From: "John Barrett" <2thman@olympus.net>
To: "Jack Hickham" <hickham@webtv.net>,
	"Lancair Mail List" <lancair.list@olsusa.com>
Cc: "Gordon Pratt" <InteracSol@aol.com>
Subject: RE: List #34"Wazzup with WAAS?
Date: Tue, 15 May 2001 06:41:42 -0700
Message-ID: <NEBBLABMMLJGBIFPPHBBKECGCCAA.2thman@olympus.net>
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Yes Jack,
My day job is general dentistry.
I think you might be missing the point re WAAS.  Non-precision approaches
allow the pilot to simply descend to a published altitude and then land only
if the runway is in sight when he gets to the approach end of that runway.
The best example would be the standard GPS approaches that are now
commonplace and this seems to be consistent with what you describe below.
The minimums on these approaches are commonly 500ft AGL, much higher than
precision approach minimums.  For a precision approach (typically with
minimums to 200ft AGL) you need a tool in the airplane that provides a
VISUAL glide path you can follow on some instrument or other.   GPS signals
are not accurate enough by themselves to give accurate altitude readout for
a three dimensional picture.  That's where WAAS comes in.  It uses ground
signals to integrate with the accurate two-dimensional position data from
GPS to provide sufficient accuracy in the third dimension (altitude).  The
graphical picture you see on your instrument with this system has yet to be
determined by the FAA (to my knowledge) and the WAAS system has been subject
to major delays because of technical difficulties as I understand it.

Since the EFIS 2000 overlays a topographical database onto both its moving
map AND the primary flight display, you can see accurate derived height
above the ground at any point during a flight, whether enroute or on
approach on both of these screens.  With HITS (highway in the sky) you can
simply fly through a series of circles and rectangles that guide you along
the path of a particular approach.  The picture is three dimensional on the
primary flight display. The precision of this system IS accurate enough to
fly an approach to touchdown and, with the SFS EFIS primary flight display,
the task is a thousand times easier than flying the needles in an ILS
approach.  I'm not suggesting lowering precision approach minimums; I'm
simply describing the accuracy of the system in realistic terms.

I recall my Navy flying days in the late '60s where we were without
autopilot.  GCA's (ground controlled approaches) were the standard precision
approach.  When the ILS needles became available, a few IFR trainer A4's had
those aboard, so I had a chance to see that system early.  (in the few
chances I had to try it out, I couldn't come close to mastering it in a high
performance attack aircraft).  I was lucky enough to get one of the first
Garmin GPS units about 14 years ago I think and I still use it in my spam
can.  It is absolutely incredible the leap forward this system provides for
visual positional awareness.  Now that the SFS boys have proven that it can
do the same thing for that third dimension, it's up to us I think to
encourage the FAA to certify the SFS system for precision IFR work and make
the EFIS 2000 technology the standard for the future of precision
approaches.  As I said before, it's already here, and it can be relatively
inexpensive when the units are mass-produced.

I'm sure you'll be ecstatic with your EFIS 2000 panel, not just for
convenience but for added capability and safety.

I have no connection whatsoever with Sierra Flight Systems except that I am
one of their first customers and can easily see that this system is WAY out
ahead of the pack.
Regards......John Barrett, CARBINGE

-----Original Message-----
From: Jack Hickham [mailto:hickham@webtv.net]
Sent: Monday, May 14, 2001 5:23 PM
To: John Barrett
Subject: Re: List #34"Wazzup with WAAS?

John,
It seems to me if you could count on the altimeter or GPS as being
accurate for altitude you would not even need the ILS or a SFS since the
approach plates gives an accurate threshhold height.
SNIP 
Regards,   JACK


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