Return-Path: Received: from pop3.olsusa.com ([63.150.212.2] verified) by logan.com (CommuniGate Pro SMTP 3.4.5) with ESMTP id 780238 for rob@logan.com; Tue, 15 May 2001 10:32:13 -0400 Received: from olympus.net ([198.133.237.6]) by pop3.olsusa.com (Post.Office MTA v3.5.3 release 223 ID# 0-71175U5500L550S0V35) with ESMTP id com for ; Tue, 15 May 2001 09:39:44 -0400 Received: from pt195193.olympus.net ([207.149.195.193] helo=pavilion) by olympus.net with smtp (Exim 3.12 #1) id 14zf9s-000255-00; Tue, 15 May 2001 06:46:40 -0700 From: "John Barrett" <2thman@olympus.net> To: "Jack Hickham" , "Lancair Mail List" Cc: "Gordon Pratt" Subject: RE: List #34"Wazzup with WAAS? Date: Tue, 15 May 2001 06:41:42 -0700 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Importance: Normal In-Reply-To: <3561-3B0076F5-3612@storefull-138.iap.bryant.webtv.net> X-Mailing-List: lancair.list@olsusa.com Reply-To: lancair.list@olsusa.com <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> 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 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML website: http://www.olsusa.com/Users/Mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>