NACO charts - why have a reference circle?

On Sat, 06 Sep 2003 00:39:13 -0000, Phil Verghese
wrote:

That's what got me measuring distances on the charts and discovering
that things even outside the reference circle are actually to scale. By
the way, NACO charts are the same scale as a sectional (when the
reference circle is 10 NM).

[snip]

So my contention is the reference circle doesn't really show anything,
and I find it distracting. I think I can safely ignore it. Please
correct me if you feel that is unsafe to just ignore the reference
circle.

I was never interested enough to measure myself, but it may be a
"guarantee" issue. The word isn't really used but I think what the
circle is telling you is that NACO vouches for the accuracy of the
terrain/obstruction information within the circle and not outside of
it.

Can you safely ignore it? The reality is that most of the obstruction
information is "nice to know stuff." For flying the approach, all you
really need are the frequency, course, altitude, and distance/time
numbers. So, the obstruction/terrain information probably doesn't
really matter much.

It's when you get into trouble (engine problem that requires that you
get on the ground now) that you want to know where the terrain and
obstructions are. so, based on pilot input, you get charts with
terrain in as much detail as Jepp. Less for flying the approach than
for general situational awareness and emergency use. Can you safely
ignore it then? I guess that depends on the nature of the problem and
your personal analysis of whether the risk of the information being
wrong is worth it.



Mark Kolber
APA/Denver, Colorado
www.midlifeflight.com
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