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| | |-+  ADF?? HELP PLEASE!!
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Author Topic: ADF?? HELP PLEASE!!  (Read 21906 times)
jdog4592
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« on: March 15, 2009, 09:16:05 AM »

For those of you who play FSX (Flight Simulator X) The ADF (Automatic,Direction,Finder) is an instrument i havnt quite figured out how to use or more importantly... what it does. If you can help me or show me a site that can that would be wonderful. im 16 and trying to prepare for a carrier of aviation.(probably US ARMY)
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KSYR-pjr
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« Reply #1 on: March 15, 2009, 11:34:47 AM »

The NDB (non directional beacon) is a ground-based navigational aid akin to a simple radio tower.  In other words, the tower transmits a "non-directional" radio signal, very similar to an AM radio station broadcast.  In fact, the ADF instrument on-board, which is used to point to an NDB, can also be used to tune AM radio stations.

For an excellent explanation of NDBs and ADF instruments, see here:  http://www.navfltsm.addr.com/howitbegan.htm

It is important to note that, at least here in the US, GPS is slowly taking over for all ground-based navigation (with the exception at this time of replacing existing ILS approaches).  The first casualty in this technological paradigm shift is the NDB/ADF, with VORs soon to follow.   The FAA has been decommissioning NDBs across the US at an accelerated pace.   Many aircraft these days are not even equipped with ADF instruments.

Therefore, in my opinion if I were you I would concentrate on understanding GPS rather than ADF, since the ADF will soon be totally extinct.
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Regards, Peter
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captray
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« Reply #2 on: March 15, 2009, 11:53:22 AM »

I don't play FSX but I am a pilot and instructor. So here goes; The ADF needle points to the station, it can be an AM radio station too. It does not account for wind drift. It will only let you home to the station. Homing is when you keep turning the airplane to keep the needle on the nose. You will eventually arrive at the station but it will be a circuitous route.
There is another instrument that some aircraft have, it's called an RMI (Radio Magnetic Indicator) what it does is that it puts the ADF needle on top of a DG (directional gyro) this was considered way cool when it first came out.
If you don't have a RMI then mentally you must put the ADF needle over the DG to get a picture of what is happening outside.
There are many tricks to keeping on course, but I will try to keep this simple. If you are headed towards the station (needle pointed forward) and you hold a constant heading, in no wind you will be spot on.
If the wind is from the left the needle will point left as you drift off course. To correct you need to turn into the wind (left) how far depends on how strong he wind is.
A good rule is double the degrees off course. So if you are 10 degrees right of course (wind pushing from the left) turn left 20 degrees. When the needle settles at 20 degrees right of course take out 10 degrees of correction and you should stay on course. The 10 left will be your wind correction.

Belive it or not I still have to do NDB approaches in the G4 as there are some that are not in the FMS database. It was and is a cheap reliable navigational aid.

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KSYR-pjr
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« Reply #3 on: March 15, 2009, 12:53:11 PM »

Belive it or not I still have to do NDB approaches in the G4 as there are some that are not in the FMS database.

NDB approaches here in the US or in other countries?  It seems from your avatar that you are all over the globe with that G4.
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captray
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« Reply #4 on: March 15, 2009, 01:30:23 PM »

Mostly Caribean, some in Canada and India. The FMS won't do anything that is a circle to land. Only does DME arcs and straight ins.
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jdog4592
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« Reply #5 on: March 15, 2009, 10:01:47 PM »

thx guys for the help I have trouble finding this information and thias site seems to help alot. from what im getting ADF is similar to NAV unit. the one where you tune in for ILS and things right. or more like VOR.
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captray
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« Reply #6 on: March 16, 2009, 06:09:48 AM »

Yes and no, more like a VOR however, unlike a VOR where you can tune in any radial. The NDB is non-directional. Hence the term Non Directional Beacon. You must decide what bearing you are on based on your DG.
Hope this helps, if not, ask away.....
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jdog4592
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« Reply #7 on: March 16, 2009, 06:21:31 AM »

I dont realy know what a DG is... among millions of other things lol. but ill keep it only to the big stuff that i cant figure out.
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thedude
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« Reply #8 on: March 16, 2009, 11:46:21 PM »

DG = Directional Gyro

It's similar to a compass but provides greater accuracy when flying headings due to the fact that it doesn't suffer from the magnetic dip that the compass does when turning / accelerating.

The DG is not always accurate though, and needs to be set to match the compass before takeoff, and the rule of thumb that I follow in flight is to set the DG to the compass heading every 30 minutes or so in straight and level flight.

The DG is what autopilots slave to when you select heading mode.
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jdog4592
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« Reply #9 on: March 17, 2009, 06:34:34 AM »

alright thanks... i guess i knew what directional gyro was but didnt comprehend it as DG.
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captray
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« Reply #10 on: March 17, 2009, 07:54:24 AM »

Sorry about that sometimes we get caught up in all the ABC's that we forget that there are others who have no idea what we are talking about.

Also, larger aircraft have a flux gate usually located in the wing or wings, that measures the lines of flux (the magnetic poles of the earth) and sets the DG for you. You only have to verify that it agrees with thbe runway heading before takeoff.
The smallest aircraft that I have flown with the above setup was a Piper Navajo. Twin piston engines.
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thedude
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« Reply #11 on: March 17, 2009, 09:46:29 AM »

I wish they would put that on the beech sports / 172's / 182's I fly!

Stupid big airplanes! lol

Now that you mention it though, I do remember that on the Cheyenne II I use to be able to sneak some time into with a buddy of mine.
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KSYR-pjr
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« Reply #12 on: March 17, 2009, 10:00:58 AM »

I wish they would put that on the beech sports / 172's / 182's I fly!

Those aircraft have a slaved HSI option (horizontal situation indicator, or a DG that combines a VOR-like directional indicator) that offers an HSI that automatically slaves to an onboard compass system, so no more precession and no more setting the DG.  Unfortunately, that option is/was a US $14,000 upgrade (with installation) so it is understandable that the aircraft owners opted for the standard DG.
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Regards, Peter
ATC Feed:  Syracuse (KSYR), NY
thedude
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« Reply #13 on: March 17, 2009, 10:16:30 AM »

Yeah we don't have that on any of our company airplanes.

Though the Cheyenne IA that we have here does have the slave option obviously.

The Sport and the Charger both have GNS 530 systems, and you can slave your VOR nav to the GPS, but unfortunately that's about the only thing you can slave.
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mstram
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« Reply #14 on: March 17, 2009, 12:06:09 PM »


Also, larger aircraft have a flux gate usually located in the wing or wings, that measures the lines of flux (the magnetic poles of the earth) and sets the DG for you. You only have to verify that it agrees with thbe runway heading before takeoff.

(In Johnny Carson voice), "I did not know that !"  Smiley

Reminds me of a dumb .. but fairly harmless error I made one night.  I was orbiting / "racetracking / sight seeing" around an area close to a controlled airport (yes I was in contact with ATC).  After about 1/2 hour I called the tower and said that I was ready to return to my home airport .. a direct path would take me across the controlled airport.  It was late at night, no traffic, so he cleared me across the airport, heading XXX.  I confirmed and rolled out on the heading.   After only less than about a minute, he called me and asked me to confirm the heading.  Yes, you guessed it, I hadn't reset the D.g. and it had drifted a good 10-20 degrees !.   I actually *had* noticed that the ground / buildings / etc, didn't quite "look right", just about exactly at the time he called.  Fairly embarrasing at the time Wink   Lesson learned though.

Mike
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