Hi all,

a question that has probably been asked before, but I couldn't find it
in Google:

Is it allowed to use an IFR-approach-certified GPS instead of a DME in
a LOC-DME or VOR-DME approach that does not have a GPS-overlay?

Thanks!

--
Thomas Borchert (EDDH)

DME distances will be greater than GPS distances due to slant-range.

Thomas Borchert wrote:
> Hi all,
>
> a question that has probably been asked before, but I couldn't find it
> in Google:
>
> Is it allowed to use an IFR-approach-certified GPS instead of a DME in
> a LOC-DME or VOR-DME approach that does not have a GPS-overlay?
>
> Thanks!
>

Thomas Borchert ) wrote:

> Is it allowed to use an IFR-approach-certified GPS instead of a DME in
> a LOC-DME or VOR-DME approach that does not have a GPS-overlay?

YEs. See AIM 1-1-19. Global Positioning System (GPS), subsection (f).

http://www.faa.gov/ATPubs/AIM/Chap1/aim0101.html#1-1-19

A quote:

--- quote ---

(f) Use of GPS in lieu of ADF and DME

1. Subject to the restrictions below, operators in the U.S. NAS are
authorized to use GPS equipment certified for IFR operations in place of
ADF and/or DME equipment for en route and terminal operations. For some
operations there is no requirement for the aircraft to be equipped with
an ADF or DME receiver, see subparagraphs f6(g) and (h) below. The
ground-based NDB or DME facility may be temporarily out of service
during these operations. Charting will not change to support these
operations.

---- end quote ---

--
Peter

"Thomas Borchert" > wrote in message
...
> Hi all,
>
> a question that has probably been asked before, but I couldn't find it
> in Google:
>
> Is it allowed to use an IFR-approach-certified GPS instead of a DME in
> a LOC-DME or VOR-DME approach that does not have a GPS-overlay?
>


See AIM 1-1-19(f)

john smith wrote:
> DME distances will be greater than GPS distances due to slant-range.

On approach, you're at low altitude and the difference will be in the noise.

>
> Thomas Borchert wrote:
>
>> Hi all,
>>
>> a question that has probably been asked before, but I couldn't find it
>> in Google:
>>
>> Is it allowed to use an IFR-approach-certified GPS instead of a DME in
>> a LOC-DME or VOR-DME approach that does not have a GPS-overlay?
>> Thanks!

Thomas Borchert > wrote in
:

> Hi all,
>
> a question that has probably been asked before, but I couldn't find it
> in Google:
>
> Is it allowed to use an IFR-approach-certified GPS instead of a DME in
> a LOC-DME or VOR-DME approach that does not have a GPS-overlay?
>
> Thanks!
>

Yes, you may, but you have to aware that the GPS may not contain the LOC
station in its database. VOR stations should be fine.


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Andrew Sarangan wrote:
> Thomas Borchert > wrote in
> :
>
>
>>Hi all,
>>
>>a question that has probably been asked before, but I couldn't find it
>>in Google:
>>
>>Is it allowed to use an IFR-approach-certified GPS instead of a DME in
>>a LOC-DME or VOR-DME approach that does not have a GPS-overlay?
>>
>>Thanks!
>>
>
>
> Yes, you may, but you have to aware that the GPS may not contain the LOC
> station in its database. VOR stations should be fine.

And if that's the case you look at the little numbers on the approach
plate that give distances along final. That's also how you can
determine the MAP on a VOR approach when the VOR is located off the airport.

Stan,

Thanks to all!

--
Thomas Borchert (EDDH)

True. But if there is a fix in the approach that is defined by a distance
from something that is in the GPS database, you can use that fix and the
distance from it as a substitute for the LOC distance. That works, but in my
opinion does require advance planning to calculate the relevant distances
from that fix and write them down. It's way too easy to make a mistake to do
the figuring in real time during the approach.

"Andrew Sarangan" > wrote in message
. 4...
>
> Yes, you may, but you have to aware that the GPS may not contain the LOC
> station in its database. VOR stations should be fine.

"Thomas Borchert" > wrote in message
...
> Hi all,
>
> a question that has probably been asked before, but I couldn't find it
> in Google:
>
> Is it allowed to use an IFR-approach-certified GPS instead of a DME in
> a LOC-DME or VOR-DME approach that does not have a GPS-overlay?
>

I have never seen an approach certified GPS that did not have all the
intermediate waypoints for flying such an approach stored in its database.
Instead of your having to figure out that XYZZY is 5 DME from the airport,
the GPS should be giving you distance to XYZZY directly, automatically
cycling to the next waypoint upon reaching XYZZY. At least, that is what the
Garmin and Bendix-King GPSs that I am familiar with do.

AIM does say that approach certified GPS may be used in lieu of DME for
approaches.

Some certifiec IFR approach GPS units don't contain the localizer as a
waypoint, so you can't get the LOC distance (required for some LOC/ILS
approaches) directly.

"C J Campbell" > wrote in message
...
>
> "Thomas Borchert" > wrote in message
> ...
> > Hi all,
> >
> > a question that has probably been asked before, but I couldn't find it
> > in Google:
> >
> > Is it allowed to use an IFR-approach-certified GPS instead of a DME in
> > a LOC-DME or VOR-DME approach that does not have a GPS-overlay?
> >
>
> I have never seen an approach certified GPS that did not have all the
> intermediate waypoints for flying such an approach stored in its database.
> Instead of your having to figure out that XYZZY is 5 DME from the airport,
> the GPS should be giving you distance to XYZZY directly, automatically
> cycling to the next waypoint upon reaching XYZZY. At least, that is what
the
> Garmin and Bendix-King GPSs that I am familiar with do.
>
> AIM does say that approach certified GPS may be used in lieu of DME for
> approaches.
>
>

C J Campbell wrote:
> "Thomas Borchert" > wrote in message
> ...
>
>>Hi all,
>>
>>a question that has probably been asked before, but I couldn't find it
>>in Google:
>>
>>Is it allowed to use an IFR-approach-certified GPS instead of a DME in
>>a LOC-DME or VOR-DME approach that does not have a GPS-overlay?
>>
>
>
> I have never seen an approach certified GPS that did not have all the
> intermediate waypoints for flying such an approach stored in its database.

That may be the case but my GPS is not approach certified, it is
terminal and enroute only and does not have the localizer shack as a
waypoint. Therefore I would have to use the OM(or other intersection)
as a waypoint and use the little numbers on the chart.


>
> AIM does say that approach certified GPS may be used in lieu of DME for
> approaches.

The GPS does not have to be approach certified, terminal/enroute works too.

Mick Ruthven wrote:
> Some certifiec IFR approach GPS units don't contain the localizer as a
> waypoint, so you can't get the LOC distance (required for some LOC/ILS
> approaches) directly.

Which ones don't have the localizer as a waypoint?

Newps > wrote:
> That may be the case but my GPS is not approach certified, it is
> terminal and enroute only and does not have the localizer shack as a
> waypoint. Therefore I would have to use the OM(or other intersection)
> as a waypoint and use the little numbers on the chart.

The DME ground station may not even be in "the localizer shack". On
runways with ILS's at both ends, it's common to only have a single DME
ground station at one end of the runway.

For example, look at the profile view for the HPN ILS-34
(http://www.myairplane.com/databases/approach/pdfs/00651I34.PDF). The
MAP is 0.6 miles from the threshold, but 1.8 DME. The reason is that
the DME is near the approach end of 16, a mile away from the 34
threshold.

There's no reason to have another one at the other end; both localizers
are on the same frequency (hence the paired DME freqs are the same), and
the DME station is omnidirectional.

The lat/long for airports is called the ARP (airport reference point),
usually located near the geographic center of the field. The localizer
is at the far end of the runway. If the approach calls for a DME from
the localizer, you cannot use GPS because there is no coordinate for
the localizer antenna array. Note that for a long runway, like the
11,500 foot long runways at KPIT, it could be more than a mile from
the end of the runway to the ARP.

The FAA is working to determine coordinates for these antennas, I have
heard.

Otherwise, your GPS will be more accurate than regular DME for VOR.

In article >,
(John Hamilton) wrote:

> The lat/long for airports is called the ARP (airport reference point),
> usually located near the geographic center of the field. The localizer
> is at the far end of the runway. If the approach calls for a DME from
> the localizer, you cannot use GPS because there is no coordinate for
> the localizer antenna array. Note that for a long runway, like the
> 11,500 foot long runways at KPIT, it could be more than a mile from
> the end of the runway to the ARP.
>
> The FAA is working to determine coordinates for these antennas, I have
> heard.

I find it hard to believe that the FAA doesn't know the location of the
localizer antennas down to the fraction of an RCH. Getting that
information published in databases may be a project, but I gotta believe
the information already exists somewhere inside the FAA.

"Roy Smith" > wrote in message
...
>
> I find it hard to believe that the FAA doesn't know the location of the
> localizer antennas down to the fraction of an RCH. Getting that
> information published in databases may be a project, but I gotta believe
> the information already exists somewhere inside the FAA.
>

They appear on Obstruction Charts, but not every airport has an Obstruction
Chart, nor are they readily available.

However, it's not the location of the localizer array that's needed, it's
the location of the DME antenna. The DME is channelized to the localizer
frequency, but the DME is not collocated with a localizer similar to a
VORTAC. The DME antenna associated with a localizer frequency is generally
located near the "localizer shack" which is offset a few hundred feet to the
side of the localizer course. The locations of these DME antennas could
easily be published in the A/FD just as other navaids are.

There's an expression I haven't heard in more than 20 years.

Roy Smith wrote:
> I find it hard to believe that the FAA doesn't know the location of the
> localizer antennas down to the fraction of an RCH.

John Hamilton wrote:
> The lat/long for airports is called the ARP (airport reference point),
> usually located near the geographic center of the field. The localizer
> is at the far end of the runway. If the approach calls for a DME from
> the localizer, you cannot use GPS because there is no coordinate for
> the localizer antenna array.

That's wrong. There is no rule that says you have to use the DME from
the localizer in order to use GPS. Any fix on the approach that allows
you to figure it out is fine.

The FAA already has localizer, glideslope, ILS/DME and other facility
coordinates for all published procedures and they're available on the
internet. If you want any facility coordinates, you can go to the AVN
database at this website;
http://avnwww.jccbi.gov/datasheet/

For a specific NAVAID, such as the OJZ LOC at WestChester County NY,
1. Select NAVAIDS (not AIRPORT NAVAIDS)from the drop down menu under
CHOOSE A SEARCH
2. Type OJZ (or whatever NAVAID ID you're looking for)in the VALUE block.
3. Click SUBMIT
4. Click on the appropriate ID link from the list that appears.

In this example, the LOC coordinates are listed in the LOCALIZER
section, but the ILS/DME coordinates are listed in the ILS/DME section.

If you wanted ARP data or threshold coordinates, select AIRPORTS under
CHOOSE A SEARCH, and use the full 4 letter ID for the airport in the
VALUE block.
(You could also get the localizer data by going to AIRPORT NAVAIDS, but
then the search value would be the 4 letter airport ID rather than the
LOC ID.)

JPH

Roy Smith wrote:
> In article >,
> (John Hamilton) wrote:
>
>
>>The lat/long for airports is called the ARP (airport reference point),
>>usually located near the geographic center of the field. The localizer
>>is at the far end of the runway. If the approach calls for a DME from
>>the localizer, you cannot use GPS because there is no coordinate for
>>the localizer antenna array. Note that for a long runway, like the
>>11,500 foot long runways at KPIT, it could be more than a mile from
>>the end of the runway to the ARP.
>>
>>The FAA is working to determine coordinates for these antennas, I have
>>heard.
>
>
> I find it hard to believe that the FAA doesn't know the location of the
> localizer antennas down to the fraction of an RCH. Getting that
> information published in databases may be a project, but I gotta believe
> the information already exists somewhere inside the FAA.

Dave Butler > wrote in message >...
> Mick Ruthven wrote:
> > Some certifiec IFR approach GPS units don't contain the localizer as a
> > waypoint, so you can't get the LOC distance (required for some LOC/ILS
> > approaches) directly.
>
> Which ones don't have the localizer as a waypoint?

The Northstar M3 Approach, for one.

John Hamilton wrote:
> The lat/long for airports is called the ARP (airport reference point),
> usually located near the geographic center of the field. The localizer
> is at the far end of the runway. If the approach calls for a DME from
> the localizer, you cannot use GPS because there is no coordinate for
> the localizer antenna array.

You're making a big assumption here, that a GPS doesn't have the localizer-DME
in its database.

Someone posted that the Northstar M3 does not have localizer DMEs in its database.

The two approach-certified GPS receivers that I've used, the UPSAT GX50 and the
Garmin 430, both -do- have localizer-DME locations in their databases.

> Note that for a long runway, like the
> 11,500 foot long runways at KPIT, it could be more than a mile from
> the end of the runway to the ARP.
>
> The FAA is working to determine coordinates for these antennas, I have
> heard.

As posted by others, the locations of the DME antennas are well known by the
FAA, and in fact are available in (some? many?) GPS reciver databases.

>
> Otherwise, your GPS will be more accurate than regular DME for VOR.

One is the Trimble Approach 2000 GPS.

"Dave Butler" > wrote in message
...
> Mick Ruthven wrote:
> > Some certifiec IFR approach GPS units don't contain the localizer as a
> > waypoint, so you can't get the LOC distance (required for some LOC/ILS
> > approaches) directly.
>
> Which ones don't have the localizer as a waypoint?
>

Thomas Borchert > wrote in message >...
> Hi all,
>
> a question that has probably been asked before, but I couldn't find it
> in Google:
>
> Is it allowed to use an IFR-approach-certified GPS instead of a DME in
> a LOC-DME or VOR-DME approach that does not have a GPS-overlay?
>
> Thanks!

Thomas,

in Canada, clearly yes. Approved GPS can be used in lieu of all
ground based naviagtion aids as stated in the A.I.P. 3.16.4.3.1. "GPS
may be used to identify all fixes defined by DME, VOR, VOR/DME and
NDB, including fixes that are part of any IAP, to navigate to and from
these fixes, ..." The only exception *may be* NDBs used for Missed
Approach Fixes; however, just with the last revision of the A.I.P. the
was some change in wording.

Do you know the rules in other European countries?

Gerd

Gwengler,

> Do you know the rules in other European countries?
>

Germany: No. DME required in all IFR-certified (yes, there is such a
thing) aircraft, no matter whether the pilot plans to use approaches or
procedures that require DME or not. ADF only required in IFR training
aircraft. Ask Cirrus, they know very well how to add a remote DME box
to their avionice by now, from all the aircraft going to Europe.

--
Thomas Borchert (EDDH)