"Don Faulkner" wrote in message
news

Hi folks. I've got a bit of a puzzle here.
First off, I'm a student pilot, so maybe I haven't gotten to this yet.

Take a look at the ILS 18 plate for Springdale, AR (ASG):
http://myairplane.com/databases/appr...l/ASG_ir18.pdf

First, note that the approach is "ILS RWY 18"
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Next, read in the notes section:
Circling NA east of Rwy 18-36, inoperative table does not apply.
DME from RZC VORTAC
Simultaneous reception of I-ASG and RZC DME required.
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So, the way I read this, DME is not required, since the approach is ILS
not ILS DME, but it is required since "simultaneous reception ... is
required."

I guess my real question is, "Is this approach authorized for an aircraft
without DME? And if not, why don't they call it ILS-DME?" but read on for
my thinking...

Looking at the chart, here are the uses of DME that I see:
1. DME arcs to intercept the localizer
2. A 3.8 DME non-precision MAP (my Jepp plate shows a non-precision decent
with DME 3.8 as the MAP)
3. WESTY intersection, 18 DME out, which can also be identified by a
cross-radial from the DAK VOR.

Now, this is how I reason (i.e. rationalize. my way out of these:
1. I tune the RZC VORTAC and fly the DME ARC, but once I turn to intercept
the localizer, I no longer care about the ARC, so I don't need DME
anymore.
2. DME would be helpful here, and simultaneous reception would be
required, but I could also time from the FAF to identify the MAP.
3. I can swap VOR receivers once safely established on missed approach, so
I shouldn't need this for the inbound part of the approach.

To my thinking, #2 is the shakiest logic. Still, if DME is required, why
don't they just call it an ILS-DME approach?


Looks to me like the only portion of this approach that requires DME is the
8 DME arc to the localizer. If you're going to fly this procedure you must
be able to receive the localizer and DME from RZC VORTAC simultaneously. To
fly it without simultaneous reception would require you to tune and identify
the localizer upon reaching one of the lead radials. Not an impossible
task, but one that can be rather distracting and possibly vertigo-inducing.
I have an old chart book with a previous version of this approach, Amdt 6A,
that does not have this simultaneous reception requirement. It appears
somebody thought it was a good thing to add.

There are a couple of curious things about this approach. What is the
purpose of TINSE and how does one identify it? I looked up TINSE in the
Location Identifiers book, it's 8 DME from RZC on the localizer, but you
couldn't tell that from the plate. What is the purpose of "2800 NoPT (7.5)"
just inside of the arc? I see only three ways to get to that point once
inbound on the localizer; via the arc which is already designated NoPT, via
radar vectors which by regulation prohibit a PT, or after already having
completed a PT.