Can a failed Glide Slope also void the Localizer approach?

On Thu, 24 Aug 2006 04:20:06 GMT, Jose wrote:

All of those have a separate LOC procedure, which cannot be switched to midsstream.

Why could one not switch midstream? Assuming the LOC course is the
same, if the GS goes out, fly level until the next stepdown.

Jose

That's not a bad question. But easily answered if you look at the charts. I
didn't look at all of them, but perhaps if you examined the BFI ILS Rwy 13R
approach, or the KMSO ILS RWY 11 approach, you would understand.
Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

but perhaps if you examined the BFI ILS Rwy 13R
approach, or the KMSO ILS RWY 11 approach, you would understand.

Well, maybe I'm thick, but I don't understand. True, you need to be
prepared to switch (i.e. have the chart handy, have the DME tuned
properly) but I see no reason why a properly prepared pilot could not
switch. True, you may be below the stepdown fix when you lose the GS,
but if you don't go any lower, you won't hit anything (the GS has
already provided obstacle clearance) and you should be able to fly your
present altitude until the next stepdown.

Or... set up for the LOC, but fly the GS if it's available.

I'm looking right now at the BFI ILS 13R and the LOC/DME for the same
runway.

Jose
--
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Jose wrote:
Well, maybe I'm thick, but I don't understand. True, you need to be
prepared to switch (i.e. have the chart handy, have the DME tuned
properly) but I see no reason why a properly prepared pilot could not
switch.
Or... set up for the LOC, but fly the GS if it's available.
I'm looking right now at the BFI ILS 13R and the LOC/DME for the same
runway.

Try looking at the BTM ILS 15 and LOC/DME for the same runway, and it
will be a lot clearer. You can't set up for the LOC and use GS if
available, because the procedures for setting up are not the same. On
the ILS, you intercept the GS at 10,600, at 14+ DME from I-BEY. On the
LOC/DME, you can be down to 9600 at that point. Even if you do pull
that off (and it can certainly be done - at least the intercept is from
below), there is another reason you can't do it. The missed approach
for the ILS has you climbing to 11,000. On the LOC/DME, it's only
9,200. Might be iffy if the controller has someone holding at CPN at
11,000 or something similar.

There certainly are situations (BFI ILS 13 and LOC/DME comes to mind)
where the approaches are sufficiently similar that you could do it
safely, but that's not how the regulations work. If you are cleared
for one approach, you can't just change your mind and do another,
because there is no requirement to design them such that the change is
safe - and BTM is one example where the change is NOT safe. Therefore,
you are cleared for one given approach (unless given a cruise clearance
or explicitly cleared for any approach) and you must obtain an amended
clearance if you want to change your mind.

In those situations where the approaches are on the same plate (say
ILS/LOC or VOR/GPS or some such) the approach clearance covers whatever
is on the plate for which you have the equipment, and thus you can make
the change midstream if you so choose since the design of the approach
is such that the change is safe.

Michael

On Thu, 24 Aug 2006 15:01:06 GMT, Jose wrote:

but perhaps if you examined the BFI ILS Rwy 13R
approach, or the KMSO ILS RWY 11 approach, you would understand.

Well, maybe I'm thick, but I don't understand. True, you need to be
prepared to switch (i.e. have the chart handy, have the DME tuned
properly) but I see no reason why a properly prepared pilot could not
switch. True, you may be below the stepdown fix when you lose the GS,
but if you don't go any lower, you won't hit anything (the GS has
already provided obstacle clearance) and you should be able to fly your
present altitude until the next stepdown.

Or... set up for the LOC, but fly the GS if it's available.

I'm looking right now at the BFI ILS 13R and the LOC/DME for the same
runway.

Jose


What Michael wrote.
Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

Jose wrote:
All of those have a separate LOC procedure, which cannot be switched to midsstream.

Why could one not switch midstream? Assuming the LOC course is the
same, if the GS goes out, fly level until the next stepdown.

Jose


It is fine to switch mid stream. Looking at the BTM approach, I suspect
the only reason the LOC and ILS are published as separate charts is
because several significant differences in IAF, glideslope intercept
altitude and Missed Procedures. The chart would be way too cluttered if
presented on one sheet.

Jose wrote:
All of those have a separate LOC procedure, which cannot be switched
to midsstream.


Why could one not switch midstream? Assuming the LOC course is the
same, if the GS goes out, fly level until the next stepdown.

Jose

They are on separate charts with separate titles because they are
sufficiently different to defy making a clear chart.

Jim Carter wrote:
I had a question today that I’ve never considered, and need the
experience of the group.



Are there airports with ILS approaches such that if the Glide Slope
component failed or went OTS, the entire approach would be un-executable
by regulation? I’ve always assumed that with the GS OTS I’d just revert
to the LOC, but are there approaches were the full ILS is approved but
the LOC only isn’t? In other words, are there precision approaches where
vertical guidance is required and there is no non-precision alternative?



There are some procedures that only have precision ILS minima published
on the procedure, so if the GS went OTS, then that procedure would not
be available simply because that procedure requires the glideslope and
has no LOC line of minima. If they have circling minima on the ILS then
there is a note "Circling requires descent on glideslope to MDA".
See the example at Butte, Montana;
http://www.naco.faa.gov/d-tpp/0608/00588I15.PDF
In that example, there is no non-precision alternative on that
particular plate, but there is a LOC procedure published on a separate
approach plate if you want to fly the LOC only procedure.
I don't know offhand if there are any ILS runways that have no "LOC
only" mins available at all.

JPH

JPH wrote:

I don't know offhand if there are any ILS runways that have no "LOC
only" mins available at all.

JPH

KMSO