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Gary Drescher wrote:
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"Steven P. McNicoll" wrote:

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You are correct. There is no end to what some flight
instructors will dream up or invent. Everything the FAA
does in the world of charting is predicated on IAS.

Not quite everything. The approach timing table uses ground speed.

More correctly, the Jeppesen timing table states ground speed.
NACO does not.

Whether they state it or not, there's nothing but ground speed that they
*could* be using to calculate the time to traverse the stated distance.

For the best accuracy, it obviously has to be ground speed. But, there is
no
requirement to make the necessary calculations to arrive at ground speed.
A
lot of folks over many years have simply treated the timing table values
as
indicated airspace,

Whatever shortcuts pilots may take, the fact remains that the NACO timing
tables do use GS, just as the Jepp tables do. If wind is negligible and CAS
is close to IAS, then of course IAS closely approximates GS, but it's still
GS that's given in the tables.

on the premise there are a lot more important things to do
in the final approach segment than attempt to make conversions.

But why would you wait until the final approach segment to make the
conversion? I consider it part of the approach-briefing to calculate GS from
IAS and reported wind, and to write down the appropriate time to the MAP.

In recent years, RNAV has all-but-eliminated any need to use the timing
table
in any case.

Even if your RNAV is certified for IFR, I think it's still a good idea to
pre-compute your time to the MAP in case your RNAV fails during the
approach.

--Gary