KJZI (Charleston Executive, S.C.) ILS RWY 9 DME Required

On Mar 12, 9:41*am, Robert Moore wrote:
" *wrote

It's pretty clear that we're not supposed to go below the published MDA on
a non-precision approach, unless we can see enough to descend and land. The
MAP has nothing to do with it except that we can't continue the approach to
land after reaching the MAP.

Bob,

Bear with me on this. Are you suggesting or saying it's ok to go
below MDA BEFORE the MAP????

I was taught NEVER to descend below DH for the ILS or MDA before the
MAP for non precision approaches such as VOR alpha or LOC.

My point to Sam was that timing alone with wind consideration is not
enough to descend below MDA which again I was taught never descend
below BEFORE the MAP.

DME is the constant factor to finding MAP on this approach, not timing
since there are no intersecting radials to identify MAP.

Timing helps but since GS will vary based on wind conditions, timing
ALONE shouldn't be used to determine MAP.

This is what I was taught for what it's worth.

For what it is worth, I am instrument rated, and current, and I am with Sam
on this one. You are indeed expected to know what your ground speed is on
final, within a reasonable margin of error, and the timing table (or your
own time/speed calculation) is the correct way to determine the MAP. There
are plenty of LOC approaches without DME, and not that many that actually
require it. The minimums applied here, along with the penalties for no
local altimeter etc are plenty conservative to make this a safe LOC
approach without DME. It could simply be a charting mistake.

If they really meant for DME to be required it would likely be in the name;
ILS or LOC/DME RWY 9.




In article
,
says...



But of course you do know that the timing table is based on GS. * What
if your GS was 68 knots Sam?

DME is your ONLY source to ensure that you are at MAP along WITH
timing. * If you want to descend below MDA based on time alone AND no
DME, I sure wouldn't want to fly with you.

Of course I do NOT know that. *The timing table is for the LOC MAP. *DA
is your MAP for the ILS.

This newsgroup is so lacking in the fundamentals.

You imply Sam that timing alone is how you determine the MAP. I say
it's not.

DME determines when you can go below MDA which would be at MAP not 3
minutes 12 seconds.

Be my guest on descending below MDA at 3:12 without DME Sam. I won't
be in the plane with you as you come up short or even overshoot the
MAP due to headwinds or tailwind considerations.

VOR-DME wrote:

For what it is worth, I am instrument rated, and current, and I am with Sam
on this one. You are indeed expected to know what your ground speed is on
final, within a reasonable margin of error, and the timing table (or your
own time/speed calculation) is the correct way to determine the MAP. There
are plenty of LOC approaches without DME, and not that many that actually
require it. The minimums applied here, along with the penalties for no
local altimeter etc are plenty conservative to make this a safe LOC
approach without DME. It could simply be a charting mistake.

If they really meant for DME to be required it would likely be in the name;
ILS or LOC/DME RWY 9.

No, that is not correct. Several years ago the naming convention was
changed to include DME in the title only when it is required for the
final approach segment. If it is required for the intermediate segment,
or all of initial approach segments (if there is more than one) or the
missed approach segment, it will be a note.

In the case of the procedure that started this thread, DME is required
for the missed approach holding fix, because the crossing radial does
not pass flight inspection below 6,000. The crossing radial should not
be shown in that case, but the procedures staff keeps it on there hoping
that maintenance will eventually get it fixed so they remove the DME
note. Yes, convoluted and confusing.