ADF dip
Join Date: Mar 2000
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For some bizarre reason you have to track the inbound QDM within 5 degrees on a non-precesion approach for the IRT, often this is done asymetrically as well just for a laugh! For best enjoyment do your IRT on a really buffety day with lots of windshear and enjoy the challenge of keeping that little needle within the tolerances.
On a simulation note I bought Jeppersen FlitePro which dissappointingly has no ADF dip. I recently contacted them and asked them if they were likely to include it on a later release, the answer NO!
On a simulation note I bought Jeppersen FlitePro which dissappointingly has no ADF dip. I recently contacted them and asked them if they were likely to include it on a later release, the answer NO!
MJR - what's bizarre about having to track within 5 degrees? If you were doing it for real wouldn't you want to be on track?
5 degrees is the tolerance required for the IRT. Examiners have discretion and whereas you might stray outside the tolerance and pass, you can also stay within the tolerance and fail!
E.g. on a good day in perfect conditions if a candidate made no attempt whatsoever to correct a 5 degree error one might consider a fail. In other circumstances, weather/crew workload etc. a candidate might stray outside the tolerance but you would be happy to pass him. Essentially the examiner would have to ask himself whether he might have done the same thing in the circumstances.
Pilots sometimes refer to "limits" which is not the correct terminology - they are "tolerances" but essentially it all boils down to the same thing in the sense that the "professional" pilot is the one who is striving to fly the procedure accurately at all times.
5 degrees is the tolerance required for the IRT. Examiners have discretion and whereas you might stray outside the tolerance and pass, you can also stay within the tolerance and fail!
E.g. on a good day in perfect conditions if a candidate made no attempt whatsoever to correct a 5 degree error one might consider a fail. In other circumstances, weather/crew workload etc. a candidate might stray outside the tolerance but you would be happy to pass him. Essentially the examiner would have to ask himself whether he might have done the same thing in the circumstances.
Pilots sometimes refer to "limits" which is not the correct terminology - they are "tolerances" but essentially it all boils down to the same thing in the sense that the "professional" pilot is the one who is striving to fly the procedure accurately at all times.
I have had to perform 27 ADF only approaches in the UK in the last 3 months in a Boeing 737 on scheduled ops. 3 of those were to minimums and one resulted in a go-around.
Dip is present in my aircraft type to about 7 degrees. The years spent in various holds teaching Dip to students allows me to somewhat enjot these approaches without any aprehension.
If you can hold and approach to minima on and NDB then you can do most things. A non-precision night circle to land on one engine not withstanding...
WWW
Dip is present in my aircraft type to about 7 degrees. The years spent in various holds teaching Dip to students allows me to somewhat enjot these approaches without any aprehension.
If you can hold and approach to minima on and NDB then you can do most things. A non-precision night circle to land on one engine not withstanding...
WWW
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Triple W:
It is interesting that you are getting the privilege to do ADF approaches in Boeings neat jet.
The ADF approach was for years the only approach we used in the Arctic, one gets so used to them you never really think of the physics of why the needle does what it does you just fly the thing and experience allows you to recognize when something is really out of whack.
The secret of course is to always be aware of where you are and where the fu##ing thing is headed. If any doubt exists that is what the missed approach is for.
By the way I don't know if you have used the ADF in mountinous regions, it can really get goofy way down in deep valleys, but the D.I dosen't know you are in a valley.
Hmmm a 737 doing ADF's must be fun?
.............
The hardest thing about flying is knowing when to say no.
It is interesting that you are getting the privilege to do ADF approaches in Boeings neat jet.
The ADF approach was for years the only approach we used in the Arctic, one gets so used to them you never really think of the physics of why the needle does what it does you just fly the thing and experience allows you to recognize when something is really out of whack.
The secret of course is to always be aware of where you are and where the fu##ing thing is headed. If any doubt exists that is what the missed approach is for.
By the way I don't know if you have used the ADF in mountinous regions, it can really get goofy way down in deep valleys, but the D.I dosen't know you are in a valley.
Hmmm a 737 doing ADF's must be fun?
.............
The hardest thing about flying is knowing when to say no.
Join Date: Jul 2003
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Dip seems to have something to do with the poor location of antenne.
We had a fleet of PA28's.
The one which produced no dip had its loop aerial mounted half way up the tail instead of between the wings.
Logic would suggest the wings shield the aerial during turns thus producing errors. Errors being seen to be greater on multi's.
We had a fleet of PA28's.
The one which produced no dip had its loop aerial mounted half way up the tail instead of between the wings.
Logic would suggest the wings shield the aerial during turns thus producing errors. Errors being seen to be greater on multi's.
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No-one has mentioned the fact that an NDB on an airfield (Half-a-crown a week maintainance) is an invaluable aid to keep positional awarness when under radar vectors, and I have had occasions when radar has "forgotten" me!
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Lifted direct from AP3456:
14. Bank Error. When an aircraft is banked, the aerial is tilted and some of the signal is detected by the horizontal elements of the aerial. This will produce an error in the ADF bearing until the wings are levelled again.
It's a bit like bank error in a magnetic compass. The needle, in this case the aerial, moves relative to the thing it's pointing at and moves to re-acquire it. Relative bearings of 360, 090, 180 and 270 provide the least errors (not to be confused with Quadrantal Error).
14. Bank Error. When an aircraft is banked, the aerial is tilted and some of the signal is detected by the horizontal elements of the aerial. This will produce an error in the ADF bearing until the wings are levelled again.
It's a bit like bank error in a magnetic compass. The needle, in this case the aerial, moves relative to the thing it's pointing at and moves to re-acquire it. Relative bearings of 360, 090, 180 and 270 provide the least errors (not to be confused with Quadrantal Error).
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Jessfix,
Thom 5 has a tiny paragraph on 'dip' but calls it "Turning Error" and defines as the loop taking time to resolve the signal.
BGS notes define dip as being something related to some Bendix King installations and is at its maximum with relative bearings +/- 45 and 135 deg.
RANT defines ADF dip as when the sense antenna shields the loop antenna. Says dip error reduces eventually to zero as the beacon moves abeam.
Take your pick. Guesstimating 10 degress with a rate 1 turn seems to work well enough every time.
I recall reading somewhere, that some Bendix King installations have been modified to remove the problem.
Thom 5 has a tiny paragraph on 'dip' but calls it "Turning Error" and defines as the loop taking time to resolve the signal.
BGS notes define dip as being something related to some Bendix King installations and is at its maximum with relative bearings +/- 45 and 135 deg.
RANT defines ADF dip as when the sense antenna shields the loop antenna. Says dip error reduces eventually to zero as the beacon moves abeam.
Take your pick. Guesstimating 10 degress with a rate 1 turn seems to work well enough every time.
I recall reading somewhere, that some Bendix King installations have been modified to remove the problem.
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The best way to fly ADF is to;
not read the instrument unless wings are level. You should be targetting a heading anyway.
not to read read any moving instrument.
Big End Bob, I have noticed the same, In particular,high wing aircraft seem to suffer less from dip.
Tracking within 5degrees is very relevant in some of the valleys in Canada where I started my flying. If you try to be within 5deg and get 10deg then not good but OK, but if your limits are 10deg you will get 20deg etc.
ADF is a good instrument because it always shows you where the station is pictorially.
Imagine you are a little aeroplane on a pivot on the tail of the needle always pointing vertically up the instrument panel. The beacon is always in the centre of the instrument.
Just turn in the direction that will push or pull the needle where you want it to go.
Remember also that the needle head always wants to move towards the wind.
I believe that single needle tracking is a good and satisfying skill to posess for situational awareness.
not read the instrument unless wings are level. You should be targetting a heading anyway.
not to read read any moving instrument.
Big End Bob, I have noticed the same, In particular,high wing aircraft seem to suffer less from dip.
Tracking within 5degrees is very relevant in some of the valleys in Canada where I started my flying. If you try to be within 5deg and get 10deg then not good but OK, but if your limits are 10deg you will get 20deg etc.
ADF is a good instrument because it always shows you where the station is pictorially.
Imagine you are a little aeroplane on a pivot on the tail of the needle always pointing vertically up the instrument panel. The beacon is always in the centre of the instrument.
Just turn in the direction that will push or pull the needle where you want it to go.
Remember also that the needle head always wants to move towards the wind.
I believe that single needle tracking is a good and satisfying skill to posess for situational awareness.
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This is a bit sureal, but imagine the ADF needle is connected via a piece of elastic to the NDB beacon.
When you bank, as in the hold, the elastic gets caught on the wing tip producing error.
When you roll level the elastic becomes taught again giving a true bearing.
When you bank, as in the hold, the elastic gets caught on the wing tip producing error.
When you roll level the elastic becomes taught again giving a true bearing.
Gizajob
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I asked a similar question on dip in Tech Log a little while ago - will see if I can find it... Had some good explanations.
Found it - http://www.pprune.org/forums/showthread.php?t=234057 See especially post #4 from Dan Winterland - neat explanation that worked for me.
The search button is your friend, as Jerricho would say...
Found it - http://www.pprune.org/forums/showthread.php?t=234057 See especially post #4 from Dan Winterland - neat explanation that worked for me.
The search button is your friend, as Jerricho would say...
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To counter it, anticipate by lagging your roll out a bit . I'm sure someone more clever than I could work out how much lag would be necessary depending on the cosine of the angle of bank, but I was taught to use th TLAR method. (That Looks About Right). It is a function of the angle of bank, regardless of aircraft type.
Blimey, this is a blast from the past! I seem to remember first posting on this topic in 2001. Since then, I've moved on for instructing and flying classic jets to flying Airbus wonderjets where all you have to do to fly a NPA is press the Approach button and sit there arms folded while the kit does it all until MDA when you press the red button and land it.
But as far as I remember, at GA aircraft speeds of about 90 to 120 knots, I used to reach anticpate by about 2 degrees and for airliners about 5 degrees. This means you start to roll out when the needle has either 2 or 5 degrees before it reads the approach course.
But this theory relies heavily on the TLAR premise. (That Looks About Right). Hope this helps.
But as far as I remember, at GA aircraft speeds of about 90 to 120 knots, I used to reach anticpate by about 2 degrees and for airliners about 5 degrees. This means you start to roll out when the needle has either 2 or 5 degrees before it reads the approach course.
But this theory relies heavily on the TLAR premise. (That Looks About Right). Hope this helps.
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Has anyone mentioned ADF lag yet ? I fly GA aircraft at the speeds DanW mentioned and the ADF needle typically lags some 15 degrees behind the DG for it to be spot on coming out of a base turn into the final approach. If they were running neck to neck then you're undershooting.
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not read the instrument unless wings are level. You should be targetting a heading anyway.
not to read read any moving instrument.
Good advice Pilotbear - look at the needle and decide what heading you need to turn to then ignore the dip during the turn (if you add or subtract your drift to that heading even better).
not to read read any moving instrument.
Good advice Pilotbear - look at the needle and decide what heading you need to turn to then ignore the dip during the turn (if you add or subtract your drift to that heading even better).
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Every aircraft i have flown the adf reacts differently.
We had one warrior where the adf loop was mounted between wing and tail.
Never suffered any errors.
So why aren't all adf loops fitted on the rear fuselage?
We had one warrior where the adf loop was mounted between wing and tail.
Never suffered any errors.
So why aren't all adf loops fitted on the rear fuselage?
