From: Bob Noel
Subject: Re: GPS and IFR Approache
Organization: The MITRE Corporation
Date: Thu, 17 Dec 1992 20:04:01 GMT

In article <1992Dec17.163931.17281@mintaka.lcs.mit.edu>
mikec@ginger.lcs.mit.edu (Mike Ciholas) writes:
>
>>what "MLS fiasco"???
>
>Costs too much, does too little.  I believe the US airlines recently
>did an about face on MLS and are no longer pushing for it.  Now that
>the US has sucessfully got the ICAO to endorse MLS there is no turning
>back.  Some airports in the US will have MLS.  As a backup for the big
>jets, its probably a good thing since it is arguably better than ILS
>in performance.  But it will never be a GA thing.  DGPS can and will
>be (and the big jets will like it too).

1.  The US airlines were never real big on MLS.

2.  The US wasn't and isn't the lead on MLS in ICAO.

3.  Some airports will have MLS -- yep, the airports have to have MLS
    because of international commitments.  MLS will be the
    precision approach system for international runways.  (runways
    serving international flight)

4.  MLS is so much better than ILS the comparison is ridiculous.  

5.  "But it will never be a GA thing"  we'll see.  MLS exists
    GPS (or DGPS) is unproven and require significant work with
    respect to availability and integrity.  If it (GPS) works for
    precision approaches, great.  But, we need a precision approach
    system that works when the FM frequency protection dies in '97.
    ILS already has problems in Europe due to FM interference.

    (Maybe us pilots should be working to protect our approach
     systems for FM interference)
    

Re cost:

What cost figures are you looking at?  site preparations for the MLS
ground systems are significantly less than ILS.  The receiver costs will
be a wash (MLS or GPS).  The real costs for the receivers will be in flying
fancy curved (or segmented) approaches.  DGPS will require a ground site.

Also, do you realize what it costs to build a GPS satellite, place
the payload into the correct orbit, maintain the ground control system, 
and production line (assuming you want to replace sick payloads)?

btw, these GPS receivers for sale today ain't going to be the
receivers that will be able to handle GPS (or DGPS) precision approaches.
So, let's not make the mistake of saying "gee, I can buy a GPS
receiver today for <$1000.00, a GPS receiver for IFR
precision approaches won't cost much more"


>
>>From what I've seen regarding LORAN accuracy (i.e., seasonal variation),
>>I'm glad the FAA didn't go charging off and implement LORAN approaches.
>
>Unfortunately, they sorta did.  Of course, they are all NOTAM'ed out
>of service.  I wish they hadn't set them up because the experience the
>FAA and pilots (if any at all) will get will be detrimental to the
>adoption of GPS non-precision approaches and later DGPS precision
>approaches.  Guilty by association, you see.  Here is one area where
>the pushing of AOPA has not served us well, IMHO.  They are doing some
>interesting work on GPS and DGPS that seems more technical and less
>political.  It is better to win on technical grounds than political.
>
>There is a wide spread unconscious notion that area navigation is the
>same, be it Loran or GPS.  NO, NO, NO!  The underlying technology of
>GPS and Loran are vastly different.  Just because the displays look
>the same doesn't mean the quality of information is the same.

I'm certainly not confusing LORAN and GPS.  Believe me, I know the
differences between LORAN, GPS, DGPS _and_ MLS and ILS (and the
strengths and weaknesses of these systems)


Newsgroups: rec.aviation.ifr