R
Roger, Roger
Guest
Neither. Load the approach and follow the CDI. That is, according to Garmin, THE legal way to do it.
GPS in lieu of DME
- Thread starter lhornaday
- Start date
lhornaday
Well-Known Member
Doing it this way, what makes it a VOR/DME approach? You're not following anything other than the GPS CDI. My brain is fried from flying today but this doesn't make since right now. Seems like by that wording you could make any approach a GPS approach... NDB, localizer back course, ect... if you just follow the GPS CDI.
I am talking about a "VOR/DME", not a "VOR/DME or GPS"
KSCessnaDriver
Well-Known Member
Sure, for the arc portion of the approach, as that is the only way you've got guidance. But on the final approach segment, you have to be on the VOR, unless you happen to have a DME arc for the final approach segment, at which point you couldn't fly the approach anyway.
KSCessnaDriver
Well-Known Member
If the GPS is the only source of DME in the airplane, I know of no other way to legally fly a DME arc without using a GPS. Care to inform me how that's possible?
lhornaday
Well-Known Member
According to the Instrument Flying Handbook, 2009, page 7-29, the answer is no.
http://www.faa.gov/library/manuals/...andbook/media/FAA-H-8083-15A - Chapter 07.pdf
To Fly a DME Arc:
1. Verify aircraft GPS system integrity monitoring
is functioning properly and indicates satisfactory
integrity.
2. Select from the airborne database the facility providing
the DME arc as the active GPS WP. The only
acceptable facility is the DME facility on which the arc
is based. If this facility is not in your airborne database,
you are not authorized to perform this operation.
3. Maintain position on the arc by reference to the GPS
distance instead of a DME readout.
lhornaday
Well-Known Member
I have also reached a conclusion about using the GPS on non-GPS approaches such as a VOR/DME from what I am reading on page 7-29.
Using GPS as a substitute for ADF or DME is subject to the
following restrictions:
3. WPs, fixes, intersections, and facility locations to be
used for these operations must be retrieved from the
GPS airborne database.
and later..
If the fix is identified by a five-letter name which is
contained in the GPS airborne database, select either
the named fix as the active GPS WP or the facility
establishing the DME fix as the active GPS WP.
This is referring to how you can determine your position over a DME Fix, not how you can use it to navigate past the FAF. But to identity that FAF, you can load the GPS approach with the for guidance only limitation. You will be able to determine the position over that fix and any other that was pulled from the GPS database. You would of course, be required to navigate using the VOR, localizer, ect. that the approach requires. But the DME requirement is met as long as the fix is in the database and it is the active waypoint.
Any other thoughts?
Forgot to mention, that the other method is also legal - selecting the navaid from which the DME is based as the active waypoint and using it like a conventional DME system. That's how I've done it on the past few lessons since I wasn't sure about the overlay situation.
Using GPS as a substitute for ADF or DME is subject to the
following restrictions:
3. WPs, fixes, intersections, and facility locations to be
used for these operations must be retrieved from the
GPS airborne database.
and later..
If the fix is identified by a five-letter name which is
contained in the GPS airborne database, select either
the named fix as the active GPS WP or the facility
establishing the DME fix as the active GPS WP.
This is referring to how you can determine your position over a DME Fix, not how you can use it to navigate past the FAF. But to identity that FAF, you can load the GPS approach with the for guidance only limitation. You will be able to determine the position over that fix and any other that was pulled from the GPS database. You would of course, be required to navigate using the VOR, localizer, ect. that the approach requires. But the DME requirement is met as long as the fix is in the database and it is the active waypoint.
Any other thoughts?
Forgot to mention, that the other method is also legal - selecting the navaid from which the DME is based as the active waypoint and using it like a conventional DME system. That's how I've done it on the past few lessons since I wasn't sure about the overlay situation.
Mike H
Well-Known Member
If a fix.waypoint,intersection or facility is part of an approved instrument procedure, IT'S IN THE DATABASE- unless the database is out of date, in which case you'd better not be using it for anything other than situational awareness anyway
KSCessnaDriver
Well-Known Member
What? There is nothing in the regulations that prohibit use of an expired database for IFR operations during en-route operations. Many of the supplements provided with the GPS do, however.
And yet, you still never answered how you navigate a DME arc without using GPS if the only DME you have is a GPS.
lhornaday
Well-Known Member
Read what you quoted carefully and in the right context. You can use fixes in the database to identify your location over that fix in lieu of DME. It does not say that you can use a GPS to fly point to point in replacement of using DME.
The handbook gives clear instructions on flying a DME arc with GPS DME. But I agree that you could fly it loading it into the GPS as an approach. But there is nothing to say that it is legal.
We can't just replace routes because we have point to point navigation by GPS. Flying a DME arc with no DME displayed would be the same thing as flying an NDB approach by GPS without ever tuning the ADF.
R
Roger, Roger
Guest
Right, you have to have follow the VOR FOR THE FINAL APPROACH COURSE. Unless you're doing the VOR/DME 15 at KMTN, you do what Garmin says and follow the GPS CDI on the arc and have no quandary. In the case of that approach, I'm not sure of the legal way to fly it with GPS in lieu.
Pilot Hopeful
Well-Known Member
Well that certainly is a neat observation. Is a DME readout considered "lateral guidance" on an arc? If so, then a GPS substitution is not permissible. If not, then loading the approach in the GPS unit should be alright. Any guru advice here?
If we cannot fly a GPS overlay, then at least the airport has a GPS approach available. We could go in that way!
lhornaday
Well-Known Member
I've still yet to find an official source that says you can fly a DME arc on an ILS or VOR approach with GPS guidance only. Except that someone who knows someone said that the FAA has written that is ok. So there may be a LOI. I've already quoted the IFR handbook which says you can not unless you select the facility from the db. I've seen the same on AOPA.
The Garmin handbook states that the GPS will guide you around an arc, but if you look at the chart, it is one of the VOR or GPS approaches. The manual gives no guidance for VOR or ILS approaches. That was the 430 manual. I will review others when I get time.
I've read on good article on a method to see the arc course on the GPS display but still have the navaid as the active waypoint:
http://simfliteminnesota.blogspot.com/2007/10/substituting-gps-for-dme-and-adf.html
Pilot Hopeful
Well-Known Member
Some observations:
1) The article references AIM text that no longer exists. For example, that article states that AIM 1-1-19(f)(c)(2)(b) talks about using GPS to fly a DME arc: “You must select from the airborne database the facility providing the DME arc as the active GPS waypoint. Note: The only acceptable facility is the DME facility on which the arc is based. If this facility is not in your airborne database, you are not authorized to perform this operation.” Current AIM text for this reference differs.
2) The referenced text DOES appear in the Instrument Procedures Handbook (IPH), as you noted.
3) The IPH has traditionally reflected and restated AIM text.
4) A G1000 exercise manual states that the G1000 may be used to navigate along a DME arc on approach as long as the arc is included in the database.
I wonder if the requirement to make the DME facility an active GPS waypoint has been dropped from the AIM, though its reference still appears in the IPH? If so, we have a potentially ambiguous scenario.
Is a database arc sufficient when flying a stand-alone VOR or ILS approach? (That is your question too, I realize.) Garmin says "yes"; an official reference would be ideal. My hunch is that Garmin may be correct and that the IPH should be updated. Let the search continue!
Interesting: When the IPH shows G1000 screenshots for flying the DME arc on the ILS7L approach at DAB, the database arc (i.e., the one loaded with the approach) is depicted! (See figures 7-19, 7-20, 7-21) There is no mention of needing to make OMN the active waypoint. Is this an oversight or evidence that a database arc is sufficient?
lhornaday
Well-Known Member
You're right. It was dropped from the AIM. Interesting enough the list of changed to the AIM did not describe the reason for dropping it. Only to clarify some other points about ensuring the database is good.
All the other references I have are also old. However, there is nothing new that states otherwise.
I'm not a big G1000 guy. Is there usually a separate DME source? Two GPSs or other DME?
All the other references I have are also old. However, there is nothing new that states otherwise.
I'm not a big G1000 guy. Is there usually a separate DME source? Two GPSs or other DME?
KSCessnaDriver
Well-Known Member
That's how I was always taught how to do it. As a secondary, you could tune in the VOR in the navigation radio and then set the VOR as the active waypoint, in order to get the DME from the VOR. Either way, it works the same.
lhornaday
Well-Known Member
That would be optimum and satisfy everyone. Problem is my student's plane doesn;t have separate DME and this type of approach is very common around these parts. I'm certain he'll do one on the checkride. So the G1000 does have another DME?
Autothrust Blue
Welcome aboard the Washington State Ferries
G1000 DME is displayed on the primary flight display under the HSI and is a function of what you've set the RDMI (bearing pointers) up to display. I don't have a PFD in front of me, but if you push PFD then BRG1/BRG2 you can cycle through nav sources for the bearing pointers and the DME boxes. The sources are VOR1, VOR2 and GPS if memory serves.
KSCessnaDriver
Well-Known Member
Most of the G1000 setups don't have an actual DME box, its all GPS data. It is an option, but you don't see it very often on 172/182's. Lots of money for something that is of very limited use, especially in the G1000 setup.
Sounds right, except you could set the bearing pointers to whatever navigation source you've got. VOR1, VOR2, GPS, NDB, or whatever else you might have interfaced with the G1000.
Autothrust Blue
Welcome aboard the Washington State Ferries
So, is it a /U airplane without a current GPS database, if there's no actual DME? :dunno: