Tim(at)MyRV10.com
Guest
|
 Posted: Sun Jun 11, 2006 6:17 am Post subject: Experimental IFR w/o a certified GPS or looking for a copy |
 |
|
Great explanation, Kevin. To me, the one that really throws out most
GPS's that we'd consider is the integrity monitoring, which just
isn't there on many (most) units that aren't certified. And the
update rates for WAAS approach units. There's a reason that only
2 models of GPS (Freeflight and GNS480) are currently certified for
WAAS approaches, and that's because they're the only ones currently
meeting the requirement. If others really met the requirement, but
weren't tested, I'm sure the companies would be testing them because
they'd be big sellers. It's why I have a GNS480 in my panel, but
personally, I'd have been better off with a freeflight in my
situation. I may add one someday.
Tim Olson - RV-10 N104CD - Flying
do not archive
Kevin Horton wrote:
| Quote: |
<khorton01(at)rogers.com>
On 11 Jun 2006, at 02:22, Deems Davis wrote:
>
>
> I recently read an article posted on Direct2. website
> http://www.direct2avionics.com/pdfs/Using_GPS_for_IFR_flight.pd by a
> Phd CFII that concludes that for EXPERIMENTAL aircraft, it was not
> necessary for the aircraft to be equipped with a CERTIFIED GPS
> receiver to legally file and fly IFR, PROVIDED that you, the pilot/mfg
> can evaluate the GPS functionality, and find it provides all of the
> necessary pilot input (as defined in the TSO) for IFR flight.
>
> This sounded like it was worth looking into. I verified this opinion
> with a competitor of Direct2. So off I go to study TSO-C146 the
> Standard document for WAAS GPS, unfortunately there is nothing in the
> document regarding functional requirements other than a reference to:
> RTCA/DO-229B (which I learned has since been superceeded w/
> RTCA/DO-229C). Another Google search reveals that this document is
> available but with a cost which ranged from $108-370 per copy.
> Does anyone know of a 'library' where this document could be 'rented'
> or checked-out. a couple hundred bucks is a steep price for someone
> just investigating an idea/thought.
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
http://www.matronics.com/Navigator?AeroElectric-List
http://wiki.matronics.com
|
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
