"Richard Kaplan" wrote in message news:1095562995.6eAYDxNjAfSfAEnPws5pJw@teranews. ..
"C Kingsbury" wrote in message
om...

With WAAS underway, it seems predictable that non-precision approaches
will be joining colored airways in the dustbin of history. If the FAA

This is unlikely when one considers that a number of airports which
currently have WAAS approaches have non-precision minimums which are lower
than the WAAS minimums.

Hmmm, is this just a matter of the TERPS guys being conservative until
WAAS is better understood? I can't see any case where WAAS provides
poorer positional accuracy than a VOR, and it should at least be very
close to the performance of a localizer.

Also consider that WAAS approaches can only be designed to airports clear of
obstructions according to TERPS; thus lots of airports will remain eligible
only for non-precision approaches.


Heh. Good point, I hadn't thought about that so much.

Actually, an interesting case-study can be seen looking at the
different approaches for Rutland, VT
(http://www.airnav.com/airport/KRUT) which is down in a valley with a
gaggle of towers. With its proximity to several major ski resorts it
gets a fair deal of light bizjet traffic.

Approach | Minima AGL (all straight-in)
===========|=============
LOC 19 | 2100
VOR-DME 19 | 1800
GPS 19 | 1400
LOC+DME 19 | 900

According to these plates, the angle of descent in the final segment
ranges between 3.35-3.72 degrees, as compared to a 3deg standard ILS.

Is there any reason why using WAAS, it wouldn't help to basically
setup a virtual glideslope that brings the plane down to the minimum
at the appropriate point, and then "levels off" until the missed
approach point? Well, other than the fact that perhaps no one has
thought about designing such a procedure, I suppose...

Still, at the very least every airport should be able to support
minimums equivalent to those that would be provided by a LOC-DME
installation. You can't change the dictates of terrain but at least
you don't have to pay to install and maintain a shed full of radio
equipment.

Best,
-cwk.