why is intercept altitude labeled "LOC only"?

"Sam Spade" wrote in message
...
But, the two altitude designations when they are the same is incorrect,
redundant, and has the potential for some confusion.

I agree that it's redundant, confusing, contrary to the chart-design rules,
and shouldn't be done. My only point is that at least nothing in the SWF ILS
9 chart is overtly false (whereas the LOC-only annotation for the
GS-intercept altitude in the ASH ILS 14 chart is indeed false; if it were
true, there'd be no specified GS-intercept altitude for the ILS approach).

--Gary

Gary Drescher wrote:
"Sam Spade" wrote in message
...

But, the two altitude designations when they are the same is incorrect,
redundant, and has the potential for some confusion.


I agree that it's redundant, confusing, contrary to the chart-design rules,
and shouldn't be done. My only point is that at least nothing in the SWF ILS
9 chart is overtly false (whereas the LOC-only annotation for the
GS-intercept altitude in the ASH ILS 14 chart is indeed false; if it were
true, there'd be no specified GS-intercept altitude for the ILS approach).

--Gary


Yes, one is bad, the other is worse. ;-)

Sam Spade wrote:



Here is what is said in the original issuance of 8260.19C, dated 9/16/93
( Page 8-11, Paragraph 811 d.):

(1) Fix altitudes established on ILS for LOC-only should be coincident
with the glide slope when possible. Where the stepdown fix altitude is
not within 20 feet of the glide slope, annotate it for LOC use as follows:

MIN ALT CAROL 1600^
*LOC ONLY

This is the same as it reads today, for all practical purposes.

Can you cite the language that changed this for some period between late
1993 and today?

The language is the NOTE that was added in change 1 to clarify that if
the glideslope intercept altitude and LOC altitude at the FAF are the
same, then you only publish the one altitude.
The above language says "within 20 ft of the glideslope" and not "within
20 ft of the glideslope intercept altitude". On the ASH ILS Rwy 14
procedure, although the glideslope intercept altitude is 1800, the
actual glideslope altitude at CHERN LOM is 1586, which is more than 20
ft different than the LOC alt at CHERN LOM of 1800.
Since the fix altitude of 1800 was not within 20 ft of the glideslope at
CHERN LOM, the procedure specialist added "1800 LOC ONLY" on the FAA
procedure form in addition to the 1800 glideslope intercept altitude.
Both altitudes should have been shown (as they are at SWF) but only one
was charted.
The FAA form for this particular procedure was done before the
clarification came out.
Actually, the 20 ft part of this paragraph really only applies to
stepdown fixes inside the LOC FAF, these days if the glideslope altitude
at the LOM was 1750, and the glideslope intercept altitude and LOC
altitude at the LOM was 2000, you still wouldn't show a "LOC ONLY"
altitude at the FAF, even though the paragraph mentions "20 ft".
However, if the stepdown altitude inside the LOC FAF (which only applies
to LOC procedures) is not within 20 ft of the glideslope altitude at the
stepdown fix, you have to add the "LOC ONLY" annotation to avoid the
potential for someone on the glideslope thinking they have to stop
descent until they pass the stepdown fix. The added NOTE is what applies
to the altitudes outside the FAF.

JPH