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GPS Question



 
 
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  #11  
Old March 10th 06, 03:02 AM posted to rec.aviation.ifr
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Default GPS Question


"kgruber" wrote in message
...
Except for flying an approach at the alternate:

Ref: AIM 1-1-19, paragraph f.1.(b)(8)
Restrictions

"For TSO-C129/129A users, any required alternate airport must still have
an approved instrument approach procedure other than GPS that is
anticipated to be operational and available at the estimated time of
arrival, and which the aircraft is equipped to fly. If the non-GPS
approaches on which the pilot must rely require DME or ADF, the aircraft
must be equipped with DME or ADF avionics as appropriate."


Not so. One can still fly a GPS approach at the alternate. You just need
the other equipment installed. If you have approved WAAS avionics, you may
plan to use any instrument approach authorized for use with WAAS avionics
at a required alternate.

Karl
"Curator" N185KG


"Not so" on which point?

The AIM clearly states that the FILED alternate must "still have an approved
instrument approach procedure other than GPS..." That's word for word out
of the book. But it doesn't SAY you can't FLY a GPS approach at said
alternate, so I agree that you can fly a GPS approach at your filed
alternate. It just can't be the ONLY approach available at that alternate.

There are several airports around that have only a GPS approach or only
approaches (such as an ILS or VOR) that require DME or NDB for position
fixing and/or executing the missed. These airports are, therefore, not
LEGAL alternates for the purpose of filing an alternate. The motivation
here is to have an executable Plan B in case of RAIM failure or GPS
interference or jamming. If GPS keeps humming, no harm, no foul but if it
lets you down for any reason, you'll need the *real* DME or ADF installed to
navigate the approach and that's the point of the AIM reference.

I also agree with your second point about WAAS equipment but your point is
outside the scope of the AIM paragraph in that it addresses TSO-C129/129A
installations, not TSO-145A which applies to WAAS augmentation of GPS.

Therefore, if your new Cirrus doesn't have bona fide NDB, DME, or WAAS, your
FILED alternate would need to have an available approach without the
requirement for any of those.

That being said, what you file and what you fly will likely be based on why
you miss the primary approach in the first place.



  #12  
Old March 10th 06, 03:06 AM posted to rec.aviation.ifr
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Default GPS Question

unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).


Except, of course, for the famous VOR/DME OR TACAN Z RWY 15 approach at
Martin State:

http://www.naco.faa.gov/d-tpp/0602/05222VDTZ15.PDF

Are you saying that you can't use the GPS in lieu of DME for that approach?
Why not?


Yes, because the DME is the "principal instrument approach navigation
source" - that approach is a DME arc to the runway.



  #13  
Old March 10th 06, 03:10 AM posted to rec.aviation.ifr
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Default GPS Question


"Barry" wrote in message
. ..
unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).

Except, of course, for the famous VOR/DME OR TACAN Z RWY 15 approach at
Martin State:

http://www.naco.faa.gov/d-tpp/0602/05222VDTZ15.PDF

Are you saying that you can't use the GPS in lieu of DME for that
approach?
Why not?


Yes, because the DME is the "principal instrument approach navigation
source" - that approach is a DME arc to the runway.



A subtle but important observation! Have you won any bets with that one?


  #14  
Old March 10th 06, 03:37 AM posted to rec.aviation.ifr
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Default GPS Question

It just can't be the ONLY approach available at that alternate.

Actually, it can... just not at the time of filing. If your alternate
has another approach (say an ILS), making it legal for filing as an
alternate, and when things go south, their ILS also dies, you can still
legally FLY their GPS approach, or an approach requring NDB or DME
(except an NDB approach). To fly their NDB approach you'd need the
emergency authority.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.
  #15  
Old March 10th 06, 04:03 AM posted to rec.aviation.ifr
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Default GPS Question

In article ,
Jose wrote:

It just can't be the ONLY approach available at that alternate.


Actually, it can... just not at the time of filing. If your alternate
has another approach (say an ILS), making it legal for filing as an
alternate, and when things go south, their ILS also dies, you can still
legally FLY their GPS approach, or an approach requring NDB or DME
(except an NDB approach). To fly their NDB approach you'd need the
emergency authority.


Emergency authority? Let me understand this, you couldn't get into your
destination, bugged out to your alternate, discovered that the ILS there
went TU, and you're still worrying about what some lawyer thinks?
  #16  
Old March 10th 06, 04:27 AM posted to rec.aviation.ifr
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Default GPS Question

Emergency authority? Let me understand this, you couldn't get into your
destination, bugged out to your alternate, discovered that the ILS there
went TU, and you're still worrying about what some lawyer thinks?


No, I'm not worried. But the lawyer is still thinking. And since the
thread is about legality, not practicality, I'm thinking too.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.
  #17  
Old March 10th 06, 12:51 PM posted to rec.aviation.ifr
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Default GPS Question

On Fri, 10 Mar 2006 02:10:56 GMT, "Dan Wegman"
wrote:


"Barry" wrote in message
...
unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).

Except, of course, for the famous VOR/DME OR TACAN Z RWY 15 approach at
Martin State:

http://www.naco.faa.gov/d-tpp/0602/05222VDTZ15.PDF
Are you saying that you can't use the GPS in lieu of DME for that
approach?
Why not?


Yes, because the DME is the "principal instrument approach navigation
source" - that approach is a DME arc to the runway.



A subtle but important observation! Have you won any bets with that one?


Might I ask what makes that approach any different than the ILS/DME
RWY 2 approach APOA uses as the sample in their "Use of GPS in lieu"
piece (
http://www.aopa.org/whatsnew/air_tra...u.html#figurea )
where they say "DME arcs associated with instrument approaches may be
flown using GPS distance provided the DME transmitter, on which the
arc is based, is identified in the GPS database (see Figure A)." ?

Course if we're talking about determining an alternate while planning
than yea, no substitution - but if the station is in the database and
you're shooting the approach it seems to fit the substitution rules to
me?
  #18  
Old March 10th 06, 04:24 PM posted to rec.aviation.ifr
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Default GPS Question

On 03/09/06 18:06, Barry wrote:
unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).

Except, of course, for the famous VOR/DME OR TACAN Z RWY 15 approach at
Martin State:

http://www.naco.faa.gov/d-tpp/0602/05222VDTZ15.PDF

Are you saying that you can't use the GPS in lieu of DME for that approach?
Why not?


Yes, because the DME is the "principal instrument approach navigation
source" - that approach is a DME arc to the runway.


Oh, right! I've never seen that before. Very cool looking approach.

I knew I was going to learn something new today :-)

Thanks for pointing it out.

Best Regards,

--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA
  #19  
Old March 10th 06, 05:48 PM posted to rec.aviation.ifr
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Default GPS Question

On Fri, 10 Mar 2006 12:11:24 GMT, "Steven P. McNicoll"
wrote:


"Peter Clark" wrote in message
.. .

Might I ask what makes that approach any different than the ILS/DME
RWY 2 approach APOA uses as the sample in their "Use of GPS in lieu"
piece (
http://www.aopa.org/whatsnew/air_tra...u.html#figurea )
where they say "DME arcs associated with instrument approaches may be
flown using GPS distance provided the DME transmitter, on which the
arc is based, is identified in the GPS database (see Figure A)." ?


The ILS/DME RWY 2 at DRO uses a localizer for the principal instrument
approach navigation source. The VOR/DME or TACAN Z RWY 15 at MTN uses DME
as the principal instrument approach navigation source.


Um, OK, I'm thick. I don't get what substitution rule I'm still
missing? With either approach you're using the VOR head for lateral
guidance and reading the distance from some fix in the GPS database
from the GPS head. Even the example approach used for how to do a DME
ARC in the KLN 94 GPS manual is an VOR/DME approach using an arc.
  #20  
Old March 10th 06, 06:03 PM posted to rec.aviation.ifr
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Posts: n/a
Default GPS Question


"Peter Clark" wrote in message
...

Um, OK, I'm thick. I don't get what substitution rule I'm still
missing? With either approach you're using the VOR head for lateral
guidance and reading the distance from some fix in the GPS database
from the GPS head. Even the example approach used for how to do a DME
ARC in the KLN 94 GPS manual is an VOR/DME approach using an arc.


But you're not using the VOR head for lateral guidance and reading the
distance from some fix in the GPS database from the GPS head with either
approach. The VOR/DME or TACAN Z RWY 15 at MTN would have you using DME
for lateral guidance and determining your position on the final approach
course from crossing VOR radials. If you substituted GPS for DME on that
approach you'd be substituting for DME where it was the principal instrument
approach navigation source.


 




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