BobsV35B(at)aol.com
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 Posted: Sun Jun 11, 2006 4:39 am Post subject: Experimental IFR w/o a certified GPS or looking for a... |
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Good Morning Kevin,
I do not feel at all qualified to evaluate all of the legalities involved, but I tend to agree with your conclusions based on my general knowledge of what the FAA has approved.
One major flaw that I see in the authors interpretation is in his ninth paragraph where he discusses the need for an alternative method of navigation when using TSO C-129 based GPS. He states that there is a requirement that any VOR based checkpoint be operative and viable if that point is used on the flight plan.
That is absolutely NOT true. Any such interpretation he has received is not what the FAA intended the interpretation to be when the 129 set was approved.
He also has wording which could be construed as meaning that the receivers he lists are the only ones approved under that TSO. There are several others that are approved.
With such gross errors in the portions of document with which I am familiar, I find it difficult to place much credence in the rest.
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 6/11/2006 5:40:04 A.M. Central Standard Time, khorton01(at)rogers.com writes:
| Quote: | 1. For anyone else interested in reading the referenced article, the
link is missing the letter "f" at the end. It should be <http://
www.direct2avionics.com/pdfs/Using_GPS_for_IFR_flight.pdf>.
2. The referenced article uses some fuzzy wording. They say the GPS
receiver must provide all "necessary pilot input". What does that
mean? Later on they say that the receiver must provide the required
integrity monitoring. The gist of the article seems to be that the
receiver must meet the requirements of the TSO, which is different
than saying it must be TSO'd. I.e., in theory, you could solder
together your own design GPS receiver, and legally use it, as long as
it had all the functionality and performance required by the TSO.
3. They suggest that you can purchase a non-TSO'd GPS receiver that
meets all the requirements of the TSO, and legally use it. Sounds OK
in theory, but how do you determine whether or not this receiver
meets the TSO requirements? If it really does meet the TSO
requirements, why wouldn't the manufacturer put a TSO data plate on it?
4. I've read TSO C-129 (but not the later TSOs for WAAS receivers).
There is no way you can know whether the system meets the TSO unless
you can dig into the software to look for the required functionality,
and then perform some very difficult tests to see if the
functionality actually works. You would need to provide simulated
GPS signals, with one satellite that had an error, and see if the
system was able to detect it. You would need to measure the
navigation accuracy to very tight tolerances. Etc. The required
testing would probably cost several hundred thousand dollars or more
(cost of required equipment, engineering time, flight test time,
etc). It simply isn't practical for anyone at our level to determine
whether a GPS receiver meets the TSO requirements or not.
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://www.kilohotel.com/rv8
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