In article ,
says...

Greg,

It's not up to the Pilot to determine *why* the approach was designed the
way it was, only to correctly interpret the procedure and fly it safely.



Well, I have no objection to that, and certainly no intention of doing
otherwise - however I don't think there's anything wrong with wanting to know
why they look like this.

I'm guessing (I admit I'm guessing) it has to do with terrain avoidance - a
straight-in approach could be published for the ILS, because of the precision
vertical guidance, but the larger tolerance of the non-precision approach does
not allow this, even though a precise vertical profile is published. A VOR
approach, without FAF, or an NDB approach requires 300' of obstacle clearance
in the primary area, 6mi wide at 10nm out. Considering that aircraft can
descend to MDA at different rates within this area, this becomes a lot of
airspace to protect, compared to the ILS. I'm guessing this is why many of
them cannot be drawn straight-in, when an ILS to the same runway can.

That's just my guess though - I was hoping to find more precise information
here.

G Faris