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For some strange reason I cannot seem to find any information about what button to push on the instrument panel to active the DME. There is plenty of information about how DME works with interrogation and slant distance, but I cannot seem to locate any information about what button to actually push to activate DME when I am sitting in the cockpit (in a Cessna 172, for example) or where to look on the instrument panel to read the measured distance the DME is telling me. So if the DME is measuring 8 nautical miles, where on the instrument panel will that "8" be displayed?

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    $\begingroup$ If I asked you "what button do I press in my car to turn on the air conditioning?", could you tell me? Without any information about the car model or interior? Even the same model of aircraft can have completely different avionics and instruments. To get an answer, you need to tell us what aircraft you have and exactly which instruments you have in your cockpit. For example, do you have an integrated glass panel like the G1000? Or traditional 'steam gauges'? Or something else? If you don't know how to identify the instruments, a picture would be very useful. $\endgroup$
    – Pondlife
    Jul 3 '20 at 5:57
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    $\begingroup$ I'm voting to close as there's not enough information to answer. Is DME even equipped on the airplane? In many training organizations airplanes have very different instrument fits, there's no way to guess reliably. $\endgroup$
    – GdD
    Jul 3 '20 at 14:55
  • $\begingroup$ Wow, tough crowd. My question was answered adequately by Jamiec. $\endgroup$
    – SurfandSky
    Jul 5 '20 at 5:27
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Typically, there isn't a "button" as such, you tune the DME to the frequency of the ground station (or slave it to the NAV radio).

DME

The knob on the right is used to tune a frequency (shown before MHZ) when in "frq" mode, which is usually a VOR/DME. The numbers before NM is your distance to/from the station in Nautical Miles.

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  • $\begingroup$ This answer makes sense to me. None of the steam-gauge Cessna airplanes I have flown have had a separate module for DME, which explains why I was confused about which button to press to activate it. $\endgroup$
    – SurfandSky
    Jul 5 '20 at 5:18
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For the classic DME instrument, see Jamiec's answer.

If your aircraft is equipped with a G1000 glass cockpit, the DME window needs to be enabled via the PFD menu using the buttons at the bottom of the PFD:

Displaying the DME Information Window:

  1. Press the PFD Softkey.
  2. Press the DME Softkey to display the DME Information Window.
  3. To remove the DME Information Window, press the DME Softkey again.

Displaying the DME Information Window

The Window will then be shown to the left of the HSI at the bottom of the PFD:

DME INFORMATION WINDOW

The DME Information Window is displayed above the BRG1 Information Window on the 360° HSI and in a box above and along side the Arc HSI. It shows the DME label, tuning mode (NAV1, NAV2, or HOLD), frequency and distance. When a signal is invalid, the distance is replaced by -.-- NM. Refer to the Audio Panel and CNS Section for information on tuning the DME.

DME Information Window


Source: Garmin G1000 Manual - Cessna Nav III

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    $\begingroup$ Haha yeah. Number of times I've seen a G1000 in a C172 - once. X-Plane :D $\endgroup$
    – Jamiec
    Jul 3 '20 at 8:29
  • $\begingroup$ @Jamiec All new C172s have the G1000, but I bet more than 90% of the world's C172s are still using steam gauges ;) $\endgroup$
    – Bianfable
    Jul 3 '20 at 8:32
  • $\begingroup$ Indeed, every C172 i've flown is pre-1990 $\endgroup$
    – Jamiec
    Jul 3 '20 at 8:33
  • $\begingroup$ @Jamiec - Yes, G1000 availability is highly dependent on the model. I’ve never seen a C172S or SP in real life without a G1000. Then again, I’ve never seen a C172E, G, L, M, or N with a G1000. Although, I have seen the older models retrofitted with Aspen and Dynon systems. $\endgroup$
    – Dean F.
    Jul 3 '20 at 16:17
  • $\begingroup$ @Jamiec: Heck, every airplane I've flown is pre-1975. $\endgroup$
    – jamesqf
    Jul 4 '20 at 4:59
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Both Jamiec’s and Bianfable’s answers are right for the avionics equipment represented in their posts. Your actual answer will depend on what equipment you have in your aircraft. In my own recent experience, I have not seen an operable DME radio in a Cessna 172. I’ve only seen one operable ADF in a Cessna 172. In most cases, they will look like smaller versions of your NavCom radio. Mainly, I see at least one of the NavCom radios retrofitted to a GPS unit like the Garmin G430 or G530. This is a preferable expense than maintaining technology that is becoming increasingly obsolete. And, per AIM 1-2-3, RNAV/GPS can be substituted for DME.

If you are flying a glass panel aircraft like one equipped with a G1000, G500, or Dynon Skyview, the GPS distance to your selected point will be displayed on your PFD and is an option on your MFD. This can be found in the top info bar of your PFD. As long as the position of the NavAid is updated in your GPS database, you can select it as a fix and use this distance for navigational purposes.

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