Remote Compass installation - accuracy

[chocks_away]

We are about to install the remote compass unit for our D100 in a Europa composite aircraft. Although it is not the easiest place for access, the rear fuselage seems the best location with no magnetic interference. We are having trouble working out how to install the unit so that it can be adjusted to align with the D100 to within 1 degree of accuracy - as the manual requests. In pitch and roll we can probably calibrate the position using our electronic spirit level - but we are not sure how to mount the compass so it can be finely adjusted. In yaw, all we can do is measure, but we are unlikely to achieve the accuracy needed. Is there a tried and tested method? Also, what will happen if the compass is not perfectly aligned with the D100?

 

[dynonsupport]

There is admittedly no tried and true method of assuring that the EDC is perfectly aligned with the EFIS in yaw. Just do the best you can by using points on the aircraft itself as a reference.

The calibration routine can take out small yaw errors, so this isn't a huge issue. The tilt and roll are the largest issues because the EFIS has to assume that the EDC is at the same angle unless we made you go out and fly a bunch of complex manuvers. The yaw can be calibrated out on the ground and thus that's what we do.

It works out kind of nicely that a level can help you set the two angles that we need the same but the one that can't be set with this method is the one we can calibrate out easily.

 

[Glastar1]

:-/ Gentlemen, my question relates to this task of alignment of the remote compass and the EFIS unit in my panel. I'm building a composite plane, a GlaStar, and the EFIS unit sits very near several steel tubes (elements of the cage) where the earth's field will be seriously distorted. Very much different from the quite uniform field at/near the top of the fuselage behind my baggage compartment. Doesn't this affect this alignment requiremet?
AND, is it my keyboard or is it this site that keeps dropping letters as I type?
Replies anxiously awaited. :-/
GlaStar1.

 

[dynonsupport]

The remote compass is just that- a compass that is away from the distortion that is in your panel. When using the remote compass, the EFIS unit doesn't do any detection of magnetic fields, so it doesn't matter how distorted the fields are around the EFIS.

In terms of alignment, I'm not sure what you mean. The EDC needs to be tilted at the same angle as the EFIS, but it can be anywhere in the plane that doesn't have much magnetic interference. The tail or wing works fine. It doesn't need to be in-line with the EFIS at all.

 

[Glastar1]

Dear DynonSupport:
Please check me out here: I suspect the important thing about the orientation of the remote unit is that it's axis coincide with the longitudinal axis of the airplane. That the orientation of the EFIS unit doesn't matter. It just reads the relationship between the horizontal component of the earth's field and the axis of the remote compass and displays that relationship. Am I right? If not, just what is going on?
GlaStar1

 

[dynonsupport]

The only thing that matters to the remote compass is that it is tilted at the same angle in pitch as the EFIS is, and that the "forward" direction is pointed in the direction the aircraft travels in. The magnetometer needs to be at the same angle as the EFIS because we pretend the EDC is inside the EFIS, and need to assume it's tilted the same way.

The magnetometer we use is a full, 3-axis magnetic field detector. In order to figure out which way is north, we use the three axis detector to "look" in the direction of the horizon, no matter what your pitch is. The compass works at any bank or pitch because it uses the EFIS horizon solution to determine what way to look. It works basically like a normal compass that is on a gyro so that the compass is always level with the horizon instead of pitching and rolling with the aircraft.

You don't need to align the EDC and EFIS in any axis of the aircaft. You just need to angle the EDC the same as the EFIS.

 

[Glastar1]

Hey, gotcha. Now it makes sense. Thanks a bunch.
Glastar1