GPS for DME?

[52Vincent]

mizzouguy If you use the GPS for DME on an ILS you must put the GPS direct to the ILS identifier such as I-JQX. And where did Jeff get his info. Most GPS's are IFR certified. I haven't seen too many panel mounted ones any more that arent.

Is there a difference between loading the ILS identifier into the GPS or loading the approach? Would not the DME information be the same?

 

[Thedude]

In short, no you can not use GPS to substitue ILS DME or VOR for that matter.

GPS dist while in the arrival area of an airport is a great tool for situational refrence esp when no DME is available from your NAV-aid

All GPS that are panel mounted are not IFR Certified. That costs extra and is specfic to that aircraft.

Not all GPS will accept I-xxx for a waypoint

 

[52Vincent]

In short, no you can not use GPS to substitue ILS DME or VOR for that matter.

GPS dist while in the arrival area of an airport is a great tool for situational refrence esp when no DME is available from your NAV-aid

All GPS that are panel mounted are not IFR Certified. That costs extra and is specfic to that aircraft.

Not all GPS will accept I-xxx for a waypoint

This is confusing, simply due to the fact that most of the new 172's come equipped with GPS and no DME, therefore flying any approach with DME required is not possible in most 172 SP models, providing the GPS is not IFR certified "I guess????"
When programming the GPS for some precision and non-precision approaches you recieve the reminder indicating that GPS guidance on approaches is strictly for monitoring only-use the VLOC recivers and external CDI (or HSI) for primary navigation.
Does this mean I cannot use the GPS for DME information or just that I cannot monitor the approach on the GPS? If thats the case what do I use for DME?

 

[Singlecoil]

To say the GPS is or is not IFR certified is not quite the whole picture. There are 3 different levels of IFR certification: IFR enroute/terminal, IFR remote/oceanic, and IFR enroute/terminal/approach. It sounds like the 172 has an IFR enroute/terminal installation if it is giving you a warning when you load an approach. However, the AIM clearly states that this installation is legal to use for DME/ADF, that is why there is no other DME or ADF installed.

It was stated above that you have to pull the fix from the database, and the database must be current. However, if the fix is not in the database, the AIM gives you guidance to use one that is, provided it is along the same azimuth from the station.



From the AIM:

(1) To determine the aircraft position over a DME fix:

[a] Verify aircraft GPS system integrity monitoring is functioning properly and indicates satisfactory integrity.

If the fix is identified by a five letter name which is contained in the GPS airborne database, you may select either the named fix as the active GPS waypoint (WP) or the facility establishing the DME fix as the active GPS WP.

NOTE-
When using a facility as the active WP, the only acceptable facility is the DME facility which is charted as the one used to establish the DME fix. If this facility is not in your airborne database, you are not authorized to use a facility WP for this operation.

[c] If the fix is identified by a five letter name which is not contained in the GPS airborne database, or if the fix is not named, you must select the facility establishing the DME fix or another named DME fix as the active GPS WP.

NOTE-
An alternative, until all DME sources are in the database, is using a named DME fix as the active waypoint to identify unnamed DME fixes on the same course and from the same DME source as the active waypoint.

CAUTION-
Pilots should be extremely careful to ensure that correct distance measurements are used when utilizing this interim method. It is strongly recommended that pilots review distances for DME fixing during preflight preparation.

[d] If you select the named fix as your active GPS WP, you are over the fix when the GPS system indicates you are at the active WP.

[e] If you select the DME providing facility as the active GPS WP, you are over the fix when the GPS distance from the active WP equals the charted DME value and you are on the appropriate bearing or course.

Link to the AIM