40

How is TACAN different from the VHF Omnidirectional Range (VOR) system? A very short question, but the answer calls for describing several techniques which are by themselves difficult to summarize without taking liberties with reality, so the post is rather long and should be read by sections of interest rather than totally at once. And for those not ...


32

Aircraft carriers use a TACAN, which stands for Tactical Aid to Navigation. (The Navy is really good at making acronyms that don't follow normal conventions for abbreviation) Functionally the TACAN is like a VOR with DME, providing bearing to and from the ship, as well as range. The system is not susceptible to rocking motion, and least not perceptibly. (...


25

In short The night effect is actually a mirage. Listening to radio communications originating from below the radio horizon is like looking at a looming: Looming optical illusion, source: SKYbrary Both are strange things, unless we force ourselves to take into account electromagnetic waves (including light) don't travel in straight line but are subject to ...


19

A radial is always pointing (radiating) away from the VOR. But your instrument shows the TO/FROM indicator as TO. So you are crossing a 210 course towards the VOR, which means you are on the 030 radial from the VOR. What does it mean to be crossing a radial? This just refers to the fact that you cannot determine your heading (or track) from the CDI. Based ...


17

Totally legal to tune it up & use it. If it is a VORTAC, it will work just like every other VORTAC out there. If it is a TACAN, you may be able to get DME from it, but you won”t get bearing from it without a TACAN receiver. Many, perhaps most VOR’s out there are in fact VORTAC’s — the TACAN station is colocated with the VOR. It is possible to have a VOR-...


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 ...


14

Yes, without a shadow of a doubt. Many airports now publish GNSS (Generic term for all types of satellite navigation) approaches, completly negating the need for those aids even during complex, critical phases such as approach and landing and take off and departure. Modern GNSS systems are capable of utilising synthetic VORs where even when doing something ...


12

As pointed out in the comments, I think you have things turned around. If you select the frequency of a VOR that has a co-located DME, the system will automatically also select the DME frequency. Thus, I'm guessing that what you perhaps meant to ask is under what conditions do you manually tune the DME frequency. If that is NOT what you are asking, put a ...


12

Yes, it is true. This FAA page has more info. The Very High Frequency Omni-directional Range (VOR) Minimum Operational Network (MON) provides a conventional navigation backup service in the event of a loss of Global Positioning System (GPS) signal. The MON includes the minimum number of geographically situated VORs in the contiguous United States (CONUS) ...


12

You are correct, the time difference generates hyperboloids in 3D space and as such can be used to find the 3D position. However, if the transmitters are far apart and/or in the same plane, the geometry of the intersecting hyperboloids is such that the accuracy in the vertical axis is very poor. When the receiver is in the same horizontal plane as the ...


12

As the name indicates, this automatically centers the CDI needle, by selecting the appropriate TO radial. From the manufacturer of INS 422, an integrated navigation system including a VOR: Pushing the remote automatic radial centering button enables circuitry to automatically position the digital CDI indication to provide a one-time radial "TO" ...


11

The value +/-40° is correct, but need to be interpreted. The primary reason of the existence of a "silence" (confusion) cone is a design choice to increase navaid range. Range and "isotropy" are antagonistic. However, when the aircraft approaches the confusion cone, say at 45° elevation, while flying at 9 km above the station, its slant ...


11

Source: FAA 6750.16E - Siting Criteria for Instrument Landing Systems The more common G/S antenna type works by reflecting the signal off flat ground, called "image type". A non-image type was not available in the 70s as it's a mid-90s invention (patent; IEEE).


11

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 same-frequency stations must be considerably distant. The result, in normal conditions, is the receiver cannot switch uninterrupted from the current station to a ...


11

The reason is, that for a VOR, the receiver in the aircraft determines the radial based on calculating the phase shift and as the VOR is oriented to the magnetic north of its location, we need the variation of the station. Think of it as a lighthouse which changes the color through a full turn and hence you can just tell by the color, which radial you are on....


10

Isn't it too much? No, it isn't. VOR's and NDB's are pretty old technology. VOR's were introduced in the 1930's and 40's, but are still commonly used today. If you have a cone of confusion of 45 degrees to all sides, this means that, at 40.000 feet, the signals will be unreliable within about 6 miles from the beacon - which isn't really that much. At lower ...


10

Civilian aircraft can use part of TACAN, the Distance Measuring Equipment (DME) signal is the same as civilian DME. As for the directional component one big reason is that the military don't want you to. Even if the military didn't mind there would likely be no demand as the costs of using TACANs outweigh the benefits. TACAN is essentially a more accurate ...


10

You wrote that intuitively, one would expect that UHF-radio-wave-reflecting surfaces near your glideslope antenna would be a bad thing, due to the potential for multipath interference However, multipath interference is exacly what we want here. The antenna is mounted a certain height above ground and the aircraft receives both the "line of sight" and "...


7

Your question presumes that a "fast align" can be performed instead of a "full align", but is in some way deficient. But this is not the actual usage. Starting from cold (unpowered), the IRS must always go through a full alignment to find true north, a process which takes about 7 minutes. The IRS is also manually given an initial position, usually via the ...


7

En-route marker beacons are close relatives of the outer/middle/inner markers used on ILS approaches. Airway markers use the same audio frequency as inner markers, and some older equipment has indicators for airway/outer/middle. Older versions of the FAA AIM discuss marker beacons, but later versions omit them. From Wikipedia: From the 1930s until the 1950s,...


7

Absolutely. A VORTAC is nothing more than a VOR colocated with a TACAN. Most VOR-DMEs in the US are VORTACs. If there happens to be one located on a base you are certainly still able to use it.


7

Seattle’s "golf ball" in Discovery Park was once part of the country’s Nike Hercules air defense system of missiles and radars in the 1950s. While most of the structures have been torn down, this golf ball still stands as a relic of the Cold War. Discovery Park used to have an array of radars at its peak. It was a Nike Ajax air defense site in 1953 ...


7

Yes, "D" is correct. A picture is worth a thousand words......


7

In VOR early days, the 40s, the stable phase locked loop frequency generator was not available. A common frequency reference was the very stable public AC power grid frequency. The angular velocity of a synchronous motor is locked on the power source frequency, such motor can be used to actuate a variable resistor or capacitor to generate a stable wave which ...


7

It depends on your instrument suite. If you have just a radio with connected HSI, you have to set the course yourself, because on the radio you only set the frequency and there are hundreds ILS installations with the same frequency across the world. If you have flight management system with a waypoint database where you set the ILS by its identifier, it will ...


6

The category specs are easily found on Wikipedia. Here is a concise view of the ILS approach minimums, as far as the crew is concerned. Cat I DH: 200 ft (61 m) or more RVR: 1,800 ft (550 m); at some airports 1,210 ft (370 m) is approved. For single crew operations, increased to 2,600 ft (790 m) orVISIBILITY 800 m (2,600 ft) Cat II ...


6

Yes, it is commonly used, especially in large complex airspaces. If two VHF direction finders are installed at sufficient distance from each other, they allow the ATC system to triangulate the position of a VHF transmission. This position is then indicated on the air taffic situation display, which helps the air traffic controller to quickly correlate the ...


6

I guess it depends on what you consider to be a "high level of integrity and safety." VOR is a perfectly acceptable means of navigation if you know how to use it. And, I guess, if the transmitter hasn't been flooded. Let's take a look at the data for the Las Vegas VOR: Now, that does look like a lot of "unusable" radials, but it's not actually as bad as ...


6

Once you select and tune NAV 1 or NAV 2 (assuming the NAV 1 or NAV 2 Navaid has associated DME) and then select the "Hold" mode the DME will stay on that frequency after you change the NAV 1 or NAV 2 to another frequency. Note that the DME hold mode is only associated with NAV 1 and NAV 2. The RNAV and GPS interface with the 400 DME unit would ...


5

Well, the short answer is that it operates in the same way as VOR except it uses UHF instead of VHF - and is therefore less subject to distortion - and always incorporates DME so a range and bearing are both given. VOR/DME is the civilian equivalent.


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