View Full Version : NDB approach

4th Dec 2006, 19:57
I've noticed that in a lot of threads they talk about at job selections they get in the simulator and perform a take off and an NDB approach. could someone please explain to me what is an NDB approach?

Malcolm G O Payne
4th Dec 2006, 20:57
NDB stands for Non-Directional Beacon and an NDB approach is one based on the use of ADF (Automatic Direction Finding) equipment fitted in the aircaft that gives the relative bearing of the beacon. It is a non-precision approach, has limitations and is usually found at minor airports, although some major airports still have them. Due allowance must be made for signal limitations, especially when there is thunderstorm activity. As far as the airport operator is concerned they have a cost advantage as they do not need to be calibration tested, as is the case with ILS (Instrument Landing System) approaches. I could go on, but I hope this gives an outline.

5th Dec 2006, 10:22
Basically you use the NDB to get to a certain point and from then on the approach is made with visual reference from that point or in otherwords a visual approach is made, subject to minimum visual references.

5th Dec 2006, 11:23
I'd just like to add that by putting candidates through a session where they must demonstrate an NDB approach to land the examiner/assessor can get a good idea of a pilot's flying skills. A lot of NDB's dotted around the UK date back to the WW2 era. They are therefore unreliable and difficult to master when compared to modern, safer VOR or GPS signals especially for the approach to land - hence the reason for using them to test people!

What you must remember is that the receiving station, an ADF instrument points to the location of an NDB relative to you, and not strictly speaking, where 'to fly to' as is the case with other instruments.

So if winds and gusts are thrown in, you will no doubt be assuming a heading to correct for that wind (think visually for a minute). In this situation the needle on the ADF will be pointing somewhat to the left or right of your heading with the difference being Your Heading Minus the Relative Bearing. So you can see that the ADF instrument doesn't always give you a direction to turn to in order to fly over a beacon in addition to that you must factor in the wind into any NDB tacking. Therefore a candidate is also tested for his/her ability to judge and make the appropriate corrections/ignorations(:}) for the wind which in all truth and reality can never be known with certainty.

low n' slow
5th Dec 2006, 11:43
To sum it up, they're a lot of fun.
I enjoy them but I know of many that don't...


5th Dec 2006, 20:03
Speaking as someone who is learning to fly NDB approaches at the moment, I think they are an excellent training aid and without doubt increase your piloting skills. If you can fly an NDB approach accurately, you'll fly a VOR or VOR/DME without any problems.

In the real world though, I would hate to have to use an NDB to land in weather close to approach minima. Perhaps it is just in the PA28.. but I find that even with the needle sitting right where it should be, you tend to end up significantly off the centre line. The ones around my part of the world really deserve the title "non-precision"!!

6th Dec 2006, 00:01
You said it veetwo...

NDB's, either in en route nav or in approach situations can sometimes be dangerously inaccurate, especially if subjected to shoreline, night time or mountain effects. Tracking to an NDB without some kind of DME (or GPS readout) fix can also make life tough, seeing that the needle gets unreliable within about 2nm of the beacon.

There is a particular airport on the west coast of British Columbia which has a reputation for being a not very nice place to fly the approach into, particularly at night near mins. IMHO, NDB's should be outlawed in some locations due to their flaws. Its all good and dandy in nice flat, no terrain or shoreline locations, but try it elsewhere and it can give you that sickening feeling as you arrive at your MDA and the needle is jumping all over the place...:=

6th Dec 2006, 14:38
Any expected NDB approach with wx giving close to minima, should and is looked at very carefully by any airline pilot.
Some airlines even mandate that a report is filed after EVERY non precision/NDB approach is completed.

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