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17 votes
Accepted

How can I triangulate a position using two DMEs?

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. ...
mins's user avatar
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12 votes
Accepted

Why don't aircraft have DME that can automatically convert the slant range to ground range?

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 ...
GdD's user avatar
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11 votes
Accepted

Are there two navaids on the same frequency close enough to be confused?

Short answer ICAO recommendations include a protection for same-frequency navaids, restricting the received power of undesired stations to a level preventing interferences. To meet this restriction ...
mins's user avatar
  • 74k
10 votes

Are there benefits in training instrument students how to fly a DME arc?

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,...
60levelchange's user avatar
7 votes
Accepted

How does an airborne DME unit differentiate itself?

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 ...
Gerry's user avatar
  • 19.9k
5 votes

Why don't aircraft have DME that can automatically convert the slant range to ground range?

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 ...
Jpe61's user avatar
  • 28.8k
4 votes

What does it mean to "lock on" to a DME ground station?

"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 ...
John K's user avatar
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4 votes
Accepted

What are the modulation parameters of a DME?

DME principle Source. The interrogator sends a pair of pulses, the DME transponder sends back identical pulses after a fixed delay of 50 μs for X channels, 56 μs for Y channels. The interrogator is ...
mins's user avatar
  • 74k
3 votes

"w/o DME" minimums on DME required approach

DME is required equipment for the approach procedure, but note that the LOC DME minimums only apply to the Localizer DME functioning. The missed approach holding pattern references the VORTAC DME, ...
Romeo_4808N's user avatar
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3 votes
Accepted

Do UAVs use ground-based navaids?

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 ...
mongo's user avatar
  • 17.8k
3 votes

How can I know DME distance?

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 ...
Terry's user avatar
  • 39.2k
3 votes

How can I know DME distance?

If your radio has DME installed, then it is shown on the instruments
Afe's user avatar
  • 1,501
3 votes

Are there two navaids on the same frequency close enough to be confused?

#1 I don't know. #2 On December 20, 1995 American Airlines 965 crashed into a mountain top near Cali Columbia when it was flying down the the valley between mountains and the 757 autopilot turned the ...
JetCityMatt's user avatar
  • 1,125
2 votes

How can the A320 receive 3 DME signals if it has only 2 DME receivers?

My FCOM says: Each FMGC automatically uses its five DME frequencies as follows: One DME frequency for display. It is possible to tune it manually or automatically. Two DME frequencies in DME/DME ...
Alex Hoff's user avatar
2 votes
Accepted

What button do I push on the instrument panel to activate DME in VOR navigation?

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 ...
Jamiec's user avatar
  • 33.3k
2 votes

Timing not authorized for defining the MAPt

Per TERPS 2-9-8(c), this can happen when there is excessive fix error on the PFAF (precise final approach fix) and there are obstacles on the missed approach segment. The fix error on the PFAF is not ...
Chris's user avatar
  • 15.9k
2 votes

Timing not authorized for defining the MAPt

There are two cases for this mention to be added: The MAPt is collocated with a facility or a fix, there is no reason to use a timing from the FAF to identify the MAPt. This case is the one ...
mins's user avatar
  • 74k
1 vote

An Aircraft is a flight level 150 the DME is at sea level find maximum and minimum range?

Aside from the issues others have pointed out in the comments, the method of determining the minimum DME range display is straightforward. Since DME measures slant range, the minimum will be observed ...
Gerry's user avatar
  • 19.9k
1 vote

Why don't the Altitude-DME values in the approach profile match the Groundspeed-FPM values in the conversion table?

Have you ever seen a DME display show hundredths of a NM? To make the math work correctly, you will need to descend at 3.4498297885 NM on the DME. $$ \frac{2000-900}{372} X \frac{70}{60} = 3....
wbeard52's user avatar
  • 12.7k
1 vote

is DME groundspeed slightly inaccurate due to slant range?

Your slant range distance to the DME station is given by $s=\sqrt{s_g^2+a^2}$, where $s_g$ is the ground distance and $a$ is your altitude above the DME. Assuming you are in level flight, your ...
Chris's user avatar
  • 15.9k
1 vote
Accepted

How do you calculate the deviation from an RNAV waypoint radial?

To keep it simple and hide the trig here we can do it with vectors. Using your subscript nomenclature: Define Va as the vector from the VOR to the aircraft. (The VOR/DME gives this directly in polar ...
Jim's user avatar
  • 1,063
1 vote

How does a VOR or a VORDME affect the coding decision between CF or IF-TF respectively?

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 ...
Gerry's user avatar
  • 19.9k
1 vote

How is DME station ident coded in ARINC 429?

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 ...
sbabbi's user avatar
  • 345
1 vote

What button do I push on the instrument panel to activate DME in VOR navigation?

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 ...
Bianfable's user avatar
  • 55.9k

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