On Sun, 10 Jul 2005 11:45:48 -0400, Brad Zeigler wrote:

Hi Brad,

See below comments. Keep in mind, I consider myself still new at
instrument flying. Followups set to rec.aviation.ifr to maintain on topic.

Its not a big deal if you realize that ATC isn't going to give your exact
distance.

1) ATC is not responsible for calibrating your DME.

Agree 100 percent

2) ATC assumes you will be able to figure out when you cross the VOR

Agree 100 percent. That's what the to and from flags are for. So, the
distance to the VOR did not concern me as I had the flags to help me
identify the fix nor did I need a timer to verify the fix as I was being
vectored.

3) This specific approach can use time to identify the MAP

This is where I have additional questions. The time is based on a distance
factor. The actual approach is the VOR A at MBO. I need 3 minutes 20
seconds to fly 5 miles from the JAN VOR to the MAF.

Add in a headwind on the approach IF I have a discrepancy between what ATC
is reporting and what my DME says, then I would think there is a potential
problem, especially if ATC is reporting that I am closer then what my DME
says.

I do use all possible tools in my plane, and I do have a VFR GPS to help me
determine ground track, so I can tell whether I should arrive to the MAP
sooner or later then 3.20, but if didn't have that, wouldn't the accuracy
of the DME be more critical since time would be skewed by wind correction?

Now, by posting my concern to the newsgroup, I think I am learning that the
DME would be an overriding factor on "who to trust" for distance
determination. As I posted before, I never had come across a discrepancy
before between my DME and what ATC reported.

Hopefully I am right on my assumption that the DME is the overriding
decision for accuracy??

Allen