Tag Info

17

Mighty interesting! There is a clue in the FCOM: Four frequencies per FMGC If you check FCOM Chapter 22 § 20-20-30 you'll note it says: Each FMGC [Flight Management and Guidance Computer] automatically uses its four DME frequencies as follows: One DME frequency for display. It is possible to tune it manually or automatically. This DME frequency is also ...

14

We can find the exact method to use online, after all this is a common 3D trigonometry problem. I'll use Michael Geyer US DoT report: Earth-Referenced Aircraft Navigation and Surveillance Analysis. The principle is: The two DME distances determine two spheres which intersection is a circle. The aircraft is on this circle. The aircraft altitude determines a ...

12

There's no accurate and simple way to know the height above the station in order to do the calculation with the existing equipment. Altitude is not an indicator as the DME station may be above sea level. If your airplane is at 15,000ft and the station is at sea level you'll get one answer, if the station is at 10,000ft you'd get a completely different result,...

9

Apart from the fact that it is required to learn, the obvious "benefit" is that you know what to do when flying to an airport that uses a DME Arc approach. RNAV/GPS approaches are becoming more common, but have far from taken over from conventional approaches. Even if an airport has radar, it does not necessarily mean that radar vectoring for final approach ...

6

As the Wikipedia article states, there are two modes - SEARCH and TRACK. In SEARCH mode, the DME interrogates with up to 150 pulse pairs per second. Similarly, in TRACK mode it interrogates at up to 30 PP/S. What it doesn't say is that the interrogations are not evenly spaced at a fixed rate. The DME uses a pseudorandom number generator to vary the ...

4

"Lock-on" just refers to a unit receiving multiple different response signals in response to its interrogation broadcasts, scanning for the signal it's looking for, and when it finds the signal who's encoding matches its channel selection, it starts to process that signal and ignores all others. It's locked on to that signal.

4

You have to realize that the DME is a justified and ancient nav system. When it was concieved, it was chosen to keep it simple, for obvious reasons. As it is, it does not have to communicate with any other system, making it a very reliable stand alone device. There is no need to create a "DME 2.0", we already have gps and other more sophisticated systems ...

3

For UAS, the aircraft may be below the service volume of a VORTAC most of the time. Furthermore in the US sUAS are normally line of sight to the pilot so in theory if GNSS is unavailable, the pilot will control visually. Finally the variability and uncertainty of VORTAC is high enough so as to make it impractical for UAS stability, drift and position ...

3

Just to be clear, when you are asked for your DME from a station or using a DME fix, what is being expected is that you use what you see as the distance in nautical miles on the DME readout of your instrumentation. You're not expected to use your altitude to come up with the distance along the ground using trigonometry. It's the slant distance they're ...

3

If your radio has DME installed, then it is shown on the instruments

2

How can DME signal go from the station? Your aircraft's DME sends a signal (when tuned to an appropriate frequency) to the ground station (suitably equipped with DME, e.g. Vortac, ILS/DME, etc.) and the station sends back an electronic reply. The aircraft's DME will measure how much time it took for the signal to travel to/from the station and translate ...

2

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). 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.

1

First; you have to understand that ARINC 424 is an industry standard. It is not regulatory. The regulatory documents are published by RTCA (and EUROCAE in the EU). The basic database coding requirements of it are generally well accepted and used by the industry as those are essential to its primary function of interoperability. But there's a lot of ...

1

Labels 246 and 247 describe up to 4 7-bit ASCII characters. 1th char: Bits 11-17 of 246 2th char: Bits 19-25 of 246 3th char: Bits 11-17 of 247 4th char: Bits 19-25 of 247 For AGG, in ASCII we get 0x41, 0x47, 0x47, then: Label 246 = 0x11D04A6 Label 247 = 0x11CA7 SSM encoding is the same as regular discrete labels. I am not familiar with labels 242/244.

1

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: Press the PFD Softkey. Press the DME Softkey to display the DME Information Window. To remove the DME Information ...

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