Compass swings.Basic question.

[ryandaum]

Hi guys,

I'm a new engineer and currently sitting my LAME exams. 2 years training at a school and have been with current company for 8 months.

If anyone has any links for helpful compass swing break downs that would be great.

My main question falls down to calculating residual deviations.
After the calibration swing we obviously have our deviations for N,NE,E,SE,S,SW,W,NW. Next we can calculate Coeff. A. from these numbers.

Now, where to from here?As I have received many different answers and the NZ LAME exam for compass swing requires 100% in 'To compass Swing' section.

Does coefficient A get applied to the deviations found on cardinal and quadrantal headings, or am I missing something? Once residual deviations are found, is it as simple as applying these to the steer by card?
I hope my questions make sense, I am going nuts trying to sort this as I want/need it down packed for my exam.:ugh:

Cheers to all in advance.
Ryan

[flame_bringer]

Compass Swing? — Tech Ops Forum | Airliners.net (http://www.airliners.net/aviation-forums/tech_ops/read.main/139038/)

Have a look at this thread.

[Gas Bags]

ryandaum,


Coefficient A is installation error and is corrected for by moving the compass about in its base.


(Please ignore the decimal points. Using them was the easy way to get the 4 to stay under the line!!)


Coefficient A = dev N + dev E + dev S + dev W
. . . . . . . . . . . . . . . . . . . . 4


example:


coefficient A = (+3 deg) + (+1 deg) + (-3 deg) + (+3 deg)
. . . . . . . . . . . . . . . . . . . . . . . . . 4


coefficient A = (+4 deg)
. . . . . . . . . . . . . 4


coefficient A = +1 degree


This resultant coefficient A is called the A error and is removed by loosening the compass mount fasteners and physically moving the compass in its mount.


You then have coefficient B and C to deal with which are corrected for by adjusting magnets integral to the compass.


After all that, the compass correction card is compiled that has the residual deviation at each 30 degree point marked on it.

[ryandaum]

Thanks for the replies.
So,
Residual deviation is calculated by adding coefficient A to the deviations found on the swing through cardinals and quadrantals?

[TinyTim2]

But be careful , direction is also critical .....A minus deviation is still minus , and minus / minus becomes plus .......