Compass Swing

Thanks Gents,

In short; The adjustments are for electrical/ferrus interference within the aircraft, that may affect the compass, as the aircraft turns onto another heading.

A hand held compass, is unlikly to have such "local" interference, so can be adjusted for one known cardinal point and all the rest will line up - correct?

The aircraft compass will need to be checked/adjusted, every time there is a change to the panel or wiring behind ?

Hi Sean, yes I think you got it.  The changes are constant on the magnetic compass.  Indeed the "polar drift" of the magnetic north pole is up to 50 KM per year now.  As it drifts naturally the magnetic compass will always have errors and constantly require adjustments.  Aircraft versions are rather simple to adjust.  On ships, particularly big ones, we see large soft iron balls on adjustable slides, one on each side.  The also have a lot of deviations to correct for.  With our aircraft the engine, with the metal mounts and electrical parts, can also create a large draw on your magnetic compass.  There are a lot of very good source materials online on adjustment of the compass.  If it is just for decoration fine however I have had occasions when GPS failed and had to rely on my magnet antique on the dash, was happy it was there. 

So as you noted, for sure when you add or move things like a radio or new instrument you should check the calibration. 

Cheers

Sean,

Are you talking about a handheld compass MOUNTED in an aircraft? If so, it is subject to magnetic influence by its surroundings as any other compass. I don’t know how it could be adjusted for deviation unless you somehow use external magnets & or steel balls as per ships compasses as RW describes above. Correcting deviation is not just simply rotating the case to indicate a revised heading.

If it is truely hand held, I.e. free to be held in any orientation, there cannot be any way it can be “adjusted” for Deviation.

Polar drift affects Magnetic Variation (Declination) and cannot be adjusted out of a compass. This is accounted for in charting, both paper and electronic. Generally, this information (the WMM) is updated at 5 year intervals and applied to charts as a revision.

Structures and electro magnetic influences physically surrounding a compass affect Magnetic Deviation and can be adjusted within or adjacent to a compass depending on its type.

Cheers.

No Des, panel mounted aviation compass. I mentioned a hand held, for comparison only.😈