GPS Question

[rps]

I thought I understood this, but maybe not. GPS systems were certified
for approaches after I got my instrument ticket, so my knowledge is
more anecdotal than from actual training.

Can an approach-certified GPS be used to substitute for NDB and DME
during an approach (or even en route)? What if the approach says ADF
Required or DME Required? My understanding of the AIM is that you can
only use the GPS as a substitute when there is a published GPS overlay
for the approach.

(My question is about the legality and not about whether you'd be close
enough.)

[Mark Hansen]

On 03/09/06 11:35, rps wrote:
> I thought I understood this, but maybe not. GPS systems were certified
> for approaches after I got my instrument ticket, so my knowledge is
> more anecdotal than from actual training.
>
> Can an approach-certified GPS be used to substitute for NDB and DME
> during an approach (or even en route)? What if the approach says ADF
> Required or DME Required? My understanding of the AIM is that you can
> only use the GPS as a substitute when there is a published GPS overlay
> for the approach.
>
> (My question is about the legality and not about whether you'd be close
> enough.)
>

The AIM has a section devoted to the use of GPS in lieu of ADF and DME,
which will answer your question, and much more ;-)

Go to section 1-1-19, and look for "Use of GPS in lieu of ADF and DME".

The short answer is yes, you can use GPS as a replacement for ADF and DME
unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).

So, if you're flying an NDB approach, you could not use the GPS as a
replacement for the NDB ground station.

However, if you're flying an approach that requires DME, or an NDB to
identify the OM, you can use the GPS to provide that information.


--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

[Jose]

> Can an approach-certified GPS be used to substitute for NDB and DME
> during an approach (or even en route)? What if the approach says ADF
> Required or DME Required? My understanding of the AIM is that you can
> only use the GPS as a substitute when there is a published GPS overlay
> for the approach.

My understanding is that it can, except for an NDB approach. If the NDB
approach has a GPS overlay, then it is a GPS approach anyway.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

[Peter R.]

Mark Hansen > wrote:

> So, if you're flying an NDB approach, you could not use the GPS as a
> replacement for the NDB ground station.

Here in the lower 48 states, the NDB approach is fast going the way of the
Dodo bird. Every Jepp update I have received over the last 6 months seems
to require the removal of more NBD approaches than those I replace.

--
Peter

[Barry]

> 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

[Mark Hansen]

On 03/09/06 12:51, 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?

--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

[Dan Wegman]

"Mark Hansen" > wrote in message
...
> On 03/09/06 11:35, rps wrote:
>> I thought I understood this, but maybe not. GPS systems were certified
>> for approaches after I got my instrument ticket, so my knowledge is
>> more anecdotal than from actual training.
>>
>> Can an approach-certified GPS be used to substitute for NDB and DME
>> during an approach (or even en route)? What if the approach says ADF
>> Required or DME Required? My understanding of the AIM is that you can
>> only use the GPS as a substitute when there is a published GPS overlay
>> for the approach.
>>
>> (My question is about the legality and not about whether you'd be close
>> enough.)
>>
>
> The AIM has a section devoted to the use of GPS in lieu of ADF and DME,
> which will answer your question, and much more ;-)
>
> Go to section 1-1-19, and look for "Use of GPS in lieu of ADF and DME".
>
> The short answer is yes, you can use GPS as a replacement for ADF and DME
> unless the navigational station is the primary for the approach (which
> could be true for ADF, but not DME).
>
> So, if you're flying an NDB approach, you could not use the GPS as a
> replacement for the NDB ground station.
>
> However, if you're flying an approach that requires DME, or an NDB to
> identify the OM, you can use the GPS to provide that information.
>
>
> --
> Mark Hansen, PP-ASEL, Instrument Airplane
> Cal Aggie Flying Farmers
> Sacramento, CA

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."

[Michael R]

They've gotten rid of a bunch of NDB approaches, but there were still 1,283
left as of 10/27/05.



"Peter R." > wrote in message
...
> Mark Hansen > wrote:
>
>> So, if you're flying an NDB approach, you could not use the GPS as a
>> replacement for the NDB ground station.
>
> Here in the lower 48 states, the NDB approach is fast going the way of the
> Dodo bird. Every Jepp update I have received over the last 6 months seems
> to require the removal of more NBD approaches than those I replace.
>
> --
> Peter

[Jose]

> Except for flying an approach at the alternate:

Nope. Except for determining a legal alternate. Once you are in the
air, if you need to go to =an= alternate, it doesn't have to be your
filed one, and even if you decide to go to your filed alternate, there
are no special GPS rules. You can use the approach-certified GPS as a
substitute for NDB and DME, except for an NDB approach, just like your
original destination.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

[kgruber]

> 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

[Dan Wegman]

"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.

[Barry]

>>> 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.

[Dan Wegman]

"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?

[Jose]

> 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.

[Roy Smith]

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?

[Jose]

> 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.

[Peter Clark]

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_traffic/gps_in_lieu.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?

[Mark Hansen]

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

[Peter Clark]

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_traffic/gps_in_lieu.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.

[Steven P. McNicoll]

"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.

[Jose]

> 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.

I guess the idea is that your position "on track" and "along track" need
differing amounts of, for lack of a better word, attention. You are
pointed along track and will cover all the along-track positions. You
want to remain on track, and not left or right of track.

For a regular VOR approach, it is the VOR that keeps you on track. DME
just reports your "along track" progress. For a DME arc it's the
reverse. You stay "on track" referring to the DME, and the VOR just
reports your "along track" progress.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

[rps]

This article refers to the LDA/DME RWY 23 approach at EKO in Figure B.
I tried "flying" that approach on the Garmin 430 simulator and blew it
the first time because I was watching the distance readout on the
Garmin primary nav page (1st Nav page). I forgot that the unit
indicates distance to the next waypoint. After crossing the FAF, the
distance field on the nav page indicates the GPS distance to the next
waypoint (missed approach point here) rather than distance from the FAF
or the DME reference point.

What probably threw me off was that the AOPA article cautions readers
that while DME units will count DOWN to the missed approach point
(because the path is towards the DME reference point), GPS units will
count UP from the FAF. In contrast, the 430 counts DOWN to the next
waypoint (the missed approach point here). To count up from the FAF,
I'd probably have to hit OBS when approaching the FAF (though didn't
try it).

What procedure would other users of Garmin 430/530 units use with this
approach? Ideally, I'd want to see either the primary nav page or the
map page with distance shown from the DME reference point (so that I
don't have to do math in my head during the approach to calculate
distance from the FAF).

[Peter Clark]

On Fri, 10 Mar 2006 17:03:16 GMT, "Steven P. McNicoll"
> wrote:

>
>"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.

OK, I'm not trying to be obtuse here, I'd really like to understand
what I'm doing wrong. I'm flying along using the GPS head to tell me
I'm on an arc (X) miles from (Y) transmitter, twisting the VOR head
every 10deg or so until I hit the leadin radial and then turn inbound
(or in the case of the DC approach see the runway or go missed). The
manual documents this scenario. The AOPA article seems to document
the same usage. Yet it's not allowed by the substitution rules?

[Steven P. McNicoll]

"Peter Clark" > wrote in message
...
>
> OK, I'm not trying to be obtuse here, I'd really like to understand
> what I'm doing wrong. I'm flying along using the GPS head to tell me
> I'm on an arc (X) miles from (Y) transmitter, twisting the VOR head
> every 10deg or so until I hit the leadin radial and then turn inbound
> (or in the case of the DC approach see the runway or go missed). The
> manual documents this scenario. The AOPA article seems to document
> the same usage. Yet it's not allowed by the substitution rules?
>

AIM para 1-1-19.f.1.(b)(6):

"Charted requirements for ADF and/or DME can be met using the GPS system,
except for use as the principal instrument approach navigation source.

What serves as the principal instrument approach navigation source for the
ILS/DME RWY 2 at DRO? What serves as the principal instrument approach
navigation source for the VOR/DME RWY 15 at MTN?

[Greg Esres]

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

Sounds like pure speculation to me. Can you support with any FAA
material?

[Peter Clark]

On Sat, 11 Mar 2006 04:12:16 GMT, "Steven P. McNicoll"
> wrote:

>
>"Peter Clark" > wrote in message
...
>>
>> OK, I'm not trying to be obtuse here, I'd really like to understand
>> what I'm doing wrong. I'm flying along using the GPS head to tell me
>> I'm on an arc (X) miles from (Y) transmitter, twisting the VOR head
>> every 10deg or so until I hit the leadin radial and then turn inbound
>> (or in the case of the DC approach see the runway or go missed). The
>> manual documents this scenario. The AOPA article seems to document
>> the same usage. Yet it's not allowed by the substitution rules?
>>
>
>AIM para 1-1-19.f.1.(b)(6):
>
>"Charted requirements for ADF and/or DME can be met using the GPS system,
>except for use as the principal instrument approach navigation source.
>
>What serves as the principal instrument approach navigation source for the
>ILS/DME RWY 2 at DRO? What serves as the principal instrument approach
>navigation source for the VOR/DME RWY 15 at MTN?

OK, using that as a baseline then GPS wouldn't be a permissible
substitute for DME in any approach using a DME arc, so why would it be
documented in the manuals if it's not permissible?

[Steven P. McNicoll]

"Peter Clark" > wrote in message
...
>>
>>AIM para 1-1-19.f.1.(b)(6):
>>
>>"Charted requirements for ADF and/or DME can be met using the GPS system,
>>except for use as the principal instrument approach navigation source.
>>
>>What serves as the principal instrument approach navigation source for the
>>ILS/DME RWY 2 at DRO? What serves as the principal instrument approach
>>navigation source for the VOR/DME RWY 15 at MTN?
>>
>
> OK, using that as a baseline then GPS wouldn't be a permissible
> substitute for DME in any approach using a DME arc, so why would it be
> documented in the manuals if it's not permissible?
>

You didn't answer the questions. We can proceed only after you answer the
questions.

[Sam Spade]

Greg Esres wrote:

>
> Sounds like pure speculation to me. Can you support with any FAA
> material?

Doesn't seem speculative to me. The FAA material is the fact that the
final approach couse is a DME ARC printed on the approach chart in bold
type. A good understanding of approach chart symbology would make that
apparent.

Also, there are the TERPS:

523. FINAL APPROACH SEGMENT. TACAN and VOR/DME final approaches may be
based either on arcs or radials. The final approach begins at a FAF and
ends at the MAP. The MAP is always marked with a fix.
a. Radial Final Approach. Criteria for the radial final approach are
specified in paragraph 513.
b. Arc Final Approach. The final approach arc shall be a continuation of
the intermediate arc. It shall be specified in NM and tenths thereof.
Arcs closer than 7 miles (15 miles for high altitude procedures) and
farther than 30 miles from the facility shall NOT be used for final
approach. No turns are permitted over the FAF.
(1) Alignment. For straight-in approaches, the final approach arc shall
pass through the runway threshold when the angle of convergence of the
runway centerline and the tangent of the arc does not exceed 15 degrees.
When the angle exceeds 15 degrees the final approach arc shall be
aligned to pass through the center of the airport and only circling
minimums shall be authorized. See Figure

[Peter Clark]

On Sat, 11 Mar 2006 20:17:46 GMT, "Steven P. McNicoll"
> wrote:

>
>"Peter Clark" > wrote in message
...
>>>
>>>AIM para 1-1-19.f.1.(b)(6):
>>>
>>>"Charted requirements for ADF and/or DME can be met using the GPS system,
>>>except for use as the principal instrument approach navigation source.
>>>
>>>What serves as the principal instrument approach navigation source for the
>>>ILS/DME RWY 2 at DRO? What serves as the principal instrument approach
>>>navigation source for the VOR/DME RWY 15 at MTN?
>>>
>>
>> OK, using that as a baseline then GPS wouldn't be a permissible
>> substitute for DME in any approach using a DME arc, so why would it be
>> documented in the manuals if it's not permissible?
>>
>
>You didn't answer the questions. We can proceed only after you answer the
>questions.

OK. I believe the answer is the GS/localizer and VOR respectively.

[Steven P. McNicoll]

"Peter Clark" > wrote in message
...
>
> OK. I believe the answer is the GS/localizer and VOR respectively.
>

Why did you choose VOR for the VOR/DME RWY 15 at MTN? Do you see VOR
serving the same role there as the localizer does for the ILS/DME RWY 2 at
DRO?

[Peter Clark]

On Sun, 12 Mar 2006 03:21:06 GMT, "Steven P. McNicoll"
> wrote:

>
>"Peter Clark" > wrote in message
...
>>
>> OK. I believe the answer is the GS/localizer and VOR respectively.
>>
>
>Why did you choose VOR for the VOR/DME RWY 15 at MTN? Do you see VOR
>serving the same role there as the localizer does for the ILS/DME RWY 2 at
>DRO?

I chose it because it's the point where the rest of the required
information (distance to maintain from and radial crossing) is derived
from.

For the arc portion of the DRO approach, no - the DRO VOR serves the
same purpose for that approach until hitting the lead radial.

[Roger]

On Sun, 12 Mar 2006 19:19:10 +0000, Peter >
wrote:

>Sorry if this is a dumb question but a quick look at that Baltimore
>approach looks like the DME arc is the sole lateral guidance
>mechanism.
>
>I can fly DME arcs fine but have done them only as earlier parts of
>approaches.
>
>How easy is it to fly a DME arc to the required degree of accuracy?

It's been a while (like 4 or 5 years) since I had to do one but found
then relatively easy. Just remember which way to turn and watch the
DME.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>There is no left/right indication anywhere; you are turning left/right
>according to the digital DME readout.
>
>I notice the MDH is quite generous on this one; perhaps that's the
>reason...

[Steven P. McNicoll]

"Peter Clark" > wrote in message
...
>
> I chose it because it's the point where the rest of the required
> information (distance to maintain from and radial crossing) is derived
> from.
>

The I-DRO localizer provides distance information?


>
> For the arc portion of the DRO approach, no - the DRO VOR serves the
> same purpose for that approach until hitting the lead radial.
>

What navaid provides lateral guidance on the final approach course at DRO?
What navaid provides lateral guidance on the final approach course at MTN?


Here's a link to an approach at Antigo, Wisconsin:

http://www.myairplane.com/databases/approach/pdfs/06215N16.PDF

Can GPS substitute for ADF on this approach? Please explain your answer.

[Steven P. McNicoll]

"rps" > wrote in message
oups.com...
>
> My answer, based on what I learned from this thread and by reading
> elsewhere, is that you cannot substitute GPS for ADF on this approach
> because:
>
> 1) The chart doesn't indicate an overlay approach, such as with the
> nomenclature "NDB/GPS" in the title; and
> 2) the NDB is the "primary" signal source for the approach. (See the
> relevant AIM sections.)
>

Right, GPS cannot substitute for ADF on this approach because ADF is the
principal instrument approach navigation source. For that same reason GPS
cannot substitute for DME on the VOR/DME or TACAN Z RWY 15 at MTN.

[Peter Clark]

On Mon, 13 Mar 2006 22:54:03 GMT, "Steven P. McNicoll"
> wrote:

>
>"Peter Clark" > wrote in message
...
>>
>> I chose it because it's the point where the rest of the required
>> information (distance to maintain from and radial crossing) is derived
>> from.
>>
>
>The I-DRO localizer provides distance information?

Who knows, the arc is based off the VOR/DME transmitter. I believe I
corrected that oversight in a later response.

>> For the arc portion of the DRO approach, no - the DRO VOR serves the
>> same purpose for that approach until hitting the lead radial.
>>
>
>What navaid provides lateral guidance on the final approach course at DRO?
>What navaid provides lateral guidance on the final approach course at MTN?

None. Distance is from the VOR/DME transmitters, or in the case of an
ILS/DME the I-<whatever>. For these approaches I'm substituting the
GPS distance readout instead of having an actual DME box and using the
VOR head to drive the CDI for cross radials. Flying a DME arc is
specifically listed as a permitted operation in the AIM
1-1-19(f)(1)(a)(2).

>Here's a link to an approach at Antigo, Wisconsin:
>
>http://www.myairplane.com/databases/approach/pdfs/06215N16.PDF
>
>Can GPS substitute for ADF on this approach? Please explain your answer.

No, because there's no GPS overlay.

[Jose]

> Who knows, the arc is based off the VOR/DME transmitter.

VOR and DME are two separate transmitters, on two separate frequencies,
with two separate methods. The channels are coordinated, that's about
all they have in common (except location at a co-located VOR/DME)

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

[Peter Clark]

On Tue, 14 Mar 2006 00:05:04 GMT, "Steven P. McNicoll"
> wrote:

>
>"rps" > wrote in message
oups.com...
>>
>> My answer, based on what I learned from this thread and by reading
>> elsewhere, is that you cannot substitute GPS for ADF on this approach
>> because:
>>
>> 1) The chart doesn't indicate an overlay approach, such as with the
>> nomenclature "NDB/GPS" in the title; and
>> 2) the NDB is the "primary" signal source for the approach. (See the
>> relevant AIM sections.)
>>
>
>Right, GPS cannot substitute for ADF on this approach because ADF is the
>principal instrument approach navigation source. For that same reason GPS
>cannot substitute for DME on the VOR/DME or TACAN Z RWY 15 at MTN.

But if you can't substitute DME to fly an arc because it's the primary
source of navigation then why is "DME arc" specifically listed in AIM
1-1-19 (f)(1)(a)(2) and <blah>/DME with arcs used as the examples of
permissible substitution on the AOPA GPS substitution page? That's
the piece of the puzzle I'm missing here.

[Steven P. McNicoll]

"Peter Clark" > wrote in message
...
>
> Who knows, the arc is based off the VOR/DME transmitter. I believe I
> corrected that oversight in a later response.
>

Who knows? Everybody that understands the applicable publications.


>
> None. Distance is from the VOR/DME transmitters, or in the case of an
> ILS/DME the I-<whatever>. For these approaches I'm substituting the
> GPS distance readout instead of having an actual DME box and using the
> VOR head to drive the CDI for cross radials. Flying a DME arc is
> specifically listed as a permitted operation in the AIM
> 1-1-19(f)(1)(a)(2).
>

Right. No navaid provides lateral guidance on the final approach course for
either of these IAPs. Why would lateral guidance be needed on an instrument
approach anyway?

It appears you were fibbin' when you said you weren't trying to be obtuse
here.


>
> No, because there's no GPS overlay.
>

Right answer, wrong reason.

[Mark Hansen]

On 03/14/06 08:51, Peter wrote:
> "Steven P. McNicoll" > wrote:
>
>>Right, GPS cannot substitute for ADF on this approach because ADF is the
>>principal instrument approach navigation source. For that same reason GPS
>>cannot substitute for DME on the VOR/DME or TACAN Z RWY 15 at MTN.
>
> I am from Europe, where US-style GPS substitution for various navaids
> is not permitted. So this is of academic interest only.
>
> (With one small exception I know of, Switzerland, where (as is not
> uncommon in Europe) an ADF is required for all controlled airspace
> unless one carries a BRNAV approved GPS.)
>
> Anyway, this thread has left me well confused. I've done the FAA IR
> (at a U.S. school not using GPS so GPS questions didn't come up) so I
> recall that any navaid shown on the approach plate can be substituted
> for the OM, and only radar or an NDB (a "compass locator") can subst
> for the middle marker.
>
> I also recall that if an alternate is required (the destination not
> meeting the 1/2/3 rule)

.... or if the destination doesn't have an instrument approach

> and the only approach available at the
> alternate is a GPS one, that airport cannot be filed as an
> alternate.... or something like that. This requirement (which I
> probably wrote wrongly) is what puzzles me regarding Cirrus (for
> example) not being fitted with an ADF and a DME - doesn't it curtail
> the alternate options considerably?

Not at all. There are a lot of ILS, VOR, etc. approaches which do not
require DME or ADF. Note that you do not need an ADF to make use of
the OM and MM - a marker beacon receiver is just fine.

>
> Getting back to the more general substitution regs: on the *primary*
> destination, is it OK to substitute a GPS for any navaid provided the
> navaid is not used to provide the lateral guidance?

There is a section in the AIM which covers this question exactly. It
is called "Use of GPS in lieu of ADF and DME".

In this case, we're not talking about GPS approaches, but approaches
like ILS, VOR, NDB, etc. In these cases, the GPS can be used as a
substitute for the ADF and/or DME (in specific cases, as detailed
by the AIM). However, you would not be able to substitute the VOR
on a VOR approach, etc. For that, you need to fly the VOR (GPS)
or GPS approach.


--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

[[email protected]]

Steven P. McNicoll > wrote:

> Here's a link to an approach at Antigo, Wisconsin:

WOW! My home town! :-) However, I learned to fly at Cheyenne, WY.

> http://www.myairplane.com/databases/approach/pdfs/06215N16.PDF

> Can GPS substitute for ADF on this approach? Please explain your answer.

No. The ADF is the Primary navaid. To use the GPS for this
approach, the approach would be relabeled, using "GPS" in the
header.

--------------------------------------------------------------------

Now, please review with me my home airport... KFNL
http://www.myairplane.com/databases/approach/pdfs/05677I33.PDF

Note in the lower left of the central graphic box, where it says
"ADF REQUIRED". In this case the GPS may be substituted for the
NDB, as this is an ILS approach and the NDB is not the primary
navaid.

Best regards,

Jer/ "Flight instruction and mountain flying are my vocations!"
--
Jer/ (Slash) Eberhard, Mountain Flying Aviation, LTD, Ft Collins, CO
CELL 970 231-6325 EMAIL jer<at>frii.com http://users.frii.com/jer/
C-206 N9513G, CFII Airplane&Glider FAA-DEN Aviation Safety Counselor
CAP-CO Mission&Aircraft CheckPilot BM218 HAM N0FZD 240 Young Eagles!

[Steven P. McNicoll]

> wrote in message ...
>
> WOW! My home town! :-) However, I learned to fly at Cheyenne, WY.
>

When did you live in Antigo?


>
> No. The ADF is the Primary navaid. To use the GPS for this
> approach, the approach would be relabeled, using "GPS" in the
> header.
>

Correct.


>
> Now, please review with me my home airport... KFNL
> http://www.myairplane.com/databases/approach/pdfs/05677I33.PDF
>
> Note in the lower left of the central graphic box, where it says
> "ADF REQUIRED". In this case the GPS may be substituted for the
> NDB, as this is an ILS approach and the NDB is not the primary
> navaid.
>

Correct, ADF is needed for the missed approach procedure.

[rps]

Steven P. McNicoll wrote:
> > wrote in message ...
> >
> >> > Now, please review with me my home airport... KFNL
> > http://www.myairplane.com/databases/approach/pdfs/05677I33.PDF
> >
> > Note in the lower left of the central graphic box, where it says
> > "ADF REQUIRED". In this case the GPS may be substituted for the
> > NDB, as this is an ILS approach and the NDB is not the primary
> > navaid.
> >
>
> Correct, ADF is needed for the missed approach procedure.

I (the person who started this thread) am confused again. Do I need an
ADF when I shoot this procedure, or not?

Some plates say "ADF Required." I think I've seen some plates say "DME
Required." Can I legally begin the approach in a Cirrus that has no
ADF or DME?

[Dan Wegman]

"rps" > wrote in message
ups.com...
> Steven P. McNicoll wrote:
>> > wrote in message
>> ...
>> >
>> >> > Now, please review with me my home airport... KFNL
>> > http://www.myairplane.com/databases/approach/pdfs/05677I33.PDF
>> >
>> > Note in the lower left of the central graphic box, where it says
>> > "ADF REQUIRED". In this case the GPS may be substituted for the
>> > NDB, as this is an ILS approach and the NDB is not the primary
>> > navaid.
>> >
>>
>> Correct, ADF is needed for the missed approach procedure.
>
> I (the person who started this thread) am confused again. Do I need an
> ADF when I shoot this procedure, or not?
>
> Some plates say "ADF Required." I think I've seen some plates say "DME
> Required." Can I legally begin the approach in a Cirrus that has no
> ADF or DME?
>

Yes, since the primary approach guidance is from the ILS and the NDB is
there to identify the marker and the missed approach holding fix. This is
an example of when the GPS can be used in lieu of the ADF at your
destination airport. But if GPS goes south during the approach and you have
to go missed...

The rule about when you can't use GPS in lieu of DME/ADF applies if you're
required to file an alternate. There must be another approach available at
the alternate that doesn't have a DME/ADF requirement. As I posted earlier,
this is to ensure you have a usable approach in the event of GPS failure.
For this ILS at FNL, you'd probably need radar vectors to guide you to the
marker if you had no GPS and no ADF. But what if you lost comm? Most of
the belt & suspenders safety rules for IFR ops are to give you an 'out' in
the case of lost comm or nav capability. Finding a non-DME or non-ADF
approach could take a bit of searching! But, as a previous poster noted, if
you have to go missed for a non-GPS reason, you can (in my opinion) still
use your GPS in lieu of DME/ADF where you need it. The bottom line is, use
everything you've got to protect your skin, your tin, and your ticket - in
that order.

[Jose]

> But if GPS goes south during the approach and you have
> to go missed...

.... I think the idea is that if you are going missed, you are at a
higher altitude and there is more latitude. If you are on the approach
using the primary navaid for guidance, you are as low as you can go, and
there's much less room for error.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.