's just wrong.

Exactly.

>
>
> Michael

[zatatime]

On Mon, 11 Oct 2004 16:27:23 +0000 (UTC), (G
Farris) wrote:

>It may not be a charting error, but a discrepancy, duly noted by the mention :
>
>"VGSI and descent gradient not coincident".
>
>See the TERPS manual :
>
>http://av-info.faa.gov/terps/Policies1/TIL99014att.PDF


VGSI?? Visual Glide Slope Indicator?? What would one of these be, a
VASI?

TCH?? Threshold Crossing Height??

Acronym finder didn't find them and it would really help understand
what the article is about if I understood the acronyms. This may be
our answer.

Thanks for the link and clarification if you can.

z

[Teacherjh]

TCH means Threshold Crossing Height. I added it to
http://www.acronymsearch.com/
It's also in the AIM.

Jose

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

[zatatime]

On Mon, 11 Oct 2004 16:27:23 +0000 (UTC), (G
Farris) wrote:

>It may not be a charting error, but a discrepancy, duly noted by the mention :
>
>"VGSI and descent gradient not coincident".
>
>See the TERPS manual :
>
>http://av-info.faa.gov/terps/Policies1/TIL99014att.PDF


In reviewing the ILS-23 approach plate, I did not see the above
phrase. Where is it located?

Thanks.
z

[zatatime]

On 12 Oct 2004 02:17:39 GMT, (Teacherjh)
wrote:

>Threshold Crossing Height

Thanks.

That one I though I remembered correctly. VGSI however I'm still not
sure of.

z

[[email protected]]

Visual Glide Slope Indicator; generic term for PAPIs and VASIs. It's in
the AIM.

zatatime wrote:

> On 12 Oct 2004 02:17:39 GMT, (Teacherjh)
> wrote:
>
> >Threshold Crossing Height
>
> Thanks.
>
> That one I though I remembered correctly. VGSI however I'm still not
> sure of.
>
> z

[[email protected]]

If you have the NACO chart note at the top center that this is a USAF developed
procedure, not an FAA procedure.

No doubt it is all screwed up, but getting it fixed is another matter.

Paul Tomblin wrote:

> I'm trying to figure out the BAF ILS 23 localizer approach. The normal
> LOC 23 approach has a MDA of 900, and the LOC 23/DME approach has a MDA of
> 700 feet. After the FAF, there is a step down fix at 2.7 DME with a
> _1160_ before it. So does this mean that if you don't have DME, you can
> descend to 900 immediately after the FAF, but if you do have DME you can
> only descend to 1160 until 2.7 DME? Why is it safe to descend to 900 in
> one case, but only 1160 in the other?
>
> --
> Paul Tomblin > http://xcski.com/blogs/pt/
> My family's values included "Always state your assumptions and your evidence",
> "first find out what the problem is, then fix it", and "feed your horse before
> yourself". But you don't see people legislating those... -- Zeebee

[G Farris]

In article >,
says...
>
> On Mon, 11 Oct 2004 16:27:23 +0000 (UTC), (G
>Farris) wrote:
>
>>It may not be a charting error, but a discrepancy, duly noted by the mention
:
>>
>>"VGSI and descent gradient not coincident".
>>
>>See the TERPS manual :
>>
>>http://av-info.faa.gov/terps/Policies1/TIL99014att.PDF
>
>
>In reviewing the ILS-23 approach plate, I did not see the above
>phrase. Where is it located?


You are correct - That condition only applies to the non-precision approach,
and as such does not answer the basic question.

As the step-down fix would appear to be based on the controlling obstacle of
923', within the primary protected area, (corresponds pretty much to ROC
rounded up to nearest 20') one would expect to see the non DME MDA published
as 1160 as well.

Could it be because the military guys used TACAN approaches? This could
explain why the DME fixes are referenced to the vortac, as pointed out
earlier. Just a guess.

G Faris
>
>Thanks.
>z

[Paul Tomblin]

In a previous article, said:
>If you have the NACO chart note at the top center that this is a USAF developed
>procedure, not an FAA procedure.

Well, John Haggerty at the FAA (Eastern Instrument Procedures branch) saw
this thread, and forwarded my question (correcting my mistake about saying
BAF instead of CEF) and the other question about "track 228" on the missed
approach to Tim Lovell at the USAF (afrc.af.mil). So hopefully either
John will post the answer here, or I'll get CC'ed on the response so that
I can post it here.


--
Paul Tomblin > http://xcski.com/blogs/pt/
What philology luser tried to hang "fear of sameness" on bigotry?
Every time i see the word i want to kick his shins.
-- Pat Wade, on homophobia

[zatatime]

Thanks.


On Tue, 12 Oct 2004 06:06:25 -0700, wrote:

>Visual Glide Slope Indicator; generic term for PAPIs and VASIs. It's in
>the AIM.
>
>

[zatatime]

On Tue, 12 Oct 2004 15:35:03 GMT, (Paul
Tomblin) wrote:

>So hopefully either
>John will post the answer here, or I'll get CC'ed on the response so that
>I can post it here.


That'd be great! I've spent a couple hours trying to figure this one
out, and still don't know how to gt down to 900 feet. :)

Thanks John, and everyone else who's answered my questions.

z

[zatatime]

On Tue, 12 Oct 2004 15:17:40 +0000 (UTC), (G
Farris) wrote:

>You are correct - That condition only applies to the non-precision approach,
>and as such does not answer the basic question.
>
OK. Thanks.
>
>Could it be because the military guys used TACAN approaches?

Its possible, but what would a TACAN give out as information to allow
you down to 900 feet if no DME is on board?

This is an odd one....

z

[[email protected]]

Paul Tomblin wrote:

> In a previous article, said:
> >If you have the NACO chart note at the top center that this is a USAF developed
> >procedure, not an FAA procedure.
>
> Well, John Haggerty at the FAA (Eastern Instrument Procedures branch) saw
> this thread, and forwarded my question (correcting my mistake about saying
> BAF instead of CEF) and the other question about "track 228" on the missed
> approach to Tim Lovell at the USAF (afrc.af.mil). So hopefully either
> John will post the answer here, or I'll get CC'ed on the response so that
> I can post it here.
>

Good for him. He's not the only FAA TERPster to needle the Air Force about it
today.

[[email protected]]

zatatime wrote:

> On Tue, 12 Oct 2004 15:35:03 GMT, (Paul
> Tomblin) wrote:
>
> >So hopefully either
> >John will post the answer here, or I'll get CC'ed on the response so that
> >I can post it here.
>
> That'd be great! I've spent a couple hours trying to figure this one
> out, and still don't know how to gt down to 900 feet. :)
>

You can spend a year trying to figure it out, and will still not have an
answer. ;-)

[[email protected]]

zatatime wrote:

> On Tue, 12 Oct 2004 15:17:40 +0000 (UTC), (G
> Farris) wrote:
>
> >You are correct - That condition only applies to the non-precision approach,
> >and as such does not answer the basic question.
> >
> OK. Thanks.
> >
> >Could it be because the military guys used TACAN approaches?
>
> Its possible, but what would a TACAN give out as information to allow
> you down to 900 feet if no DME is on board?
>

Nope, TACAN operates just like VOR and DME, except it is integreted and is less
prone to errors from close in reflections, such as on big boats.