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Use of GPS in lieu of ADF and DME, was: Converting IFR GPS t

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BobsV35B(at)aol.com
Guest

Posted: Thu May 04, 2006 6:42 pm Post subject: Use of GPS in lieu of ADF and DME, was: Converting IFR GPS t

Good Evening Richard,

 

Your sleuthing is done in a reasonable manner, but that isn't quite the way  

it works.

 

What I stated is correct.

 

A GPS that has at least an IFR approval for enroute and terminal use can be  

used for any ADF or DME use other than what I specified.  If the DME  is 

included in the name of the approach or if it is listed a in a note on the  

approach page, the approach can be executed by using the GPS in the manner  described 

in the AIM section 1-1-19, f.

 

The GPS cannot be substituted for the ADF when executing an NDB approach.  

You must name an alternate that does not need a GPS or any other equipment you  

do not have on board and you must have a current data card in the set.  All  

points of navigation must be contained in the database and cannot be self 

loaded  by the operator. 

 

However, there is one very unusual case where you may use another point  

along the same course to determine a waypoint via the GPS distance from  another 

waypoint along that course.

 

For all practical purposes within the US National Air space System, the GPS  

can be used in lieu of ADF and DME..  If you find any FAA inspector who  tells 

you otherwise, please send me his name and station within the FAA. I will  

contact Oklahoma City and see to it that the person gets the proper  information.

 

You state: "That is why/how approaches are named and why some are titled  

"NDB or GPS"

and others are titled "NDB".  Why would there be a  difference if GPS could

be substituted for any [all] NDB's.  For  reference look up the [Anderson]

AID NDB or GPS rwy 30 approach and compare  it to the [Angola] ANQ NDB rwy5

approach."

 

As I said earlier, you cannot use the GPS as a substitute for the ADF on  any 

NDB approach.  When the Title says "NDB or GPS", that means that the  

approach has been approved for use by GPS under the old, no longer used, overlay  

program. All of the points within the approach are in the database and the  

approach is executed strictly as a GPS approach.  When you execute that  approach, 

you are NOT substituting the GPS for the ADF, you are shooting a GPS  approach 

that has the same courses and uses the same minima as the NDB  approach.

 

If it is an ILS and DME is in the title or if DME is listed as being  

required on a note in the approach, the GPS may be used in lieu of the DME. You  are 

not shooting a GPS approach you are using the DME to determine the distance  

from the location of the DME transceiver.

 

However, if an approach is titled just as an NDB approach, you cannot  

substitute the GPS for the ADF.

 

You further state:

 

"I'm not the expert, so someone may want to verify (or correct me) on  this.

The whole topic can be pretty confusing.  I'll do some digging  myself for

appropriate AC, FAR, and/or AIM references:

 

This is one of the very few cases where I can call myself an expert! I  was 

one of the very early proponents of such use.  The fine folks at  AOPA joined 

in on my side and we got the job done! 

 

I was even asked by the FAA to aid in writing the provisions to allow that  

use.

 

By the time the interpretations had been written, some of the language got  

pretty convoluted.  Without getting a lawyer to cover everything I have  said 

about it, I will not claim one hundred percent accuracy in my description,  but 

the simple answer is that the GPS can be used in lieu of ADF or DME on any  

approach in the manner I have described. You are reading too much into it. Read 

 the AIM and you will see the intent!

 

Unfortunately, the fellows that did write that language have either retired  

or moved on to bigger an better things. That is why I ask that if anyone in 

the  FAA tells you different, please let me know and I will chase it down for 

the  proper answer.

 

I would be happy to discuss the specifics of any individual approach or  

application that you would like to have explained.

 

Happy Skies,

 

Old Bob



In a message dated 5/4/2006 5:09:04 P.M. Central Standard Time,  

rtitsworth(at)mindspring.com writes:




<rtitsworth(at)mindspring.com>



FYI...



Someone may want to  further investigate/verify this but I believe the

following comment (from  below) is not 100% legally correct.



"It [GPS] can be used for all  enroute and terminal purposes including as a  

substitute for the ADF  and DME on any approach that requires those items."



I believe the  correct comment is:



The GPS can be used for the ADF and/or DME on  "most" (not "any") approach

that requires those.



The nuance is  where/why the NDB and/or DME is required for the approach....



If the  requirement is in the title (name) of the approach, then the NDB

and/or DME  facility is necessary for the final leg (FAF -> Runway) and

CANNOT be  substituted with the GPS unless GPS is also in the title (it

frequently is  for many NDB approaches, but not "all").



That is why/how approaches are  named and why some are titled "NDB or GPS"

and others are titled  "NDB".  Why would there be a difference if GPS could

be substituted  for any [all] NDB's.  For reference look up the [Anderson]

AID NDB or  GPS rwy 30 approach and compare it to the [Angola] ANQ NDB  rwy5

approach.



http://download.aopa.org/iap/20060413/EC-2/aid_ndb_or_gps_rwy_30.pdf

http://download.aopa.org/iap/20060413/EC-2/anq_ndb_rwy_05.pdf



If  you page though an approach plate book you'll find similar examples.  



However, if the required NDB and/or DME facility is for another part  of the

approach, such as the missed procedure or an approach with a single  IAF,

then it will appear on the plan view as text such as "DME  Required".  The

GPS CAN be used as a substitute for these (i.e. the  DME is not required - a

bit counter-intuitive)



For example reference  the [Akron] AKR LOC rwy25 approach (where the NDB is

the only  IAF):



http://download.aopa.org/iap/20060413/EC-2/akr_loc_rwy_25.pdf



If  the NDB and/or DME is used for another aspect of the approach or  an

optional IAF or alternate DME minimum then it will not be noted as  required

and the GPS CAN also be substituted.



The GPS can also be  substituted for IFR enroute fixes (assuming the aircraft

is also equipped  with "ground based navigational instruments appropriate to

the  flight").  I understand that to mean that you must have some  appropriate

ground based equipment on board and functional (i.e. a  VOR).



I'm not the expert, so someone may want to verify (or correct me)  on this.

The whole topic can be pretty confusing.  I'll do some  digging myself for

appropriate AC, FAR, and/or AIM references.



Rick  Titsworth

C172 w/Bendix King KN94 IFR Cert GPS (enroute and  approach)





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rtitsworth

Joined: 16 Jan 2006
Posts: 76
Location: Detroit, Mi

Posted: Thu May 04, 2006 9:19 pm Post subject: Use of GPS in lieu of ADF and DME, was: Converting IFR GPS t

Thanks. Good info. 



Now that I've found an expert I have three nuance questions...



#1 If someone has a GX-65 (enroute only) do they still file as /G?

Does that create any confusion with ATC if they are asked/vectored for a GPS

approach?

#2 Lets say my IFR GPS database is out of date (most recent updates not yet

applied).



I understand that I can still use the GPS for enroute navigation (i.e. file

and accept "direct") as long as I verify that the relevant data points are

still accurate.



I understand that I cannot use it for IFR GPS approaches (until updated).



Would I file /G?  



Do you know of the AC/FAR/Aim reference to this scenario?

#3 Continuation of scenario #2...  If I am flying a VOR/DME or LOC/DME or an

ILS with a required ADF (for the missed) with a traditional and valid

NAV/CDI, can I legally use the out-of date GPS to substitute the DME or ADF

if I have verified the accuracy of the relevant GPS data?  Do you know of

the AC/FAR/Aim reference to this scenario?



Thanks Again.

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