Tracking NDBs!!!

[magneticflip1]

Hi guys,

Im having a few problems with NDBs!! I understand how to track them and the principles etc, however I'm having difficulty deciding whether to add or subtract 90 degrees to the track QDM (for a 90 degree intercept) before then turning onto the QDM.

Are there any tips or visualisation techniques using the DI or ADF that saves brain power and time??

Many thanks!!

[Keygrip]

Try the freebie download demo of RANT2000.

Here (http://www.oddsoft.co.uk)

[magneticflip1]

I already have a demo of RANT thanks!!! Does anyone have any tips though, I could try on RANT?

[Keygrip]

Well, that really depends on just what your problem is.

If, as i understand it, you have trouble intercepting nominated magnetic tracks - there is a complete section of it on the RANT disk.

There is a tutorial section that tells you how to do it - and then endless numbers of randomly generated exercises for you to practice (either with the aircraft in view for you to have a think - or without it, for you to have a harder think).

[yawningdog]

Perhaps I don't understand your querey, but if you are trying to fly at right angles to your required QDM to the NDB, adding or subtracting 90 degrees will depend upon from where you are approaching the intercept.

For me the main thing with NDB useage is keep a visual picture using the DI & RBI together. If the RBI is saying down to the left, look down to the left on the DI, there's the QDM.

When you know your present QDM, you can visualise where you need to go to find your proposed QDM intercept.

[Gerund]

You have worked out the QDM you are on and the one you want, so I imagine you have no problem with that.

A good rule of thumb with a QDM is to turn the opposite way to the QDM you want. eg you are on 330 and want 020, the opposite way is back past 330. So, for the 90 degree intercept you are asking about, the intercept heading required, is 020 - 90 = 290 degrees. If you wanted to intecept a QDM of 310 at 90 degrees, turn opposite way, ie 310 + 90 = 040. You can step this down as required. (Visualise it as the QDM you are on as being between the QDM required and the intercept heading required - works either way).

You don't ask about QDRs but for completeness, the technique is similar. Work out the QDR you are on, and this time turn further past the QDR required. eg on a QDR of 360, want 040, at an intercept of 30 degrees, turn past 040 by 30 degrees, ie 070. Or intercept of 90 degrees, then 130 degrees etc. Again, works either way.

To get this fixed in your mind, draw a compass rose on a piece of paper and try out the above with various scenarios.

Fortunately NDBs are being phased out. Very soon the only good thing about the ADF will be to listen to the music!!

There are as many methods as types of coffee, but I hope the above helps. Good luck!

[High Wing Drifter]

Fortunately NDBs are being phased out. Very soon the only good thing about the ADF will be to listen to the music!!
Really? There is no reliable civil GPS system to replace them though. Even the US halted its decomissioning when it reaslied all is not well in GPS land.

[Tinstaafl]

WTF is a 'QDM'? Bearing to the station? Bearing from the station?

Are you using a fixed card or RMI?

For an intercept at 90 deg (your specific question but it works for other angles). Bit hard to describe without diagrams...

Step 1. Work out where you are. It's easier using an RMI but can be done using a fixed card + the DI.

For all my references to the RMI (if you're using an RBI + DI) you should mentally transpose the position of the needle onto the DI. Count the number of divisions (the 10 deg & 5 deg marks on the compass rose) the head or tail of the needle is L or R of the nose/tail. Note the same number of divisions in the same direction on the DI. That's What the RMI is doing for you. Use your pencil by moving it from the RBI to the DI if you have trouble imagining it.

On the RMI (or RBI transposed to the DI) the centre of the insrument represents the navaid. The tip of the tail of the needle represents the a/c. A/c heading is always oriented so that it points 'up' the instrument panel.

Whatever bearing is under the tail of the needle is the a/c's position relative to the aid. You will also be able to see if the navaid is behind or in front of you as well as to the L or R.

2. Note the bearing FROM the station you wish to intercept. Mentally picture this line on the RMI (or DI). This it the track you wish to intercept. If it's a bearing TO the station then after you find this postion, look at the opposite side of the RMI ie the reciprocal.

3. Compare where you are (the tail of the needle) to the the desired track to intercept. If the desired track is somewhere to the R, turn R so that the desired track at the 90 deg mark on the RMI/DI. If left then turn Left.

4. You will be on track when the head of the needle moves to 90 deg.


NOTE: This method can be extended to use any intercept angle you like AND you can use it to get an approximate intercept heading to track from a given postion on a bearing to another bearing/distance eg tracking in to the station at a certain distance (say 10 or 20nm), cut the corner to intercept a track outbound at a given distance (say 20 or 10 miles or whatever).

[FlyingForFun]

As a new IMC pilot, not sure I'm qualified to answer, but I'll give it a go anyway...

Sounds like the problem is your situational awareness. If you know where you are, what direction you're going, and where you want to go to, and can draw those things on a chart without thinking about them (you don't actually need to draw them on a chart, just be capable of doing it if required) then it should be obvious whether you need to turn left or right.

To me, figuring out where I am is much easier than remembering lots of rules and equations about how much to turn and in which direction. Also, this then works whatever nav-aids you're using, it's not NDB-specific.

FFF
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[IO540-C4D5D]

Gerund

Do you have a reference for phasing out of NDBs? Here in the UK they are used almost entirely only as beacons in IAPs - you fly over the top of them and after the beacon you maintain the outbound "radial" for a bit before doing the inbound turn. They can also be used for holds - much loved by IMC/IR instructors but rarely if ever actually used for that. They are not used for en-route navigation; VORs do that and there is no sign of those being phased out.

FFF

I think you are absolutely right - situational awareness is what's needed and that comes together after a while. I think most of the visualisation aids are more trouble than they are worth.

[Keef]

IO540 - sadly, there is a proposal to phase out VORs - by something like 2014. The plan is to go to DME/DME and GPS, presumably linked with the ADS-B equipment that we will all have to carry.

Note ADS-B, not Mode S. The inference (not stated clearly anywhere) is that we'll all have to buy Mode S kit by 2008, then throw it away and go to ADS-B a few years later.

[IO540-C4D5D]

Keef

OK, DME-DME fixing makes sense, it is the most accurate of ground based navaids anyway. But we then have to buy yet more kit... is there anything for GA which gives a moving map, driven by GPS with a DME-DME fallback? The airliner systems have that I believe. Technically it is trivial to do once you have the map database to start with so you know which DME to ping.

This sort of thing could be done with an add-on DME-DME box; all it has to do is emit an NMEA data stream and one can drive an MFD with that... Fit a switch on the MFD input so it can be fed off either a GPS or a DME-DME.

[eyeinthesky]

Not strictly relevant to the question posed, but one of the best pieces of advice I was ever given with regards to NDB tracking was this:

No matter how long you wait, the head of the needle will NEVER go back UP the dial on its own. You HAVE to get the nose of the aircraft the other side of it and PUSH it back to where you want it.

Conversely, the tail of the needle must be PULLED into the postion you want it.

If you visualise what these sentences are saying it all becomes clear.

[Evil J]

Don't know if this will help but what helped me understand NDB's was to think of them as VOR's, only you have to turn the whole aircraft not just the OBS ring!! Works for me!!

[dirkdj]

Magneticflip,

here is how you can visualize it on the DG/HSI:

consider the center of the instrument with the airplane symbol to be the NDB station, if you work in QDM, the bearings are TO the station, so draw a mental line towards the middle of the instrument.

Lets suppose you are on a QDM of 270, with a heading of approximately 270 (+- wind correction). In this case the current QDM lies from the bottom of the instrument straight up towards the center, pointing towards 270. (draw it on paper if not in the airplane).

So, if you have to intercept at 90 degrees for example QDM300, first visualise where QDM300 is situated, draw a mental line on the DG from 120 to 300 degrees, stopping in the center.

It is evident that the required QDM is to the left and that you have to subtract 90 degrees from the required QDM (300-90=210) to intercept it.

Fly a heading of 210 for some time.

When the ADF needle will be on your right hand wingtip, then you are established on the QDM300.

In practice, you would start to roll out of the 90 degree intercept about 10 degrees before (at 080 degrees, 10 degrees before the right wingtip).

Following the same visualisation method, try to work out how to intercept a QDR?

I hope this helps. The difficulty for a newcomer is that you have to mix different angles: heading, bearing to the station, ADF needle versus aircraft nose.

I recommend a PC IFR flight simulator for properly learning these things. I use Jeppesen Flite-pro for keeping current on procedures. I recently discovered x-plane (www.x-plane.com) as a very fine simulator with excellent flight dynamics. My favorite is the C119, or the PC-9.

Dirk

[Keef]

I think the real answer to the question is "you need to learn situational awareness" so that when you look at the ADF needle, it tells you where you are. Then you need to be aware of what to do to correct that, if it's not where you want to be." I spent many happy hours poling a Warrior round Florida learning that.

For me, the most important single skill with the ADF is remembering and using the + and - sectors of the display. If I am off track, I turn in the right direction and recite (for example) "steering plus 20 waiting for minus 20". When the DI shows 20 degrees "plus" and the ADF 20 degrees "minus", I'm back on track. It works!

I practice that often using MSFS - which is quite good for that. Set up a stiff wind, with different directions at different heights, and then try to track out and in on an NDB.

And recognise that ADF is not very accurate! On my IR checkride, I did a theoretically perfect NDB procedure at Fort Myers. I stopped at MDA and asked the examiner to "decide". He had me continue for a while, then we went around. He asked me how far I was from the centreline - I said "the instruments say I was exactly on it". He said "Yes, they did, and you were actually a good half mile off."

I passed. Fort Myers is near the coast; the US teaching on NDBs doesn't cover coastal effect. No idea if the two are connected, but it seems likely.