abbreviations, acronyms

[peterpan]

hello, i confused with abbreviations and acronyms in radio navigation menu.
default KSFO airport frequencies are as follows:
GND
TWR
ATIS
AWOS
NORCAL APP
NORCAL DEP
CLNC DEL
FSS-EFAS
CLASS C SOUTH
OAKLAND CLD
METRO OAKLAND INTL UNIC
please can you explain the meanings of these abbreviations/acronyms?
and which ones are navigation frequencies (VOR, ADF, DME, TACAN, or COM frequencies)
thankyou.

[Parnikkapore]

VOR,ADF,DME and TACAN beacons are navigation ones. COM = Communication ("Cleared to land, Delta Echo!")
In the C172, The top dails with two white needles are VOR/ILS and the bottom one with a yellow needle is ADF.

[eric]

COM

In a nutshell, listen to ATIS (automatic terminal information service) - it's an automatically generated message that tells you atmospheric pressure, winds, visibility, etc.

Then for departure, contact these COM channels using their corresponding frequencies:

* DEL (delivery) - request approval to fly to your destination and to start engines
* then GND (ground) for pushback and to taxi out
* then TWR (tower) to enter the runway and takeoff
* then DEP (departure) to leave the airport space

NAV

The VOR is for navigation. In the US they usually have a 130 mile range (depending on your altitude). They're usually located somewhere near the center of the airport. The VOR signal makes the vertical needle on your indicator go side to side.

The DME is also for navigation but for short range - like within 18 miles or so. It tells you if you're at the right altitude (and therefore right glide slope) for landing. The DME signal makes the horizontal needle on your indicator go up and down.

The airport VOR (the 130 mile range one) helps you find the airport. The runway VOR/DME combination (the short range one) helps you line up and land on the runway it's associated with.

ADF is a much simpler system than VOR. ADF is a simple AM radio signal and the needle on your indicator will point in the direction of the ADF beacon.

TACAN is a military (and more accurate) alternative to the VOR/DME setup. VORTAC is just a combination of VOR and TACAN.

A few resources...

Have a look at this for an explanation of the different Air Traffic Controllers (ATC) and what they're for:

https://www.vatsim.net/pilot-resource-c ... cd-gnd-twr

Have a listen to live communications from the various controllers so that it becomes something real to you and not just something to memorize:

https://www.liveatc.net/search/?icao=ksfo

[legoboyvdlp]

The DME is also for navigation but for short range - like within 18 miles or so. It tells you if you're at the right altitude (and therefore right glide slope) for landing. The DME signal makes the horizontal needle on your indicator go up and down.

I thought the DME was called distance measuring equipment because it measured distance?

[PINTO]

Yeah DME is for measuring distance, and definitely has a bigger range than 18nm. I think he's confusing it with a glideslope.

[eric]

Yeah that's right. The DME works by measuring distance. But it's function as a localizer is to use the distance measurement in combination with the plane's altitude to show if you're on the right glide slope.

I'm pretty sure about 18 miles being the signal distance. You can see the spec here on page 1-1-8, left column at the bottom of the page (or just search for "18 NM" and you'll see it:
https://www.faa.gov/air_traffic/publica ... -03-14.pdf

You can also see the localizer ranges on the FlightGear external map (the one that FlightGear opens in a browser). Once you have the map open, set it to show the navigation data. Zoom in to an airport that has ILS approach runways and click on the localizer. You'll see the range which is almost always 18 miles in the US. And of course as you fly you'll notice that you don't get a localizer signal lock until your within the range.

[tikibar]

The ILS consists of 2 and sometimes 3 pieces of equipment. There's the localizer, which provides lateral information (that's the "feather" you see on the ILS chart in the map view part). Then there's the glideslope, which provides vertical information in much the same fashion as the localizer. Some, but not all, ILS setups have a DME. On others, you have to rely on a separate VOR-DME or VORTAC to provide range information. In those cases, you'd have your Nav1 radio tuned to the ILS and Nav2 tuned to the VOR-DME/VORTAC.

The glide path is not calculated from the range information. It is defined by a pair of modulated radio signals from the glideslope station that are perfectly in phase when the receiver (the Nav radio on your aircraft) is on the correct glide path. This is way more precise than what you could get by calculating a glide path from the DME signal.

The 18 nm number is the reliable range of the localizer within 10 degrees of the localizer course. Within 10 nm, it is reliable to +/- 35 degrees.

[PINTO]

Glideslope =/= DME.

As tikibar said, there's a seperate glideslope station and a seperate DME station. DME only provides you with distance to the DME station, not glideslope information.

The 18nm range in your link is for a localizer, not for a DME.

DME's are often paired with VOR's, and can be reached much farther than 18nm. If you're flying using radio nav and only have one VOR/DME station nearby, DME's are instrumental in being able to find fixes (e.g. fix ABCDE is 50 miles out on radial 227).

A DME coupled to a LOC could maybe be reached 15-30nm out (usually farther than the LOC), but DME's coupled to VORs can be reached much farther, 150nm or so with a high altitude.

[eric]

Ok good to know - and thanks for the correction.