Magnetic field

[silvaleonardo]

Hello All.....I'm just about to install compass for backup but notice there is a magnetic field inside the cabin so it brings the compass a little off.
That problem has a solution or is a thing a have to live with it?
Thanks
Leonardo

[efwd]

I believe there is a solution. Compass heading correction card. Unfortunately I believe the magnetism is something you have to live with and correct for, with a little card attached to the compass informing you to fly 183` when wanting to track 180` for example. Obviously you have to limit your columns to 4 or five headings with their corresponding true number.

[Esser]

You can degaus your airframe which removes any magnetic field

[silvaleonardo]

You can degaus your airframe which removes any magnetic field

Josh....Excuse my ignorance but what is degaus and how you do it?

[efwd]

sure, doesn't account for avionics and electronics though.

[rv9ralph]

Remember in ground school when they were teaching compass. "East is least,West is best"
Also, variation and deviation. Deviation is the effect on a magnetic compass from things in its surroundings. This is adjustable by "swinging the compass" on a compass rose of known accuracy. There are 2 adjustment screws that allows most deviation to be reduced. After that, you need to move the aircraft through the different headings on the compass rose and noting the errors. This is then put on the compass correction card.

Note: use a brass or other not ferrous screwdriver to adjust the compass.

Ralph

ps - I always remember the difference between variation and deviation is the devious are all around you. And, Variation varies with location.

[efwd]

Thanks Ralph. I will admit that I kinda forgot about the brass screwdriver adjustment. I wasn't certain that it was an airplane compass we were talking about necessarily. Funny, in all the years I worked on helicopters, I can only recall doing a compass swing one time. The only time in 17 years I used that brass screwdriver.

[Esser]

Josh....Excuse my ignorance but what is degaus and how you do it?

I’m not super familiar with how. You’ll need to google that but basically it tries to remove as much of the magnetic field as possible with an electric current.

Basically you can rent a machine, you plug it into the wall, and you start going over your airframe in specific directions. It’s makes sure all the remaining magnetic field is all in the same direction. You can’t do this with instruments in as far as I know...

[Dave S]

Leonardo,


I had a problem like this in our S7 also.


Originally I wanted a vertical card compass, which I could not get corrected to any usable standard at all - older compass and not a very good compensating system.


I ended up visiting With John McBean on the issue - his first advice was to get one of the SIRS compasses - found one at Aircraft Spruce - I guess if they are good enough for Boeing, they might be good enough for a Kitfox. The basis for John's recommendation was that the SIRS has a superior compensating system - unlike my old VC compass. Another feature it has is an adjustable mount so you can make minor adjustments for pitch angle depending on loading.


Second issue - the kitfox airframe indeed has some residual magnetism; however, it is not the same in all parts of the cabin above the glareshield. Some experimenting established that where a compass is normally mounted, in the middle and above the panel, is the devil's triangle of the mother of all magnetic flux, at least on our plane. Also found that minimal interference occurred to the port and to the starboard side just above the corner of the panel. I mounted the SIRS on the port side as shown in the attached photo.


With the SIRS and with the location I was able to get a compensation in all directions less than 1 degree. I am happy with that plus not having to deal with other magnetic voodoo.


BTW - the SIRS comes with a non magnetic plastic key to set the compensation.

[jiott]

I installed a Falcon vertical card compass in the center top of my panel, just under the glare shield. Was able to use the compensating screws and get it to no more than about 2 degrees error.