DME soft key

[dmloftus]

TMI Rich! (the dog, not the DME) ;-)

[yl472401]

I reviewed the picture that was sent to me prior the aircraft purchase, the soft key wasn't there. I guess that solved half of the mystery. The other half would be as CFIDave mentioned as if the proper software was installed. I reviewed the G1000 Diamond study tutorial. It states that the ADF/DME is optional. But, I saw it with my own eyes there were DME information showing up on the screen during at least one flight, likely during the GPS, RNAV usage. with that being said, could this DME information part of the GPS navigation system??

For DME, I usually use the GPS Direct-To the fix, ie VOR, etc. You're usually using the VOR as primary guidance (ie CDI on VOR1) and you will get the GPS-derived DME at the top of the PFD from the GPS. Not sure why a separate DME receiver would be needed unless you were just using the full GPS plan for reference and needed a fully independent DME. I think most of those procedures are going away, my home airport deleted their DME arc procedure recently.

Got it. So, the DME is essentially a back up Navi system.


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[yl472401]

I'm not sure if these equivalents are available in the G1000, but for DME to VOR I tune the 530 to the desired frequency and it continuously update distance and radial from said VOR regardless whether I'm actually using the VOR for navigation.

The 430 doesn't do this, but both GNS units can be caused to display a "Nearest VOR" list, which displays frequencies and dynamically updates distance and bearing to each entry.

I think yours might have a dedicated DME unit installed and that’s why while you uses VOR as your Navi, you can still get the DME info. That’s just my educated guess.


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[yl472401]

It has been a mystery to me for a while. Whenever I study some online video about G1000 navigation, the DME/ADF soft key has been showing up as an option. But I could never get my DME soft key to show up. Is there a special process to get it to show up? I'm trying to use it for VOR distance measurement.
Thanks.

Bryan, I might well be misunderstanding what you're looking for in DME, but here's what I use when I want real-time DME readings (see screen capture below):
-- set a couple VORs (I have RZS and GVO set in this example)
-- on the PFD, press the PFD softkey
-- click BRG1 until the first VOR shows
-- click BRG2 until the second VOR shows
Now on the PFD below the HSI there are shown DMEs to each of the selected VORs. Tiny caveat... these are not the slant distances that an actual DME device would sense, but rather horizontal distances provided by the GPS.

Best regards,
Wayne

Thanks for the heads up. Do you mind post a picture of the soft keys you see on your PFD? I’m trying To figure out if your aircraft has the dedicated DME unit or not ?


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[waynemcc999]

Thanks for the heads up. Do you mind post a picture of the soft keys you see on your PFD? I’m trying To figure out if your aircraft has the dedicated DME unit or not ?


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Bryan, almost certainly my aircraft (2008 XLS) does not have a DME unit installed... and aside from widespread GPS outage as Russ describes (of the government-run system itself, as we all fly with several backups to the in-panel avionics), I personally see ZERO reason to have an actual DME unit.
My aircraft is in the shop (new prop finally installed, awaiting full annual signoff), so the screen image I posted was from my home sim.
Wayne

[yl472401]

Thanks for the heads up. Do you mind post a picture of the soft keys you see on your PFD? I’m trying To figure out if your aircraft has the dedicated DME unit or not ?


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Bryan, almost certainly my aircraft (2008 XLS) does not have a DME unit installed... and aside from widespread GPS outage as Russ describes (of the government-run system itself, as we all fly with several backups to the in-panel avionics), I personally see ZERO reason to have an actual DME unit.
My aircraft is in the shop (new prop finally installed, awaiting full annual signoff), so the screen image I posted was from my home sim.
Wayne

Thanks Wayne!! I will follow the process you mentioned and see if I can bring up the needed DME info.


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[Rich]

You could be off as much as the tangent of your angle to the fix. On a 3 degree glideslope that's not much, 5.2%. But if you were navigating IFR between VOR's at high altitude for, say a ridge crossing requiring an altitude change, it could be more significant. Great point.

A light dawned this morning, so I thought I'd make a correction: The discrepancy between slant and horizontal distance would be measured by the cosine of the angle, not the tangent. The cosine of 3 degrees is .9986, making the discrepancy .14%. At 10 miles, that comes to roughly 84 ft. (about 2 wingspans). This would be the same for, say, flying a 10nm DME arc 3,000 ft above the fix.

[yl472401]

Was it truly an apple that landed on your head, Sir?

You could be off as much as the tangent of your angle to the fix. On a 3 degree glideslope that's not much, 5.2%. But if you were navigating IFR between VOR's at high altitude for, say a ridge crossing requiring an altitude change, it could be more significant. Great point.

A light dawned this morning, so I thought I'd make a correction: The discrepancy between slant and horizontal distance would be measured by the cosine of the angle, not the tangent. The cosine of 3 degrees is .9986, making the discrepancy .14%. At 10 miles, that comes to roughly 84 ft. (about 2 wingspans). This would be the same for, say, flying a 10nm DME arc 3,000 ft above the fix.

[Rich]

Was it truly an apple that landed on your head, Sir?

You could be off as much as the tangent of your angle to the fix. On a 3 degree glideslope that's not much, 5.2%. But if you were navigating IFR between VOR's at high altitude for, say a ridge crossing requiring an altitude change, it could be more significant. Great point.

A light dawned this morning, so I thought I'd make a correction: The discrepancy between slant and horizontal distance would be measured by the cosine of the angle, not the tangent. The cosine of 3 degrees is .9986, making the discrepancy .14%. At 10 miles, that comes to roughly 84 ft. (about 2 wingspans). This would be the same for, say, flying a 10nm DME arc 3,000 ft above the fix.

I have about 30 seconds of extreme lucidity at 4:00 AM each day

[dmloftus]

Was it truly an apple that landed on your head, Sir?

A light dawned this morning, so I thought I'd make a correction: The discrepancy between slant and horizontal distance would be measured by the cosine of the angle, not the tangent. The cosine of 3 degrees is .9986, making the discrepancy .14%. At 10 miles, that comes to roughly 84 ft. (about 2 wingspans). This would be the same for, say, flying a 10nm DME arc 3,000 ft above the fix.

I have about 30 seconds of extreme lucidity at 4:00 AM each day

Haha! Yes, 40 years since trig. Thanks for the correction