Let me try again. I have a D10A and a D100, each have their own remote compasses which are mounted one on top of the other. After upgrading to 3.0 I swung the compasses using my King stone age whirling wheels gyro coupled to my Sandel as a reference. Previous measurements have shown the Sandel to be within one degree of the cardinal headings. After settnig up the Dynon units they where within a degree or two of the Sandel, I was pleased as Punch (an English outburst of positive emotion). I completed the condition inspection on my plane last week, a part of which was checking to see that the remote compass units weren't rattling about in the wingtip, they were there as snug as a bug. I flew about 2.5 hours this last weekend and noticed thet the two Dynon units were still within a degree of each other , but were 10 degrees out compared to the Sandel. Of course it must be the fault of the whirring wheels gyro! But NO!!! Rolling out on the runway the Sandel was about 3 dgrees off the runway heading and the Dynons were around 6 or 7. This error has been creeping up over time as I've noticed a slightly elevated error when compared to the Sandel, up to 5 or 6 degrees, but 10 degrees caught my attention. So I am now suspect that the Dynons my be incorrect. I know this is not an exhuastive test but on the surface things don't look too good. The puzzling thing is that the two Dynons are so close to each other. So if anyone has sage words regarding this I would appreciate reading them. Meantime when the weather clears I'll run off to a compass rose and check things more closely. The error was observed at a northerly and southerly heading (oubound and inbound from my trip)
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Re: Compass drift
- Thread starter N747PW
- Start date
Etienne
New Member
Are you sure there wasn't anything magnetic or metallic that was put temporarily near the remote compasses? Mine sits above and behind my baggage compartment, and I went on a nice long trip with a metal bicycle pump in the baggage compartment (about a meter away from the EDC) and it knocked my heading out by nearly 30 degrees.
After re-calibrating the compass with all the luggage in place, the compass worked flawlessly. After taking the baggage out again, the error was once again 30 degrees but in the opposite direction, which shows that the problem was indeed that pump. I have found that a normal compass isn't nearly this twitchy...
After re-calibrating the compass with all the luggage in place, the compass worked flawlessly. After taking the baggage out again, the error was once again 30 degrees but in the opposite direction, which shows that the problem was indeed that pump. I have found that a normal compass isn't nearly this twitchy...
My sensors are out in the wingtip, not much room for temporary stowage. There is an unlikely possibility that a magnet was placed near the sensors and then removed. Is there a possibility that a permanent change can be caused by such an event? This still doesn't explain the gradual deterioration of the accuracy though.
- Joined
- Mar 23, 2005
- Messages
- 13,226
If the magnetic environment around the EDC has changed since you calibrated it, you would definitely see an effect on heading. Additionally, a magnetic field induced by a magnet probably wouldn't cause permanent damage, unless it was a pretty strong magnet and placed pretty close to the EDC. Also, the application and removal of a magnetic field in the vicinity of the EDC should not change the calibration as long as that field is ultimately not there when you're flying.
Also, note that we have just released firmware version 4.0, which does change some small things about the way a calibration is treated.
What is your geographic location? And what are the values for inclination and intensity that you have been using to date?
Also, note that we have just released firmware version 4.0, which does change some small things about the way a calibration is treated.
What is your geographic location? And what are the values for inclination and intensity that you have been using to date?
meljordan
Active Member
I had the EDC mounted in my wingtip, but found it unsatisfactory for a couple of reasons. First, I could not get it far enough away from my NAV and Landing light wires. When I turned on either the NAV lights or the Landing light, I would get an error up to 15 degrees. Second, my aileron has an iron pipe in the leading edge as a counterweight. When I moved my ailerons up or down, it would influence my compass by a few degrees. I just could not get far enough away from the error sources in my wingtip. Please check that your EDC is not close to any wires that carry current to lights, and that there is nothing in the aileron that moves to cause and error. Just a couple of things to consider.
Best Regards,
Mel Jordan
RV-6A, Tucson
Best Regards,
Mel Jordan
RV-6A, Tucson
I am in Northern California near Sacramento. I will get the mag values used when I get home and post them. As I mentioned in the original post, I don;t think there was any magnetic field applied to the sensors. the installation hasn't changed since the calibration. Thanks for the help so far.
Pat
Pat