Compass Swing

[N131MA]

On 9/23/2016 at 2:33 PM, M20Doc said:

In Canada we have to preform an annual magnetic compass swing, when doing that I note the Aspen compass as well.

Clarence

I recently recognized in flight that my Aspen compass was off 15 degrees and confirmed this using runway heading. Performing the Aspen magnetometer calibration procedure (start procedure in service menu, taxi in circles) got the magnetometer back on track.

[Marauder]

I recently recognized in flight that my Aspen compass was off 15 degrees and confirmed this using runway heading. Performing the Aspen magnetometer calibration procedure (start procedure in service menu, taxi in circles) got the magnetometer back on track.

Where did you get the service manual from?


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[N131MA]

10 hours ago, Marauder said:

 

Where did you get the service manual from?


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Downloaded from 

http://www.neboservice.ru/docs/0832502001214288299.pdf

ATC Ground asked me two times to confirm my intention to taxi in circles :-) 

[cliffy]

If any airport needs or wants a compass rose all they have to do is contact the nearest chapter of the 99s (girl's flying organization) 

Their public service is to paint new compass roses on airports. There will be a request to supply or pay for the paint and supplies (@$500) and have a surveyor shoot a magnetic north/south line on the ground where you want the rose. There are guidelines on where to place it but basically way out yonder on the airport and not over any underground voltage lines. 

We just did it here last summer. Had a commercial firm bid $6000 for what the 99s do for $500   We (our airport board) bought them lunch for both days also. 

A compass swing on a compass rose is a one man job. 

BTW, a bi-anneal compass swing is required on the Garmin panels also per their manual. 

[Conrad]

Well I got the swing accomplished. The entire procedure was done with a master compass, but there was no tripod involved, so I'm not sure how accurate I think it was. Sometimes the outside readings from the master compass seemed to agree perfectly with what the dg was telling me, but other times they seemed to disagree by 3-5 degrees. The deviations ranged from +6 to -10. If i did it again i think i'd just use the master for an initial heading and let the DG do the rest of the work.

[cliffy]

Just to be clear- normally a compass swing tries to remove as much error as possible but removing all error most of the time is not possible. A "master compass" usually is mounted on a gun stock type mount and the operator stands in front of the airplane "shooting" nose to tail for the reading'

The procedure goes something like this-

Line the airplane up on magnetic north (compass rose or master compass) and reset the aircraft compass with the N/S compensator to indicate exactlly north

Set the airplane up on east via the compass rose or MC and reset the "east/west" compensator to  exactly east on the airplane compass. 

Set the airplane up on south via the compass rose or MC and remove half of the shown error on the aircraft compass with the N/S compensator

Set up on west and remove half of the error shown also

Now start at north and go to every 30 degree cardinal heading on the compass rose or MC and record what is shown on the aircraft compass.

Technically no more than 10 degrees error is allowed at each cardinal heading.  43.13 has the entire procedure and it also says when a new swing should be done (outside of the airplane MM requirements). Even a hard landing is called out for a compass swing.  

Hope this helps.

 

[N201MKTurbo]

If you do the north south and east west adjustments a number of times, you can usually do better then just taking out half the error, but it takes a while. With one person with the master compass out in front of the plane and one person in the plane with the engine running, making taxi turns, you can do it rather quickly.