magnotometer placement

Any good gouge on magnotometer placement on an RV8? Was thinking out in the right wingR

Either there, or someway down the back of the fuselage e.g. the bulkhead behind the one with the bellcrank etc.

We've done the latter, works well, but NB the steel canopy frame goes a long way back when open... so do the calibration and only believe the reading with it shut

Andy
RV-8 G-HILZ
RV-8tors

Here's several replies from awhile back...

http://www.vansairforce.com/community/showthread.php?t=12051

fuselage works OK

I built a simple support near the first bulkhead aft of the rear baggage area using two aluminum angle braces attached. They bolt onto the longerons using one bolt on each end of each piece. Appears to work fine on my AFS system.
I avoided the wingtips due to all the stuff going on in each side- antennas, strobes, lights etc.
Tim

Magnometer - and ELT

I installed a lateral bracket to the top longerons behind the baggage bulkhead. Mounted both the ELT and magnometer on it.

I installed mine out in the wingtip.

My thinking was: many certified installations have it out there.

One problem: when I turn on the wingtip landing light in that wing, it slews the heading.

Strobes, nav lights don't affect it, just the landing light.

Keep the wiring for the magnetometer separated from the landing light wires.

This would probably apply if you mounted the magnetometer in the fuselage as well, if the landing light wires happened to be close to a portion of the magnetometer wires.

Craig said:

I installed mine out in the wingtip.

My thinking was: many certified installations have it out there.

One problem: when I turn on the wingtip landing light in that wing, it slews the heading.

Strobes, nav lights don't affect it, just the landing light.

Keep the wiring for the magnetometer separated from the landing light wires.

This would probably apply if you mounted the magnetometer in the fuselage as well, if the landing light wires happened to be close to a portion of the magnetometer wires.

Click to expand...

It's not the proximity of the magnetometer wires to the landing light wires that's the problem, It's the proximity of the landing light wire to the magnetometer itself. My guess is that you have grounded the landing light to the wing spar and have a single wire driving the lamp. The relatively large current of 7-10 amps, returning in the spar provides a large loop of current. This creates a substantial ambient magnetic field, upsetting the magnetometer.

Having a separate ground return, running parallel with the landing light wire (or better yet, twisted with it) will reduce the interference. The magnetic field is concentrated in the space between the wires, hence ambient fields are much smaller in this configuration than the single wire configuration returning on the spar.

V

Thanks Vern, I'll try it.

Carlos at Grand Rapids had me try a filter that plugs into the magnetometer. That didn't help.

It's nine months later now, and I've had the airplane down for it's first annual. While it was down, I decided to fix the problem with interference between the magnetometer and left landing light.

I tried running a separate ground from the landing light to the common grounding point by the battery. No effect.

I considered running the magnetometer wire bundle in a separate run out to the magnetometer in the left wingtip. That seemed to be too much work in a finished wing.

I decided to relocate the magnetometer to the aft section of the fuselage, where a lot of other people have put it. That way, I could keep the wires separate from almost everything. I also put a shield around the bundle of wires and grounded that to the main grounding panel by the battery.

It all works now. No heading swings with any device.

Thanks for that feedback, Craig. Good to know.

--
Joe