Dip Error
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I've never considered it... and normally get shot down when I attempt a tech explanation on pprune but here goes.
Imagine a beacon at a relative bearing of 045 ie 45 degrees to right of the nose.
The forward limb of the ADF antenna on the aircraft will receive a signal slightly phase advanced of the rearward limb(it's closer)! Similarly the right limb gets a signal phase advanced of the left limb.
The receiver resolves all this and points the needle to a RB of 045.
Now consider the extreme case of the same aircraft now at a 90degree bank angle.
Forward - aft signal reception unaffected.
Right - left signal reception now equidistant from transmitter. So equiphase!
No lateral component detected.
ADF needle will point RB= 000
Any advance on this?
Imagine a beacon at a relative bearing of 045 ie 45 degrees to right of the nose.
The forward limb of the ADF antenna on the aircraft will receive a signal slightly phase advanced of the rearward limb(it's closer)! Similarly the right limb gets a signal phase advanced of the left limb.
The receiver resolves all this and points the needle to a RB of 045.
Now consider the extreme case of the same aircraft now at a 90degree bank angle.
Forward - aft signal reception unaffected.
Right - left signal reception now equidistant from transmitter. So equiphase!
No lateral component detected.
ADF needle will point RB= 000
Any advance on this?
Guest
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This would generally be true for the "old" style loop antennas used on, for example, DC-4's. NOT true for new style antennas. Also "dip error" is generally considered to apply to inflated ego F/O's at EK (altho they do not collectivly know of the condition as yet) 
)
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I was confused about dip error as well so I e-mailed Bendix/King who make the KA44 antenna which is fitted to vast numbers of single and twin pistons. They tell me that the dipping of the needle towards the low wing is caused by a shielding effect in the antenna which uses a set of coils in an X shape plus a single coil across the fore-aft axis of the aircraft (Bellini-Tossi system???). Strangely enough older antenna systems are not affected by dip error so, if you've got an old 'towel rail' type antenna, you'll be OK. Even on large aircraft, some suffer from dip and some don't - the RAF's C-130s do, the Canberra doesn't, the DC-10 doesn't.
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I would have thought the situation a good deal simpler than indicated above.
The effect is apparent on all the ADFs I've used from the Bendix as fitted to the DC-4 to the 747-400. Re the comment on towel rail antennae, they are the sense element and don't affect the outcome.
The ADF loop is intended to track only the direction of the beacon signal in respect to the horizontal plane. (no pun) If you've used a wire-wound rotating-loop aerial in sky wave you'll know why Bellini-Tosi, Marconi-Adcock or their successor fixed loops have been in vogue since the days of MF ranges.
While later ADFs perform better (one would hope so) their horizontal reception is still relative to the airframe. I am unaware of an ADF with attitude input, but stand to be corrected. Therefore if the aircraft banks, the ADF receiver tilts.
If you were overhead a station with 90 degrees of bank, the ADF would see the beacon straight down, at right angles, and the needle therefore at 090 or 270. The effect is less, but still there at varying degrees (pardon, no pun) dependent on height, distance and angle of bank.
The effect is regularly seen when turning inbound in a holding pattern, and a pilot who has been watching what he thinks is a good turn onto inbound track, finds the needle does a dart to indicate off track as he/she rolls the wings level.
Trying to anticipate is possible, but due to the variables, it is not easy. The solution is to fly (a) in LNAV, or (b) the turns and outbound leg on DR as accurately as you can. Roll out on to inbound heading promptly, let the ADF settle and correct immediately for track error.
The effect is apparent on all the ADFs I've used from the Bendix as fitted to the DC-4 to the 747-400. Re the comment on towel rail antennae, they are the sense element and don't affect the outcome.
The ADF loop is intended to track only the direction of the beacon signal in respect to the horizontal plane. (no pun) If you've used a wire-wound rotating-loop aerial in sky wave you'll know why Bellini-Tosi, Marconi-Adcock or their successor fixed loops have been in vogue since the days of MF ranges.
While later ADFs perform better (one would hope so) their horizontal reception is still relative to the airframe. I am unaware of an ADF with attitude input, but stand to be corrected. Therefore if the aircraft banks, the ADF receiver tilts.
If you were overhead a station with 90 degrees of bank, the ADF would see the beacon straight down, at right angles, and the needle therefore at 090 or 270. The effect is less, but still there at varying degrees (pardon, no pun) dependent on height, distance and angle of bank.
The effect is regularly seen when turning inbound in a holding pattern, and a pilot who has been watching what he thinks is a good turn onto inbound track, finds the needle does a dart to indicate off track as he/she rolls the wings level.
Trying to anticipate is possible, but due to the variables, it is not easy. The solution is to fly (a) in LNAV, or (b) the turns and outbound leg on DR as accurately as you can. Roll out on to inbound heading promptly, let the ADF settle and correct immediately for track error.
